ALBERT

Beschreibung: 〈b〉Induced seismicity in geologic carbon storage〈/b〉〈br〉 Víctor Vilarrasa, Jesus Carrera, Sebastià Olivella, Jonny Rutqvist, and Lyesse Laloui〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-129,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 To meet the goal of the Paris Agreement to limit temperature increase below 2 ºC, Geologic Carbon Storage (GCS) will be necessary at the gigatone scale. But to successfully deploy GCS, seismicity induced by CO〈sub〉2〈/sub〉 injection should be controlled and maintained below a threshold that does not generate nuisances to the population. We conclude that felt induced seismicity can be minimized provided that a proper site characterization, monitoring and pressure management are performed.

Beschreibung: 〈b〉Seismic Hazard of L'Aquila downtown (central Italy): new insights for 3D geological model based on high-resolution seismic reflection profile and borehole stratigraphy〈/b〉〈br〉 Marco Tallini, Marco Spadi, Domenico Cosentino, Marco Nocentini, Luca Macerola, Giuseppe Cavuoto, and Vincenzo Di Fiore〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-25,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 The interpretation of a 1 km-long high-resolution seismic reflection profile integrated with borehole stratigraphy was useful to reconstruct the geological subsoil model of L'Aquila downtown which was struck by the 6/4/2009 Mw 6.1 earthquake, and thus to provide indication on the seismic site effects and the faults activity. This information was essential to design urban masterplan able to mitigate the Seismic Hazard of cultural heritage cities of central Italy, such as the case study site.

Beschreibung: 〈b〉Precision of continuous GPS velocities from statistical analysis of synthetic time series〈/b〉〈br〉 Christine Masson, Stephane Mazzotti, and Philippe Vernant〈br〉 Solid Earth, 10, 329-342, https://doi.org/10.5194/se-10-329-2019, 2019〈br〉 We use statistical analyses of synthetic position time series to estimate the potential precision of GPS velocities. Regression tree analyses show that the main factors controlling the velocity precision are the duration of the series, the presence of offsets, and the noise. Our analysis allows us to propose guidelines which can be applied to actual GPS data that constrain the velocity accuracies.

Beschreibung: 〈b〉The Geodynamic World Builder: a solution for complex initial conditions in numerical modelling〈/b〉〈br〉 Menno Fraters, Cedric Thieulot, Arie van den Berg, and Wim Spakman〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-24,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Three-dimensional numerical modelling of geodynamic processes may benefit strongly from using realistic 3D starting models that approximate e.g. natural subduction settings in the geological past or at present. To this end we developed the Geodynamic World Builder (GWB) which enables relatively straight-forward parameterization of complex 3D geometric structures associated with geodynamic processes. The GWB is an open source community code designed to easily interface with geodynamic codes.

Beschreibung: 〈b〉Improving quality of empirical Greens functions, obtained by cross-correlation of high-frequency ambient seismic noise〈/b〉〈br〉 Nikita Afonin, Elena Kozlovskaya, Jouni Nevalainen, and Janne Narkilahti〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-29,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Studying the uppermost structure of the subsurface is a necessary part for solving many practical problems (exploration of minerals, groundwater studies, geoengineering, etc.). Practical application of active seismic methods is not always possible because of different reasons, such as logistical difficulties, high cost of work, high level of seismic and acoustic noise, etc. That is why developing and improving of passive seismic methods for these purposes is one of the important problems in applied geophysics. In our study, we describe the way of improving quality of Empirical Green’s Functions (EGFs), evaluated from high-frequency ambient seismic noise, by using of advanced technique of cross-correlation functions stacking in the time domain (in this paper we use term “high-frequency” for the frequencies higher than 1 Hz). In compare to existing techniques, based on weight-stacking, our proposed technique makes it possible to more significantly increase the signal-to-noise ratio and, therefore quality of the EGF. The technique is based on both iterative and global optimization algorithms, where the optimized parameter is a signal-to-noise ratio of an EGF, retrieved for each iteration. The technique has been tested with the field data acquired in an area with high level of industrial noise (Pyhäsalmi Mine, Finland) and in an area with low level of anthropogenic noise (Kuusamo Greenstone Belt, Finland). The results show that the our proposed technique can be used for extraction of EGFs from high-frequency seismic noise in practical problems of mapping of the shallow subsurface in areas with high and low level of high-frequency seismic noise.〈/p〉

Beschreibung: 〈b〉Event couple spectral ratio 〈i〉Q〈/i〉 method for earthquake clusters: application to northwest Bohemia〈/b〉〈br〉 Marius Kriegerowski, Simone Cesca, Matthias Ohrnberger, Torsten Dahm, and Frank Krüger〈br〉 Solid Earth, 10, 317-328, https://doi.org/10.5194/se-10-317-2019, 2019〈br〉 We developed a method that allows to estimate the acoustic attenuation of seismic waves within regions with high earthquake source densities. Attenuation is of high interest as it allows to draw conclusions on the origin of seismic activity. We apply our method to north-west Bohemia, which is regularly affected by earthquake swarms during which thousands of earthquakes are registered within a few days. We find reduced attenuation within the active volume, which may indicate high fluid content.

Beschreibung: 〈b〉Constraining metamorphic dome exhumation and fault activity through hydrothermal monazite-(Ce)〈/b〉〈br〉 Christian A. Bergemann, Edwin Gnos, Alfons Berger, Emilie Janots, and Martin J. Whitehouse〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-10,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Zoned monazite-(Ce) from Alpine fissures/clefts is used to gain new insights into the exhumation history of the Central Alpine Lepontine metamorphic dome, and timing of deformation along the Rhone-Simplon fault zone on the dome's western termination. These hydrothermal monazites-(Ce) directly date deformation and changes in physiochemical conditions through crystallization ages, in contrast to commonly employed cooling-based methods. The 480 SIMS measurement ages from 20 individual crystals record ages over a time interval between ~ 19 and 5 Ma, with individual grains recording ages over a lifetime of 2 to 7.5 Ma. The age range combined with age distribution and internal crystal structure help to distinguish between areas whose deformational history was dominated by distinct tectonic events or continuous exhumation. The combination of this age data with geometrical considerations and spatial distribution give a more precise exhumation/cooling history for the area. In the east and south of the study region, the units underwent monazite-(Ce) growth at 19–12.5 and 16.5–10.5 Ma, followed by a central group of monazite-(Ce) ages at 15–10 Ma and the movements and related cleft monazites-(Ce) are youngest at the western border with 13–7 Ma. A last phase around 8–7 Ma is limited to clefts of the Simplon normal fault and related strike slip faults as the Rhone and Rhine-Rhone faults. The large data-set spread over significant metamorphic structures shows that the opening of clefts, fluid flow and monazite-(Ce) stability is direct linked to the geodynamic evolution in space and time.

Beschreibung: 〈b〉Slab Break-offs in the Alpine Subduction Zone〈/b〉〈br〉 Emanuel D. Kästle, Claudio Rosenberg, Lapo Boschi, Nicolas Bellahsen, Thomas Meier, and Amr El-Sharkawy〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-17,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 We provide an extensive comparison of high-resolution subsurface models of the Alpine subduction zone. The imaged slab geometries are discussed in relation to the geodynamic evolution of the Alpine region. In the eastern Alps, we compare the models to three scenarios from the literature and propose a fourth one which best fits the tomographic images and the geological constraints. We find that the European slab is broken off below the entire Alpine arc, at variable depth levels.

Beschreibung: 〈b〉Structural expression of a fading rift front: a case study from the Oligo-Miocene Irbid rift of northwest Arabia〈/b〉〈br〉 Reli Wald, Amit Segev, Zvi Ben-Avraham, and Uri Schattner〈br〉 Solid Earth, 10, 225-250, https://doi.org/10.5194/se-10-225-2019, 2019〈br〉 Plate-scale rifting is frequently expressed by the subsidence of structural basins along an axis, but postdating tectonic and magmatic activity mostly obscures them. A 3-D subsurface imaging and facies analysis down to 1 km reveals uniquely preserved Galilean basins subsiding along a failing rift front in two main stages. Rifting within a large releasing jog (20–9 Ma), followed by localized grabenization off the Dead Sea fault plate boundary (9–5 Ma), prevents them from dying out peacefully.

Beschreibung: 〈b〉Distinct Element geomechanical modelling of the formation of sinkhole cluster within large-scale karstic depressions〈/b〉〈br〉 Djamil Al-Halbouni, Eoghan P. Holohan, Abbas Taheri, Robert A. Watson, Ulrich Polom, Martin P. J. Schöpfer, Sacha Emam, and Torsten Dahm〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-20,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 A 2D numerical modelling approach to simulate the mechanical formation of sinkhole cluster inside large-scale karstic depressions is presented. Different multiple cavity growth scenarios at depth are compared regarding the mechanical process and collapse style. The outcomes of the models are compared to results from remote sensing and geophysics for an active sinkhole area at the Dead Sea region.

Beschreibung: 〈b〉Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature〈/b〉〈br〉 Junichi Fukuda, Hugues Raimbourg, Ichiko Shimizu, Kai Neufeld, and Holger Stünitz〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-13,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉The grain growth of quartz was investigated using two samples of quartz (powder and quartzite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 °C. The compacted powder preserved a large porosity, which caused a slower grain growth than in the dense quartzite. We assumed a grain-growth law of 〈i〉d〈sup〉n〈/sup〉〈/i〉-〈i〉d〈sub〉0〈/sub〉〈sup〉n〈/sup〉〈/i〉 = 〈i〉k〈/i〉〈sub〉0〈/sub〉 〈i〉f〈/i〉〈sub〉H〈sub〉2〈/sub〉O〈/sub〉〈sup〉〈i〉r〈/i〉〈/sup〉 exp⁡(−〈i〉Q〈/i〉/〈i〉RT〈/i〉)〈i〉t〈/i〉 with grain size 〈i〉d〈/i〉 (µm) at time 〈i〉t〈/i〉 (second), initial grain size 〈i〉d〈sub〉0〈/sub〉〈/i〉 (µm), growth exponent 〈i〉n〈/i〉, a constant 〈i〉k〈sub〉0〈/sub〉〈/i〉 (µm〈sup〉〈i〉n〈/i〉〈/sup〉 MPa〈sup〉−〈i〉r〈/i〉〈/sup〉 s〈sup〉−1〈/sup〉), water fugacity 〈i〉f〈/i〉〈sub〉H〈sub〉2〈/sub〉O〈/sub〉 (MPa) with the exponent 〈i〉r〈/i〉, activation energy 〈i〉Q〈/i〉 (kJ/mol), gas constant 〈i〉R〈/i〉, and temperature 〈i〉T〈/i〉 in Kelvin. The parameters we obtained were 〈i〉n〈/i〉 = 2.5 ± 0.4, 〈i〉k〈/i〉〈sub〉0〈/sub〉 = 10〈sup〉−8.8 ± 1.4〈/sup〉, 〈i〉r〈/i〉 = 2.3 ± 0.3, and 〈i〉Q〈/i〉 = 48 ± 34 for the powder, and 〈i〉n〈/i〉 = 2.9 ± 0.4, 〈i〉k〈/i〉〈sub〉0〈/sub〉 = 10〈sup〉−5.8 ± 2.0〈/sup〉, 〈i〉r〈/i〉 = 1.9 ± 0.3, and 〈i〉Q〈/i〉 = 60 ± 49 for the quartzite. The grain-growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks, even if the differences between powder and quartzite vanish when grain sizes reach ~ 70 µm. Extrapolation of the grain-growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is −12/s.〈/p〉

Beschreibung: 〈b〉Integration of geoscientific uncertainty into geophysical inversion by means of local gradient regularization〈/b〉〈br〉 Jeremie Giraud, Mark Lindsay, Vitaliy Ogarko, Mark Jessell, Roland Martin, and Evren Pakyuz-Charrier〈br〉 Solid Earth, 10, 193-210, https://doi.org/10.5194/se-10-193-2019, 2019〈br〉 We propose the quantitative integration of geology and geophysics in an algorithm integrating the probability of observation of rocks with gravity data to improve subsurface imaging. This allows geophysical modelling to adjust models preferentially in the least certain areas while honouring geological information and geophysical data. We validate our algorithm using an idealized case and apply it to the Yerrida Basin (Australia), where we can recover the geometry of buried greenstone belts.

Beschreibung: 〈b〉Uniaxial compression of calcite single crystals at room temperature: insights into twinning activation and development〈/b〉〈br〉 Camille Parlangeau, Alexandre Dimanov, Olivier Lacombe, Simon Hallais, and Jean-Marc Daniel〈br〉 Solid Earth, 10, 307-316, https://doi.org/10.5194/se-10-307-2019, 2019〈br〉 Calcite twinning is a common deformation mechanism that mainly occurs at low temperatures. Twinning activation appears at a critical strength value, which is poorly documented and still debated. Temperature is known to influence twin thickness and shape; however, few studies have been conducted on calcite deformation at low temperatures. The goal of this work is to determine if thickness is mainly due to high temperatures and to establish the validity of a threshold twinning activation value.

Beschreibung: 〈b〉Impact of terrestrial reference frame realizations on altimetry satellite orbit quality and global and regional sea level trends: a switch from ITRF2008 to ITRF2014〈/b〉〈br〉 Sergei Rudenko, Saskia Esselborn, Tilo Schöne, and Denise Dettmering〈br〉 Solid Earth, 10, 293-305, https://doi.org/10.5194/se-10-293-2019, 2019〈br〉 A terrestrial reference frame (TRF) realization is a basis for precise orbit determination of Earth-orbiting artificial satellites and sea level studies. We investigate the impact of a switch from an older TRF realization (ITRF2008) to a new one (ITRF2014) on the quality of orbits of three altimetry satellites (TOPEX/Poseidon, Jason-1, and Jason-2) for 1992–2015, but especially from 2009 onwards, and on altimetry products computed using the satellite orbits derived using ITRF2014.

Beschreibung: 〈b〉Subsurface structures of a quick-clay sliding prone area revealed using land-river reflection seismic data and hydrogeological modelling〈/b〉〈br〉 Silvia Salas-Romero, Alireza Malehmir, Ian Snowball, and Benoît Dessirier〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-22,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Land-river reflection seismic, hydrogeological modelling, and magnetic investigations in an area prone to quick-clay landslides in SW Sweden provide a detailed description of the subsurface structures, such as undulating fractured bedrock, and a sedimentary sequence of intercalating leached and unleached clay, and coarse-grained deposits. Hydrological properties of the coarse-grained layer help understanding its role in the leaching process that leads to the formation of quick clays in the area.

Beschreibung: 〈b〉Power spectra of random heterogeneities in the solid earth〈/b〉〈br〉 Haruo Sato〈br〉 Solid Earth, 10, 275-292, https://doi.org/10.5194/se-10-275-2019, 2019〈br〉 Recent seismological observations clarified that the velocity structure of the crust and upper mantle is randomly heterogeneous. I compile reported power spectral density functions of random velocity fluctuations based on various types of measurements. Their spectral envelope is approximated by the third power of wavenumber. It is interesting to study what kinds of geophysical processes created such a power-law spectral envelope at different scales and in different geological environments.

Beschreibung: 〈b〉Deformation mechanisms in mafic amphibolites and granulites: record from the Semail metamorphic sole during subduction infancy〈/b〉〈br〉 Mathieu Soret, Philippe Agard, Benoît Ildefonse, Benoît Dubacq, Cécile Prigent, and Claudio Rosenberg〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-28,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 This study sheds light on the mineral-scale mechanisms controlling the progressive deformation of sheared amphibolites from the Oman metamorphic sole during subduction initiation, and unravels how strain is localized and accommodated in (hydrated) mafic rocks at high temperature conditions. Our results indicate how metamorphic reactions and pore-fluid pressures driven by changes in pressure–temperature conditions and/or water activity control the rheology of mafic rocks.

Beschreibung: 〈b〉The building, shaping, and filling of an Upper Slope Terrace: the Rio Grande Terrace, SW Atlantic〈/b〉〈br〉 Michel Michaelovitch de Mahiques, Javier Alcántara-Carrió, Francisco José Lobo, Uri Schattner, Rosangela Felício dos Santos, Samara Cazzoli y Goya, Raissa Basti Ramos, José Gustavo Natorf de Abreu, Luiz Antonio Pereira de Souza, Rubens Cesar Lopes Figueira, and Marcia Caruso Bícego〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-140,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 This paper is a contribution to the knowledge of the geological processes on the SW Atlantic. We tried to integrate data from different time-scales, such as the geological evolution (millions of years) to the hydrodynamic processes (days to years). The results allowed us to recognize the importance of the geological inheritance to the present morphology of submerged areas.

Beschreibung: 〈b〉Petrographic and Petrophysical Characteristics of Lower Cretaceous Sandstones from northern Israel, determined by micro-CT imaging and analytical techniques〈/b〉〈br〉 Peleg Haruzi, Regina Katsman, Baruch Spiro, Matthias Halisch, and Nicolas Waldmann〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-21,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 We studied petrophysical characteristics of three consecutive sandstone layers of the Lower Cretaceous Hatira Formation from Israel. Evaluated micro- and macro-scale petrophysical properties predetermined the permeability of the layers, measured in turn in the lab and upscaled from pore-scale velocities. Two scales of porosity variations were found: at 300 μm scale due to pores size variability, and at 2 mm scale due to high and low porosity occlusions, suggested to control the permeability.

Beschreibung: 〈b〉Granite microporosity changes due to fracturing and alteration: secondary mineral phases as proxies for porosity and permeability estimation〈/b〉〈br〉 Martin Staněk and Yves Géraud〈br〉 Solid Earth, 10, 251-274, https://doi.org/10.5194/se-10-251-2019, 2019〈br〉 Granite is suitable to host geothermal wells or disposals of hazardous waste and in these cases the rock porosity and permeability are critical. Our detailed porosity and permeability data on variously deformed Lipnice granite yield a span of 5 orders of magnitude in permeability between the least and the most deformed facies. To facilitate the estimation of porosity and permeability in similar settings, we provide optical and chemical data on the characteristic minerals of each facies.

Beschreibung: 〈b〉On the link between Earth tides and volcanic degassing〈/b〉〈br〉 Florian Dinger, Stefan Bredemeyer, Santiago Arellano, Nicole Bobrowski, Ulrich Platt, and Thomas Wagner〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-14,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Evidences for tidal impacts on volcanism have been gathered by numerous empirical studies. This paper elucidates whether a causal link from the tidal forces to a variation in the volcanic degassing can be traced analytically. We model the response of a simplified magmatic system to the local tidal gravity variations, find that the tide-induced dynamics may significantly alter the bubble coalescence rate, and discuss the consequences for the volcanic degassing behaviour.

Beschreibung: 〈b〉Fault-controlled dolomitization in the Montagna dei Fiori Anticline (Central Apennines, Italy): Record of a dominantly pre-orogenic fluid migration〈/b〉〈br〉 Mahtab Mozafari, Rudy Swennen, Fabrizio Balsamo, Hamdy El Desouky, Fabrizio Storti, and Conxita Taberner〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-136,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 The dolomitized intervals of the Lower Jurassic deposits exposed in the Montagna dei Fiori Anticline (Central Apennines, Italy) have been investigated. Accordingly, two fault-related dolomitization events were recognised and interpreted as occurred before and during the Apenninic orogeny, respectively. The analyses suggest significant involvement of evaporitic fluids in both events, most likely derived from the underlying Upper Triassic Burano Formation in the detachment level.

Beschreibung: 〈b〉Moment magnitude estimates for Central Anatolian earthquakes using coda waves〈/b〉〈br〉 Tuna Eken〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-8,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Proper magnitude estimates for earthquakes can give an insight into the seismic energy released at earthquake source. This is, in fact, essential for better seismic hazard assessments in tectonically active regions. In the present work, I examine local earthquakes in central Anatolia to estimate their moment magnitudes. The main outcome of this study is an empirical relation that can provide a direct physical quantity of seismic energy in the study region.

Beschreibung: 〈b〉Fluid-mediated, brittle-ductile deformation at seismogenic depth: Part I – Fluid record and deformation history of fault-veins in a nuclear waste repository (Olkiluoto Island, Finland)〈/b〉〈br〉 Barbara Marchesini, Paolo Stefano Garofalo, Luca Menegon, Jussi Mattila, and Giulio Viola〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-5,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 1 comment)〈br〉 The influence of fluids on the initiation and evolution of faults at the brittle ductile transition is still underdocumented. We studied the rocks of a deeply exhumed fault characterized by mixed brittle-ductile deformation. The chemistry of synkinematic fluids trapped in the crystals and thermobarometic estimates highlighted several cycles of fluid pressure and stress fluctuations that caused the initial faulting and its following structural evolution.

Beschreibung: 〈b〉Green's theorem in seismic imaging across the scales〈/b〉〈br〉 Kees Wapenaar, Joeri Brackenhoff, and Jan Thorbecke〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-141,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 The solid earth and exploration communities independently developed a variety of seismic imaging methods for passive- and active-source data. Despite the seemingly different approaches and underlying principles, many of those methods are based in some way or another on the same mathematical theorem. Starting with this theorem, we discuss a variety of classical and recent seismic imaging methods in a systematic way and explain their similarities and differences.

Beschreibung: 〈b〉A multi-technology analysis of the 2017 North Korean nuclear test〈/b〉〈br〉 Peter Gaebler, Lars Ceranna, Nima Nooshiri, Andreas Barth, Simone Cesca, Michaela Frei, Ilona Grünberg, Gernot Hartmann, Karl Koch, Christoph Pilger, J. Ole Ross, and Torsten Dahm〈br〉 Solid Earth, 10, 59-78, https://doi.org/10.5194/se-10-59-2019, 2019〈br〉 On 3 September 2017 official channels of the Democratic People’s Republic of Korea announced the successful test of a nuclear device. This study provides a multi-technology analysis of the 2017 North Korean event and its aftermath using a wide array of geophysical methods (seismology, infrasound, remote sensing, radionuclide monitoring, and atmospheric transport modeling). Our results clearly indicate that the September 2017 North Korean event was in fact a nuclear test.

Beschreibung: 〈b〉ER3D: a structural and geophysical 3D model of central Emilia-Romagna (Northern Italy) for numerical simulation of earthquake ground motion〈/b〉〈br〉 Peter Klin, Giovanna Laurenzano, M. Adelaide Romano, Enrico Priolo, and Luca Martelli〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-1,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Using geological and geophysical data we set-up a 3D digital description of the underground structure in the central part of the Po alluvial plain. By means of computer simulated propagation of seismic waves we were able to identify the structural features that caused the unexpected elongation and amplification of the earthquake ground motion that was observed in the area during the 2012 seismic crisis. The study permits a deeper understanding of the seismic hazard in alluvial basins.

Beschreibung: 〈b〉Bayesian geological and geophysical data fusion for the construction and uncertainty quantification of 3D geological models〈/b〉〈br〉 Hugo K. H. Olierook, Richard Scalzo, David Kohn, Rohitash Chandra, Ehsan Farahbakhsh, Gregory Houseman, Chris Clark, Steven M. Reddy, and R. Dietmar Müller〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-4,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Traditional approaches to develop 3D geological models employ a mix of quantitative and qualitative scientific techniques, which do not fully provide quantification of uncertainty in the constructed models and fail to optimally weight geological field observations against constraints from geophysical data. Here, we demonstrate a Bayesian methodology to fuse geological field observations with aeromagnetic and gravity data to build robust 3D models in a 13.5 × 13.5 km region of the Gascoyne Province, Western Australia. Our approach is validated by comparing model results to independently-constrained geological maps and cross-sections produced by the Geological Survey of Western Australia. By fusing geological field data with magnetics and gravity surveys, we show that at 89 % of the modelled region has 〉 95 % certainty. The boundaries between geological units are characterized by narrow regions with 〈/p〉

Beschreibung: 〈b〉A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi〈/b〉〈br〉 Michael Hodge, Juliet Biggs, Åke Fagereng, Austin Elliott, Hassan Mdala, and Felix Mphepo〈br〉 Solid Earth, 10, 27-57, https://doi.org/10.5194/se-10-27-2019, 2019〈br〉 This work attempts to create a semi-automated algorithm (called SPARTA) to calculate height, width and slope of surface breaks produced by earthquakes on faults. We developed the Python algorithm using synthetic catalogues, which can include noise features such as vegetation, hills and ditches, which mimic natural environments. We then apply the algorithm to four fault scarps in southern Malawi, at the southern end of the East African Rift system, to understand their earthquake potential.

Beschreibung: 〈b〉Spatio-temporal dynamics of sediment transfer systems in landslide-prone alpine catchments〈/b〉〈br〉 François Clapuyt, Veerle Vanacker, Fritz Schlunegger, Marcus Christl, and Kristof Van Oost〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-139,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 In mountainous environments, landslides act as stochastic but discrete sediment sources in the landscape and randomly affect these catchments. Our study highlights that at the regional scale, one single landslide has not necessarily an impact on landscape evolution. It is the integrated effect of multiple sediment pulses providing sediments to the river network at the decadal scale, which are subsequently attenuated by sediment transport that may regulate sediment fluxes at the regional scale.

Beschreibung: 〈b〉Improving subduction interface implementation in dynamic numerical models〈/b〉〈br〉 Dan Sandiford and Louis Moresi〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-11,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This study focuses on methodological issues related to dynamic subduction zone modelling. Numerical models often employ an entrained weak layer (WL approach) to facilitate decoupling between the subducting and overriding plates. In such a setup, the kinematics of the flow lead to width variations in the subduction interface. When a uniform-width interface is prescribed, a transient evolution of the interface thickness occurs, during which the volmetric flux along the interface profile establishes equilibrium. Width variations can exceed 4× during this stage, which may impact the effective strength of the interface, both through physical effects if the rheology is linear, and numerical effects if the fault becomes poorly resolved. This transient process induces strong sensitivity to model resolution, and may present a significant challenge to reproducibility. Developing more robust ways to model the subduction interface will enable fully dynamic models to address sensitive subduction-zone processes, such as metamorphism near the slab top. In this study we discuss a simple strategy aimed at improving the standard WL approach. By prescribing a variable thickness weak layer at the outset of the model, and by controlling the limits of the layer thickness during the model evolution, we find improved stability and resolution convergence of the models.〈/p〉

Beschreibung: 〈b〉Geochronological and thermometric evidence of unusually hot fluids in an Alpine fissure of Lauzière granite (Belledonne, Western Alps)〈/b〉〈br〉 Emilie Janots, Alexis Grand'Homme, Matthias Bernet, Damien Guillaume, Edwin Gnos, Marie-Christine Boiron, Magali Rossi, Anne-Magali Seydoux-Guillaume, and Roger De Ascenção Guedes〈br〉 Solid Earth, 10, 211-223, https://doi.org/10.5194/se-10-211-2019, 2019〈br〉 This geochronological and thermometric study reveals unusually hot fluids in an Alpine-type fissure of granite from the external crystalline massif (Western Alps). The fluid is estimated to be 150-250 °C hotter than the host rock and requires a dynamic fluid pathway at mid-crustal conditions in the ductile regime. This fluid circulation resets the zircon fission track thermochronometer, but only at the fissure contact. Thermal disturbances due to advective heating appear to be localized.

Beschreibung: 〈b〉Monitoring induced distributed double-couple sources using Marchenko-based virtual receivers〈/b〉〈br〉 Joeri Brackenhoff, Jan Thorbecke, and Kees Wapenaar〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-142,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Earthquakes in the subsurface are hard to monitor due to their complicated signals. We aim to make the monitoring of the subsurface possible by redatuming the sources and the receivers from the surface of the Earth to the subsurface to monitor earthquakes originating from small faults in the subsurface. By using several sources together, we create complex earthquake signals for large scale faults sources.

Beschreibung: 〈b〉Deformation of feldspar at greenschist facies conditions – the record of mylonitic pegmatites from the Pfunderer Mountains, Eastern Alps〈/b〉〈br〉 Felix Hentschel, Claudia A. Trepmann, and Emilie Janots〈br〉 Solid Earth, 10, 95-116, https://doi.org/10.5194/se-10-95-2019, 2019〈br〉 We used microscopy and electron backscatter diffraction to analyse the deformation behaviour of feldspar at greenschist facies conditions in mylonitic pegmatites of the Austroalpine basement. There are strong uncertainties about feldspar deformation, mainly because of the varying contributions of different deformation processes. We observed that deformation is mainly the result of coupled fracturing and dislocation glide, followed by growth and granular flow.

Beschreibung: 〈b〉Topographic changes due to the 2004 Chuetsu thrusting earthquake in low mountain region〈/b〉〈br〉 Zhikun Ren, Takashi Oguchi, Peizhen Zhang, and Shoichiro Uchiyama〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-3,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 This research might be the first time to study the topographic changes due to strong earthquakes in region of low relief. We use high-resolution pre- and post-earthquake DEMs to detect the topographic changes caused by the Wenchuan earthquake. However, the topographic changes caused by the Chuetsu earthquake is different. Our findings might indicate that the earthquake mainly acts as roughening and driving the topographic growth in region of low relief.

Beschreibung: 〈b〉Electrical Formation Factor of Clean Sand from Laboratory Measurements and Digital Rock Physics〈/b〉〈br〉 Mohammed Ali Garba, Stephanie Vialle, Mahyar Madadi, Boris Gurevich, and Maxim Lebedev〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-133,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 1 comment)〈br〉 〈p〉Electrical properties of rocks are important parameters for well-log and reservoir interpretation. Laboratory measurements of such properties are time-consuming, difficult, and are impossible in some cases. Being able to compute them from 3-D images of small samples will allow generating massive data in a short time, opening new avenues in applied and fundamental science. To become a reliable method, the accuracy of this technology needs to be tested. In this study, we developed a comprehensive and robust workflow with clean sand from two beaches. Electrical conductivities at 1 kHz were first carefully measured in the laboratory. A range of porosities spanning from a minimum of 0.26 to 0.33 to a maximum of 0.39 to 0.44, depending on the samples. Such range was achieved by compacting the samples in a way that reproduces natural packing of sand. Characteristic electrical formation factor versus porosity relationships were then obtain for each sand type. 3-D micro-computed tomography images of each sand sample from the experimental sand pack were acquired at different resolutions. Image processing was done using global thresholding method and up to 96 sub-samples of sizes from (200)〈sup〉3〈/sup〉 to (700)〈sup〉3〈/sup〉 voxels. After segmentation, the images were used to compute the effective electrical conductivity of the sub-cubes using a Finite Element electrostatic modelling. For the samples, a good agreement between laboratory measurements and computation from digital cores was found, if the sub-cube size REV is reached that is between (1300 μm)〈sup〉3〈/sup〉 and (1820 μm)〈sup〉3〈/sup〉, which, with an average grain size of 160 μm, is between 8 and 11 grains. Computed digital rock images of the clean sands have opened a way forward in getting the formation factor within a shortest possible time; laboratory calculations take five (5) to thirty-five (35) days as in the case of clean and shaly sands respectively, whereas, the digital tomography takes just three (3) to five (5) hours.〈/p〉

Beschreibung: 〈b〉3-D seismic travel-time tomography validation of a detailed subsurface model: a case study of the Záncara river basin (Cuenca, Spain)〈/b〉〈br〉 David Marti, Ignacio Marzan, Jana Sachsenhausen, Joaquina Alvarez-Marrón, Mario Ruiz, Montse Torne, Manuela Mendes, and Ramon Carbonell〈br〉 Solid Earth, 10, 177-192, https://doi.org/10.5194/se-10-177-2019, 2019〈br〉 A detailed knowledge of the very shallow subsurface has become of crucial interest for modern society, especially if it hosts critical surface infrastructures such as temporary waste storage sites. The use of indirect methods to characterize the internal structure of the subsurface has been successfully applied, based on the 3-D distribution of seismic velocities and well-log data, which are of great interest for civil engineering companies.

Beschreibung: 〈b〉Tectono-thermal evolution of Oman's Mesozoic passive continental margin under the obducting Semail Ophiolite: a case study of Jebel Akhdar, Oman〈/b〉〈br〉 Arne Grobe, Christoph von Hagke, Ralf Littke, István Dunkl, Franziska Wübbeler, Philippe Muchez, and Janos L. Urai〈br〉 Solid Earth, 10, 149-175, https://doi.org/10.5194/se-10-149-2019, 2019〈br〉 The Mesozoic sequences of the Oman mountains experienced only weak post-obduction overprint and deformation, and thus they offer a unique natural laboratory to study obduction. We present a study of pressure and temperature evolution in the passive continental margin under the Oman Ophiolite using numerical basin models calibrated with thermal maturity data, fluid-inclusion thermometry, and low-temperature thermochronology.

Beschreibung: 〈b〉Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision〈/b〉〈br〉 Carly Faber, Holger Stünitz, Deta Gasser, Petr Jeřábek, Katrin Kraus, Fernando Corfu, Erling K. Ravna, and Jiří Konopásek〈br〉 Solid Earth, 10, 117-148, https://doi.org/10.5194/se-10-117-2019, 2019〈br〉 The Caledonian mountains formed when Baltica and Laurentia collided around 450–400 million years ago. This work describes the history of the rocks and the dynamics of that continental collision through space and time using field mapping, estimated pressures and temperatures, and age dating on rocks from northern Norway. The rocks preserve continental collision between 440–430 million years ago, and an unusual pressure–temperature evolution suggests unusual tectonic activity prior to collision.

Beschreibung: 〈b〉Correlation between tectonic stress regimes and methane seepage on the western Svalbard margin〈/b〉〈br〉 Andreia Plaza-Faverola and Marie Keiding〈br〉 Solid Earth, 10, 79-94, https://doi.org/10.5194/se-10-79-2019, 2019〈br〉 Vast amounts of methane are released to the oceans at continental margins (seepage). The mechanisms controlling when and how much methane is released are not fully understood. In the Fram Strait seepage may be affected by complex tectonic processes. We modelled the stress generated on the sediments exclusively due to the opening of the mid-ocean ridges and found that changes in the stress field may be controlling when and where seepage occurs, which has implications for seepage reconstruction.

Beschreibung: 〈b〉Mechanisms of destructing translational domains in passive margin salt basins: Insights from analogue modelling〈/b〉〈br〉 Zhiyuan Ge, Matthias Rosenau, Michael Warsitzka, and Rob L. Gawthorpe〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2019-2,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Salt basins are important as they bear abundant hydrocarbon resource and record the geological evolution. However, current understanding does not fully reconcile with natural examples. Using state-of-the-art analogue modelling technique, we study how an undefromed area occurs in the experiment and gets destroyed later. The results suggest the natural systems work quite differently as we currently know. This study can help us to better explore natural resources in the salt basins.

Beschreibung: 〈b〉The imprints of contemporary mass redistribution on regional sea level and vertical land motion observations〈/b〉〈br〉 Thomas Frederikse, Felix W. Landerer, and Lambert Caron〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-128,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Due to ice sheets and glaciers losing mass, and because continents get wetter and drier, a lot of water is redistributed over the earth's surface. The earth is not completely rigid, but deforms under these changes in the load on top. This deformation affects sea-level observations. With the GRACE satellite mission, we can measure this redistribution of water, and compute the resulting deformation. We use this computed deformation to improve the accuracy of sea-level observations.

Beschreibung: 〈b〉The impact of earthquake cycle variability on neotectonic and paleoseismic slip rate estimates〈/b〉〈br〉 Richard Styron〈br〉 Solid Earth, 10, 15-25, https://doi.org/10.5194/se-10-15-2019, 2019〈br〉 Successive earthquakes on a single fault are not perfectly periodic in time. There is some natural random variability. This leads to variations in estimated fault slip rates over short timescales though the longer-term mean slip rate stays constant, which may cause problems when comparing slip rates at different timescales. This paper is the first to quantify these effects, demonstrating substantial variation in slip rates over a few to tens of earthquakes, but much less at longer timescales.

Beschreibung: 〈b〉How do we see fractures? Quantifying subjective bias in fracture data collection〈/b〉〈br〉 Billy J. Andrews, Jennifer J. Roberts, Zoe K. Shipton, Sabina Bigi, Maria C. Tartarello, and Gareth O. Johnson〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-135,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 Rocks often contain fracture networks, which can strongly impact sub-surface fluid flow and the strength of a rock mass. We examine how participants interpret the same fracture network, both in the field and using field photographs. Considerable variability between participant's resulted in significant differences in derived fracture statistics, which are often used as inputs for geological models. We suggest protocols to recognise, understand and limit this effect on fracture data collection.

Beschreibung: 〈b〉High-precision U–Pb ages in the early Tithonian to early Berriasian and implications for the numerical age of the Jurassic–Cretaceous boundary〈/b〉〈br〉 Luis Lena, Rafael López-Martínez, Marina Lescano, Beatriz Aguire-Urreta, Andrea Concheyro, Verónica Vennari, Maximiliano Naipauer, Elias Samankassou, Márcio Pimentel, Victor A. Ramos, and Urs Schaltegger〈br〉 Solid Earth, 10, 1-14, https://doi.org/10.5194/se-10-1-2019, 2019〈br〉 This paper investigates the numerical age of the J–K boundary that remains one of the last main Phanerozoic system boundaries without an adequate constraint by adequate radioisotopic ages. Here we find that there is potentially 4 Myr of difference between the current age of the J–K boundary and our data.

Beschreibung: Much effort is being made to extract the dynamic components of the Earth's topography driven by density heterogeneities in the mantle. Seismically mapped density anomalies have been used as an input into mantle convection models to predict the present-day mantle flow and stresses applied on the Earth's surface, resulting in dynamic topography. However, mantle convection models give dynamic topography amplitudes generally larger by a factor of ∼2, depending on the flow wavelength, compared to dynamic topography amplitudes obtained by removing the isostatically compensated topography from the Earth's topography. In this paper, we use 3-D numerical experiments to evaluate the extent to which the dynamic topography depends on mantle rheology. We calculate the amplitude of instantaneous dynamic topography induced by the motion of a small spherical density anomaly (∼100 km radius) embedded into the mantle. Our experiments show that, at relatively short wavelengths (

Beschreibung: Geothermal energy is an important and sustainable resource that has more potential than is currently utilized. Whether or not a deep geothermal resource can be exploited, mostly depends on, besides temperature, the utilizable reservoir volume over time, which in turn largely depends on petrophysical parameters. We show, using over 1000 (n=1027) 4-D finite-element models of a simple geothermal doublet, that the lifetime of a reservoir is a complex function of its geological parameters, their heterogeneity, and the background hydraulic gradient (BHG). In our models, we test the effects of porosity, permeability, and BHG in an isotropic medium. Furthermore, we simulate the effect of permeability contrast and anisotropy induced by layering, fractures, and a fault. We quantify the lifetime of the reservoir by measuring the time to thermal breakthrough, i.e. how many years pass before the temperature of the produced fluid falls below the 100 ∘C threshold. The results of our sensitivity study attest to the positive effect of high porosity; however, high permeability and BHG can combine to outperform the former. Particular configurations of all the parameters can cause either early thermal breakthrough or extreme longevity of the reservoir. For example, the presence of high-permeability fractures, e.g. in a fault damage zone, can provide initially high yields, but it channels fluid flow and therefore dramatically restricts the exploitable reservoir volume. We demonstrate that the magnitude and orientation of the BHG, provided permeability is sufficiently high, are the prime parameters that affect the lifetime of a reservoir. Our numerical experiments show also that BHGs (low and high) can be outperformed by comparatively small variations in permeability contrast (103) and fracture-induced permeability anisotropy (101) that thus strongly affect the performance of geothermal reservoirs.

Beschreibung: Representing fractures explicitly using a discrete fracture network (DFN) approach is often necessary to model the complex physics that govern thermo-hydro-mechanical–chemical processes (THMC) in porous media. DFNs find applications in modelling geothermal heat recovery, hydrocarbon exploitation, and groundwater flow. It is advantageous to construct DFNs from the photogrammetry of fractured outcrop analogues as the DFNs would capture realistic, fracture network properties. Recent advances in drone photogrammetry have greatly simplified the process of acquiring outcrop images, and there is a remarkable increase in the volume of image data that can be routinely generated. However, manually digitizing fracture traces is time-consuming and inevitably subject to interpreter bias. Additionally, variations in interpretation style can result in different fracture network geometries, which, may then influence modelling results depending on the use case of the fracture study. In this paper, an automated fracture trace detection technique is introduced. The method consists of ridge detection using the complex shearlet transform coupled with post-processing algorithms that threshold, skeletonize, and vectorize fracture traces. The technique is applied to the task of automatic trace extraction at varying scales of rock discontinuities, ranging from 100 to 102 m. We present automatic trace extraction results from three different fractured outcrop settings. The results indicate that the automated approach enables the extraction of fracture patterns at a volume beyond what is manually feasible. Comparative analysis of automatically extracted results with manual interpretations demonstrates that the method can eliminate the subjectivity that is typically associated with manual interpretation. The proposed method augments the process of characterizing rock fractures from outcrops.

Beschreibung: Deformation microstructures of albitic plagioclase and K-feldspar were investigated in mylonitic pegmatites from the Austroalpine basement south of the western Tauern Window by polarized light microscopy, electron microscopy and electron backscatter diffraction to evaluate feldspar deformation mechanisms at greenschist facies conditions. The main mylonitic characteristics are alternating almost monophase quartz and albite layers, surrounding porphyroclasts of deformed feldspar and tourmaline. The dominant deformation microstructures of K-feldspar porphyroclasts are intragranular fractures at a high angle to the stretching lineation. The fractures are healed or sealed by polyphase aggregates of albite, K-feldspar, quartz and mica, which also occur along intragranular fractures of tourmaline and strain shadows around other porphyroclasts. These polyphase aggregates indicate dissolution–precipitation creep. K-feldspar porphyroclasts are partly replaced by albite characterized by a cuspate interface. This replacement is interpreted to take place by interface-coupled dissolution–precipitation driven by a solubility difference between K-feldspar and albite. Albite porphyroclasts are replaced at boundaries parallel to the foliation by fine-grained monophase albite aggregates of small strain-free new grains mixed with deformed fragments. Dislocation glide is indicated by bent and twinned albite porphyroclasts with internal misorientation. An indication of effective dislocation climb with dynamic recovery, for example, by the presence of subgrains, is systematically missing. We interpret the grain size reduction of albite to be the result of coupled dislocation glide and fracturing (low-temperature plasticity). Subsequent growth is by a combination of strain-induced grain boundary migration and formation of growth rims, resulting in an aspect ratio of albite with the long axis within the foliation. This strain-induced replacement by nucleation (associated dislocation glide and microfracturing) and subsequent growth is suggested to result in the observed monophase albite layers, probably together with granular flow. The associated quartz layers show characteristics of dislocation creep by the presence of subgrains, undulatory extinction and sutured grain boundaries. We identified two endmember matrix microstructures: (i) alternating layers of a few hundred micrometres' width, with isometric, fine-grained feldspar (on average 15 µm in diameter) and coarse-grained quartz (a few hundred micrometres in diameter), representing lower strain compared to (ii) alternating thin layers of some tens of micrometres' width composed of fine-grained quartz (

Beschreibung: On 3 September 2017 official channels of the Democratic People's Republic of Korea announced the successful test of a thermonuclear device. Only seconds to minutes after the alleged nuclear explosion at the Punggye-ri nuclear test site in the mountainous region in the country's northeast at 03:30:02 (UTC), hundreds of seismic stations distributed all around the globe picked up strong and distinct signals associated with an explosion. Different seismological agencies reported body wave magnitudes of well above 6.0, consequently estimating the explosive yield of the device on the order of hundreds of kT TNT equivalent. The 2017 event can therefore be assessed as being multiple times larger in energy than the two preceding North Korean events in January and September 2016. This study provides a multi-technology analysis of the 2017 North Korean event and its aftermath using a wide array of geophysical methods. Seismological investigations locate the event within the test site at a depth of approximately 0.6 km below the surface. The radiation and generation of P- and S-wave energy in the source region are significantly influenced by the topography of the Mt. Mantap massif. Inversions for the full moment tensor of the main event reveal a dominant isotropic component accompanied by significant amounts of double couple and compensated linear vector dipole terms, confirming the explosive character of the event. The analysis of the source mechanism of an aftershock that occurred around 8 min after the test in the direct vicinity suggest a cavity collapse. Measurements at seismic stations of the International Monitoring System result in a body wave magnitude of 6.2, which translates to an yield estimate of around 400 kT TNT equivalent. The explosive yield is possibly overestimated, since topography and depth phases both tend to enhance the peak amplitudes of teleseismic P waves. Interferometric synthetic aperture radar analysis using data from the ALOS-2 satellite reveal strong surface deformations in the epicenter region. Additional multispectral optical data from the Pleiades satellite show clear landslide activity at the test site. The strong surface deformations generated large acoustic pressure peaks, which were observed as infrasound signals with distinctive waveforms even at distances of 401 km. In the aftermath of the 2017 event, atmospheric traces of the fission product 133Xe were detected at various locations in the wider region. While for 133Xe measurements in September 2017, the Punggye-ri test site is disfavored as a source by means of atmospheric transport modeling, detections in October 2017 at the International Monitoring System station RN58 in Russia indicate a potential delayed leakage of 133Xe at the test site from the 2017 North Korean nuclear test.

Beschreibung: The numerical age of the Jurassic–Cretaceous boundary has been controversial and difficult to determine. In this study, we present high-precision U–Pb geochronological data around the Jurassic–Cretaceous boundary in two distinct sections from different sedimentary basins: the Las Loicas, Neuquén Basin, Argentina, and the Mazatepec, Sierra Madre Oriental, Mexico. These two sections contain primary and secondary fossiliferous markers for the boundary as well as interbedded volcanic ash horizons, allowing researchers to obtain new radioisotopic dates in the late Tithonian and early Berriasian. We also present the first age determinations in the early Tithonian and tentatively propose a minimum duration for the stage as a cross-check for our ages in the early Berriasian. Given our radioisotopic ages in the early Tithonian to early Berriasian, we discuss implications for the numerical age of the boundary.

Beschreibung: E-twinning is a common plastic deformation mechanism in calcite deformed at low temperature. Strain rate, temperature and confining pressure have negligible effects on twinning activation which is mainly dependent on differential stress. The critical resolved shear stress (CRSS) required for twinning activation is dependent on grain size and strain hardening. This CRSS value may obey the Hall–Petch relation, but due to sparse experimental data its actual evolution with grain size and strain still remains a matter of debate. In order to provide additional constraints on twinning activation and development, new mechanical tests were carried out at room temperature on unconfined single crystals of calcite, with different sizes and crystallographic orientations. Uniaxial deformation was performed at a controlled displacement rate, while the sample surface was monitored using optical microscopy and a high-resolution CCD (charge-coupled device) camera. The retrieved macroscopic stress–strain behavior of the crystals was correlated with the surface observations of the deformation process. Results show (1) the onset of crystal plasticity with the activation of the first isolated mechanical twins during the strain hardening stage, and (2) the densification and thickening of twin lamellae during the steady-state flow stress stage. Such thickening of twin lamellae at room temperature emphasizes that calcite twin morphology is not controlled solely by temperature. The different values for the CRSS obtained for the activation of isolated twins and for the onset of twin densification and thickening raises questions regarding the appropriate value to be considered when using calcite twin data for stress inversion purposes.

Beschreibung: A terrestrial reference frame (TRF) is a basis for precise orbit determination of Earth-orbiting satellites, since it defines positions and velocities of stations, the tracking data of which are used to derive satellite positions. In this paper, we investigate the impact of the International Terrestrial Reference Frame realization ITRF2014, as compared to its predecessor ITRF2008, on the quality of orbits, namely, on root-mean-square (rms) fits of observations and orbital arc overlaps of three altimetry satellites (TOPEX/Poseidon, Jason-1, and Jason-2) in the time interval from August 1992 to April 2015 and on altimetry products computed using these orbits, such as single-satellite altimeter crossover differences, radial and geographically correlated mean sea surface height (SSH) errors and regional and global mean sea level trends. The satellite orbits are computed using satellite laser ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) observations of a global network of stations. We have found that using ITRF2014 generally improves the orbit quality as compared to using ITRF2008. Thus, the mean values of the rms fits of SLR observations decreased (improved) by 2.4 % and 8.8 % for Jason-1 and Jason-2, respectively, but are almost not impacted for TOPEX/Poseidon when using ITRF2014 instead of ITRF2008. The internal orbit consistency in the radial direction (as derived from arc overlaps) is reduced (improved) by 6.6 %, 2.3 %, and 5.9 % for TOPEX/Poseidon, Jason-1, and Jason-2, respectively. Single-satellite altimetry crossover analyses indicate reduction (improvement) in the absolute mean crossover differences by 0.2 mm (8.1 %) for TOPEX, 0.4 mm (17.7 %) for Jason-1, and 0.6 mm (30.9 %) for Jason-2 with ITRF2014 instead of ITRF2008. The major improvement of the mean values of the rms of crossover differences (0.13 mm; 0.3 %) has been found for Jason-2. Multi-mission crossover analysis shows slight improvements in the standard deviations of radial errors: 0.1 %, 0.2 %, and 1.6 % for TOPEX, Jason-1, and Jason-2, respectively. The standard deviations of geographically correlated mean SSH errors improved by 1.1 % for Jason-1 and 5.4 % for Jason-2 and degraded by 1.3 % for TOPEX. The change from ITRF2008 to ITRF2014 orbits only has minor effects on the estimation of regional and global sea level trends over the 22-year time series from 1993 to 2015. However, on interannual timescales (3–8 years) large-scale coherent trend patterns are observed that seem to be connected to drifts between the origins of the tracking station networks. This leads to the changes in interannual global mean sea level of up to 0.06 mm yr−1 for TOPEX, 0.05 mm yr−1 for Jason-1, and up to 0.12 mm yr−1 for Jason-2, i.e., up to 4 % of the corresponding sea level signal based on altimetry for timescales of 3 to 8 years. The respective changes in the regional sea level trend on these timescales are up to 0.4 mm yr−1 in the time span from April 1993 to July 2008 and up to 1.0 mm yr−1 in the time span from July 2008 to April 2015.

Beschreibung: Recent seismological observations focusing on the collapse of an impulsive wavelet revealed the existence of small-scale random heterogeneities in the earth medium. The radiative transfer theory (RTT) is often used for the study of the propagation and scattering of wavelet intensities, the mean square amplitude envelopes through random media. For the statistical characterization of the power spectral density function (PSDF) of the random fractional fluctuation of velocity inhomogeneities in a 3-D space, we use an isotropic von Kármán-type function characterized by three parameters: the root mean square (RMS) fractional velocity fluctuation, the characteristic length, and the order of the modified Bessel function of the second kind, which leads to the power-law decay of the PSDF at wavenumbers higher than the corner. We compile reported statistical parameters of the lithosphere and the mantle based on various types of measurements for a wide range of wavenumbers: photo-scan data of rock samples; acoustic well-log data; and envelope analyses of cross-hole experiment seismograms, regional seismograms, and teleseismic waves based on the RTT. Reported exponents of wavenumber are distributed between −3 and −4, where many of them are close to −3. Reported RMS fractional fluctuations are on the order of 0.01–0.1 in the crust and the upper mantle. Reported characteristic lengths distribute very widely; however, each one seems to be restricted by the dimension of the measurement system or the sample length. In order to grasp the spectral characteristics, eliminating strong heterogeneity data and the lower mantle data, we have plotted all the reported PSDFs of the crust and the upper mantle against wavenumber for a wide range (10−3–108 km−1). We find that the spectral envelope of those PSDFs is well approximated by the inverse cube of wavenumber. It suggests that the earth-medium randomness has a broad spectrum. In theory, we need to re-examine the applicable range of the Born approximation in the RTT when the wavenumber of a wavelet is much higher than the corner. In observation, we will have to carefully measure the PSDF on both sides of the corner. We may consider the obtained power-law decay spectral envelope as a reference for studying the regional differences. It is interesting to study what kinds of geophysical processes created the observed power-law spectral envelope at different scales and in different geological environments in the solid earth medium.

Beschreibung: We use observations of surface waves in the ambient noise field recorded at a dense seismic array to image the North Anatolian Fault zone (NAFZ) in the region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike-slip fault system extending ∼1200 km across northern Turkey that poses a high level of seismic hazard, particularly to the city of Istanbul. We obtain maps of phase velocity variation using surface wave tomography applied to Rayleigh and Love waves and construct high-resolution images of S-wave velocity in the upper 10 km of a 70 × 30 km region around Lake Sapanca. We observe low S-wave velocities (3.2 km s−1) associated with a shallow crystalline basement. We measure azimuthal anisotropy in our phase velocity observations, with the fast direction seeming to align with the strike of the fault at periods shorter than 4 s. At longer periods up to 10 s, the fast direction aligns with the direction of maximum extension for the region (∼45∘). The signatures of both the northern and southern branches of the NAFZ are clearly associated with strong gradients in seismic velocity that also denote the boundaries of major tectonic units. Our results support the conclusion that the development of the NAFZ has exploited this pre-existing contrast in physical properties.

Beschreibung: The nature of the Ionian Sea crust has been the subject of scientific debate for more than 30 years, mainly because seismic imaging of the deep crust and upper mantle of the Ionian Abyssal Plain (IAP) has not been conclusive to date. The IAP is sandwiched between the Calabrian and Hellenic subduction zones in the central Mediterranean. A NNE–SSW-oriented 131 km long seismic refraction and wide-angle reflection profile, consisting of eight ocean bottom seismometers and hydrophones, was acquired in 2014. The profile was designed to univocally confirm the proposed oceanic nature of the IAP crust as a remnant of the Tethys and to confute its interpretation as a strongly thinned part of the African continental crust. A P-wave velocity model developed from travel-time forward modelling is refined by gravimetric data and synthetic modelling of the seismic data. A roughly 6–7 km thick crust with velocities ranging from 5.1 to 7.2 km s−1, top to bottom, can be traced throughout the IAP. In the vicinity of the Medina seamounts at the southern IAP boundary, the crust thickens to about 9 km and seismic velocities decrease to 6.8 km s−1 at the crust–mantle boundary. The seismic velocity distribution and depth of the crust–mantle boundary in the IAP document its oceanic nature and support the interpretation of the IAP as a remnant of the Tethys lithosphere with the Malta Escarpment as a transform margin and a Tethys opening in the NNW–SSE direction.

Beschreibung: New field work, combined with analysis of high-resolution aerial photographs, digital elevation models, and satellite imagery, has identified an active fault that is traceable for ∼90 km across the Seymchan Basin and is part of the Ulakhan fault system, which is believed to form the Okhotsk–North America plate boundary. Age dating of alluvial fan sediments in a channel system that is disturbed by fault activity suggests the current scarp is a result of a series of large earthquakes (≥Mw 7.5) that have occurred since 11.6±2.7 ka. A possible channel feature offset by 62±4 m associated with these sediments yields a slip rate of 5.3±1.3 mm yr−1, in broad agreement with rates suggested from global plate tectonics. Our results clearly identify the Ulakhan fault as the Okhotsk–North America plate boundary and show that tectonic strain release is strongly concentrated on the boundaries of Okhotsk. In light of our results, the likelihood of recurrence of Mw 7.5 earthquakes is high, suggesting a previously underestimated seismic hazard across the region.

Beschreibung: In the European region, the magnetic field at satellite altitudes (∼350 km) is mainly defined by a long-wavelength magnetic low, called the Central European Magnetic Low (CEML) here, located to the southwest of the Trans-European Suture Zone (TESZ). We studied this area through a joint analysis of magnetic and total gradient (∇T) anomaly maps for a range of different altitudes of 5, 100 and 350 km. Tests on synthetic models showed the usefulness of the joint analysis at various altitudes to identify reverse dipolar anomalies and to characterize areas in which magnetization is weak. This way we identified areas where either reversely or normally magnetized sources are locally dominant. At a European scale these anomalies are sparse, with a low degree of coalescence effect. The ∇T map indeed presents generally small values within the CEML area, indicating that the Paleozoic Platform is weakly magnetized. At 350 km of altitude, the TESZ effect is largely dominant: with intense ∇T highs above the East European Craton (EEC) and very small values above the Paleozoic Platform, this again denotes a weakly magnetized crust. Small coalescence effects are masked by the trend of the TESZ. Although we identified sparsely located reversely magnetized sources in the Paleozoic Platform of the CEML, the joint analysis does not support a model of a generally reversely magnetized crust. Instead, our analysis strongly favors the hypothesis that the CEML anomaly is mainly caused by a sharp contrast between the magnetic properties of the EEC and Paleozoic Platform.

Beschreibung: Long-term measurements of volcanic gas emissions conducted during the last decade suggest that under certain conditions the magnitude or chemical composition of volcanic emissions exhibits periodic variations with a period of about 2 weeks. A possible cause of such a periodicity can be attributed to the Earth tidal potential. The phenomenology of such a link has been debated for long, but no quantitative model has yet been proposed. The aim of this paper is to elucidate whether a causal link between tidal forcing and variations in volcanic degassing can be traced analytically. We model the response of a simplified magmatic system to the local tidal gravity variations and derive a periodical vertical magma displacement in the conduit with an amplitude of 0.1–1 m, depending on the geometry and physical state of the magmatic system. We find that while the tide-induced vertical magma displacement presumably has no significant direct effect on the volatile solubility, the differential magma flow across the radial conduit profile may result in a significant increase in the bubble coalescence rate at a depth of several kilometres by up to several multiples of 10 %. Because bubble coalescence facilitates separation of gas from magma and thus enhances volatile degassing, we argue that the derived tidal variation may propagate to a manifestation of varying volcanic degassing behaviour. The presented model provides a first basic framework which establishes an analytical understanding of the link between the Earth tides and volcanic degassing.

Beschreibung: Few data exist that provide insight into processes affecting the long-term carbon cycle at shallow forearc depths. To better understand the mobilization of C in sediments and crust of the subducting slab, we investigated carbonate materials that originate from the subduction channel at the Mariana forearc (

Beschreibung: The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African–Adriatic plates in the Mediterranean. This area is seismically active with instrumentally and/or historically recorded Mw〉7.0 earthquakes, and it is affected by recently discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently discovered one (called the Bortoluzzi Mud Volcano or BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). High-resolution bathymetric backscatter surveys, seismic reflection profiles, geochemical and earthquake data, and a gravity core are used here to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ≃22 m high and ≃1100 m in diameter with steep slopes (up to a dip of 22∘). It sits atop the Calabrian accretionary wedge and a system of flower-like oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustal-derived fluids similar to the fluids collected from a mud volcano located on the Calabria mainland over the same accretionary wedge. These results attest to the occurrence of open crustal pathways for fluids through the BMV down to at least the Messinian evaporites at about −3000 m. This evidence is also substantiated by helium isotope ratios and by comparison and contrast with different geochemical data from three seawater columns located over other active faults in the Ionian Sea area. One conclusion is that the BMV may be useful for tracking the seismic cycle of active faults through geochemical monitoring. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study contributes to indicating a future path for the use of mud volcanoes in the monitoring and mitigation of natural hazards.

Beschreibung: Geologic carbon storage, as well as other geo-energy applications, such as geothermal energy, seasonal natural gas storage and subsurface energy storage imply fluid injection and/or extraction that causes changes in rock stress field and may induce (micro)seismicity. If felt, seismicity has a negative effect on public perception and may jeopardize wellbore stability and damage infrastructure. Thus, induced earthquakes should be minimized to successfully deploy geo-energies. However, numerous processes may trigger induced seismicity, which contribute to making it complex and translates into a limited forecast ability of current predictive models. We review the triggering mechanisms of induced seismicity. Specifically, we analyze (1) the impact of pore pressure evolution and the effect that properties of the injected fluid have on fracture and/or fault stability; (2) non-isothermal effects caused by the fact that the injected fluid usually reaches the injection formation at a lower temperature than that of the rock, inducing rock contraction, thermal stress reduction and stress redistribution around the cooled region; (3) local stress changes induced when low-permeability faults cross the injection formation, which may reduce their stability and eventually cause fault reactivation; (4) stress transfer caused by seismic or aseismic slip; and (5) geochemical effects, which may be especially relevant in carbonate-containing formations. We also review characterization techniques developed by the authors to reduce the uncertainty in rock properties and subsurface heterogeneity both for the screening of injection sites and for the operation of projects. Based on the review, we propose a methodology based on proper site characterization, monitoring and pressure management to minimize induced seismicity.

Beschreibung: We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q−1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high-frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wave-field seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to northwest Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp

Beschreibung: Not all continental rifts mature to form a young ocean. The mechanism and duration of their cessation depend on the crustal structure, modifications in plate kinematics, lithospheric thermal response, or the intensity of subcrustal flow (e.g., plume activity). The cessation is recorded in the structure and stratigraphy of the basins that develop during the rifting process. This architecture is lost due to younger tectonic inversion, severe erosion, or even burial into greater depths that forces their detection by low-resolution geophysical imaging. The current study focuses on a uniquely preserved Oligo-Miocene rift that was subsequently taken over by a crossing transform fault system and, mostly due to that, died out. We integrate all geological, geophysical, and previous study results from across the southern Galilee to unravel the structural development of the Irbid failing rift in northwest Arabia. Despite tectonic, magmatic, and geomorphologic activity postdating the rifting, its subsurface structure northwest of the Dead Sea fault is preserved at depths of up to 1 km. Our results show that a series of basins subsided at the rift front, i.e., rift termination, across the southern Galilee. We constrain the timing and extent of their subsidence into two main stages based on facies analysis and chronology of magmatism. Between 20 and 9 Ma grabens and half-grabens subsided within a larger releasing jog, following a NW direction of a deeper presumed principal displacement zone. The basins continued to subside until a transition from the transtensional Red Sea to the transpressional Dead Sea stress regime occurred. With the transition, the basins ceased to subside as a rift, while the Dead Sea fault split the jog structure. Between 9 and 5 Ma basin subsidence accentuated and an uplift of their margins accompanied their overall elongation to the NNE. Our study provides for the first time a structural as well as tectonic context for the southern Galilee basins. Based on this case study we suggest that the rift did not fail but rather faded and was taken over by a more dominant stress regime. Otherwise, these basins of a failing rift could have simply died out peacefully.

Beschreibung: We use two-dimensional thermomechanical models to investigate the potential role of rapid filling of foreland basins in the development of orogenic foreland fold-and-thrust belts. We focus on the extensively studied example of the Western European Alps, where a sudden increase in foreland sedimentation rate during the mid-Oligocene is well documented. Our model results indicate that such an increase in sedimentation rate will temporarily disrupt the formation of an otherwise regular, outward-propagating basement thrust-sheet sequence. The frontal basement thrust active at the time of a sudden increase in sedimentation rate remains active for a longer time and accommodates more shortening than the previous thrusts. As the propagation of deformation into the foreland fold-and-thrust belt is strongly connected to basement deformation, this transient phase appears as a period of slow migration of the distal edge of foreland deformation. The predicted pattern of foreland-basin and basement thrust-front propagation is strikingly similar to that observed in the North Alpine Foreland Basin and provides an explanation for the coeval mid-Oligocene filling of the Swiss Molasse Basin, due to increased sediment input from the Alpine orogen, and a marked decrease in thrust-front propagation rate. We also compare our results to predictions from critical-taper theory, and we conclude that they are broadly consistent even though critical-taper theory cannot be used to predict the timing and location of the formation of new basement thrusts when sedimentation is included. The evolution scenario explored here is common in orogenic foreland basins; hence, our results have broad implications for orogenic belts other than the Western Alps.

Beschreibung: The propagation of a seismic rupture on a fault introduces spatial variations in the seismic wave field surrounding the fault. This directivity effect results in larger shaking amplitudes in the rupture propagation direction. Its seismic radiation pattern also causes amplitude variations between the strike-normal and strike-parallel components of horizontal ground motion. We investigated the landslide response to these effects during the 2016 Kumamoto earthquake (Mw 7.1) in central Kyushu (Japan). Although the distribution of some 1500 earthquake-triggered landslides as a function of rupture distance is consistent with the observed Arias intensity, the landslides were more concentrated to the northeast of the southwest–northeast striking rupture. We examined several landslide susceptibility factors: hillslope inclination, the median amplification factor (MAF) of ground shaking, lithology, land cover, and topographic wetness. None of these factors sufficiently explains the landslide distribution or orientation (aspect), although the landslide head scarps have an elevated hillslope inclination and MAF. We propose a new physics-based ground-motion model (GMM) that accounts for the seismic rupture effects, and we demonstrate that the low-frequency seismic radiation pattern is consistent with the overall landslide distribution. Its spatial pattern is influenced by the rupture directivity effect, whereas landslide aspect is influenced by amplitude variations between the fault-normal and fault-parallel motion at frequencies

Beschreibung: Understanding the development of post-glacial faults and their associated seismic activity is crucial for risk assessment in Scandinavia. However, imaging these features and their geological environment is complicated due to special challenges of their hardrock setting, such as weak impedance contrasts, often high noise levels and crooked acquisition lines. A crooked-line geometry can cause time shifts that seriously de-focus and deform reflections containing a cross-dip component. Advanced processing methods like swath 3-D processing and 3-D pre-stack migration can, in principle, handle the crooked-line geometry but may fail when the noise level is too high. For these cases, the effects of reflector cross-dip can be compensated for by introducing a linear correction term into the standard processing flow. However, existing implementations of the cross-dip correction rely on a slant stack approach which can, for some geometries, lead to a duplication of reflections. Here, we present a module for the cross-dip correction that avoids the reflection duplication problem by shifting the reflections prior to stacking. Based on tests with synthetic data, we developed an iterative processing scheme where a sequence consisting of cross-dip correction, velocity analysis and dip-moveout (DMO) correction is repeated until the stacked image converges. Using our new module to reprocess a reflection seismic profile over the post-glacial Burträsk fault in northern Sweden increased the image quality significantly. Strike and dip information extracted from the cross-dip analysis helped to interpret a set of southeast-dipping reflections as shear zones belonging to the regional-scale Burträsk Shear Zone (BSZ), implying that the BSZ itself is not a vertical but a southeast-dipping feature. Our results demonstrate that the cross-dip correction is a highly useful alternative to more sophisticated processing methods for noisy datasets. This highlights the often underestimated potential of rather simple but noise-tolerant methods in processing hardrock seismic data.

Beschreibung: The Mountain Front Flexure marks a dominant topographic step in the frontal part of the Zagros Fold–Thrust Belt. It is characterized by numerous active anticlines atop of a basement fault. So far, little is known about the relative activity of the anticlines, about their evolution, or about how crustal deformation migrates over time. We assessed the relative landscape maturity of three along-strike anticlines (from SE to NW: Harir, Perat, and Akre) located on the hanging wall of the Mountain Front Flexure in the Kurdistan Region of Iraq to identify the most active structures and to gain insights into the evolution of the fold–thrust belt. Landscape maturity was evaluated using geomorphic indices such as hypsometric curves, hypsometric integral, surface roughness, and surface index. Subsequently, numerical landscape evolution models were run to estimate the relative time difference between the onset of growth of the anticlines, using the present-day topography of the Harir Anticline as a base model. A stream power equation was used to introduce fluvial erosion, and a hillslope diffusion equation was applied to account for colluvial sediment transport. For different time steps of model evolution, we calculated the geomorphic indices generated from the base model. While Akre Anticline shows deeply incised valleys and advanced erosion, Harir and Perat anticlines have relatively smoother surfaces and are supposedly younger than the Akre Anticline. The landscape maturity level decreases from NW to SE. A comparison of the geomorphic indices of the model output to those of the present-day topography of Perat and Akre anticlines revealed that it would take the Harir Anticline about 80–100 and 160–200 kyr to reach the maturity level of the Perat and Akre anticlines, respectively, assuming erosion under constant conditions and constant rock uplift rates along the three anticlines. Since the factors controlling geomorphology (lithology, structural setting, and climate) are similar for all three anticlines, and under the assumption of constant growth and erosion conditions, we infer that uplift of the Akre Anticline started 160–200 kyr before that of the Harir Anticline, with the Perat Anticline showing an intermediate age. A NW-ward propagation of the Harir Anticline itself implies that the uplift has been independent within different segments. Our method of estimating the relative age difference can be applied to many other anticlines in the Mountain Front Flexure region to construct a model of temporal evolution of this belt.

Beschreibung: The Sea of Marmara, in northwestern Turkey, is a transition zone where the dextral North Anatolian Fault zone (NAFZ) propagates westward from the Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context of seismic hazard of Istanbul, a metropolitan area with about 15 million inhabitants. Geophysical observations indicate that the crust is heterogeneous beneath the Marmara basin, but a detailed characterization of the crustal heterogeneities is still missing. To assess if and how crustal heterogeneities are related to the NAFZ segmentation below the Sea of Marmara, we develop new crustal-scale 3-D density models which integrate geological and seismological data and that are additionally constrained by 3-D gravity modeling. For the latter, we use two different gravity datasets including global satellite data and local marine gravity observation. Considering the two different datasets and the general non-uniqueness in potential field modeling, we suggest three possible “end-member” solutions that are all consistent with the observed gravity field and illustrate the spectrum of possible solutions. These models indicate that the observed gravitational anomalies originate from significant density heterogeneities within the crust. Two layers of sediments, one syn-kinematic and one pre-kinematic with respect to the Sea of Marmara formation are underlain by a heterogeneous crystalline crust. A felsic upper crystalline crust (average density of 2720 kg m−3) and an intermediate to mafic lower crystalline crust (average density of 2890 kg m−3) appear to be cross-cut by two large, dome-shaped mafic high-density bodies (density of 2890 to 3150 kg m−3) of considerable thickness above a rather uniform lithospheric mantle (3300 kg m−3). The spatial correlation between two major bends of the main Marmara fault and the location of the high-density bodies suggests that the distribution of lithological heterogeneities within the crust controls the rheological behavior along the NAFZ and, consequently, maybe influences fault segmentation and thus the seismic hazard assessment in the region.

Beschreibung: The dynamic evolution of fault zones at the seismogenic brittle–ductile transition zone (BDTZ) expresses the delicate interplay between numerous physical and chemical processes. Deformation and fluid flow at the BDTZ are closely related and mutually dependent during repeating and transient cycles of frictional and viscous deformation. Despite numerous studies documenting in detail seismogenic faults exhumed from the BDTZ, uncertainties remain as to the exact role of fluids in facilitating broadly coeval brittle and ductile deformation at that structural level. We combine structural analysis, fluid inclusion, and mineral chemistry data from synkinematic and authigenic minerals to reconstruct the temporal variations in fluid pressure (Pf), temperature (T), and bulk composition (X) of the fluids that mediated deformation and steered strain localization along BFZ300, a strike–slip fault originally active at the BDTZ. BFZ300 deforms the Paleoproterozoic migmatitic basement of southwestern Finland and hosts in its core two laterally continuous quartz veins formed by two texturally distinct types of quartz – Qtz I and Qtz II, with Qtz I older than Qtz II. Veins within the damage zone are formed exclusively by Qtz I. Mesostructural and microstructural analysis combined with fluid compositional data indicate recurrent cycles of mutually overprinting brittle and ductile deformation triggered by oscillations of fluid pressure peaking at 210 MPa. Fluid inclusion microthermometry and mineral pair geothermometry indicate that the two documented quartz types precipitated from different fluid batches, with bulk salinities in the 1 wt % NaCleq–5 wt % NaCleq range for Qtz I and in the 6 wt % NaCleq–11 wt % NaCleq range for Qtz II. The temperature of the fluids involved with initial strain localization and later fault reactivation evolved through time from 〉 350 ∘C during Qtz I precipitation to

Beschreibung: Imaging via pre-stack depth migration (PSDM) of reflection towed-streamer multichannel seismic (MCS) data at the scale of the whole crust is inherently difficult. This is because the depth penetration of the seismic wavefield is controlled, firstly, by the acquisition design, such as streamer length and air-gun source configuration, and secondly by the complexity of the crustal structure. Indeed, the limited length of the streamer makes the estimation of velocities from deep targets challenging due to the velocity–depth ambiguity. This problem is even more pronounced when processing 2-D seismic data due to the lack of multi-azimuthal coverage. Therefore, in order to broaden our knowledge about the deep crust using seismic methods, we present the development of specific imaging workflows that integrate different seismic data. Here we propose the combination of velocity model building using (i) first-arrival tomography (FAT) and full-waveform inversion (FWI) of wide-angle, long-offset data collected by stationary ocean-bottom seismometers (OBSs) and (ii) PSDM of short-spread towed-streamer MCS data for reflectivity imaging, with the former velocity model as a background model. We present an application of such a workflow to seismic data collected by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) in the eastern Nankai Trough (Tokai area) during the 2000–2001 Seize France Japan (SFJ) experiment. We show that the FWI model, although derived from OBS data, provides an acceptable background velocity field for the PSDM of the MCS data. From the initial PSDM, we refine the FWI background velocity model by minimizing the residual move-outs (RMOs) picked in the pre-stack-migrated volume through slope tomography (ST), from which we generate a better-focused migrated image. Such integration of different seismic datasets and leading-edge imaging techniques led to greatly improved imaging at different scales. That is, large to intermediate crustal units identified in the high-resolution FWI velocity model extensively complement the short-wavelength reflectivity inferred from the MCS data to better constrain the structural factors controlling the geodynamics of the Nankai Trough.

Beschreibung: The effects of changes in slope gradient on deposition processes and architecture have been investigated in different deep-sea systems both in modern and ancient environments. However, the impact of subtle gradient changes (

Beschreibung: The upward-tapering channel model proposed by Marques et al. (2018) for the Himalayas has a “base” that forms part of the subducting footwall and therefore does not close the channel. This configuration does not produce return flow, and no dynamic overpressure develops in the channel. The geometrical and kinematic configuration they actually use for their calculations differs from this and is both geologically and mechanically improbable. In addition, the fixed upper boundary condition in their models is mechanically unrealistic and inconsistent with geological and geophysical constraints from the Himalayan orogen. In reality, the dynamic pressures calculated from their model, which exceed lithostatic pressure by as much as 1.5 GPa, would cause elastic flexure or permanent deformation of the upper plate. I estimate that a flexural upwarp of 50 km of the upper plate would be required to balance forces, which would lead to geologically unrealistic topographic and gravity anomalies. The magnitude of the dynamic overpressure that could be confined is in fact limited by the shear strength of the upper plate in the Himalayas, which is likely to be

Beschreibung: Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 ∘C. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of dn-d0n=k0fH2Orexp⁡(-Q/RT)t with grain size d (µm) at time t (seconds), initial grain size d0 (µm), growth exponent n, a constant k0 (µmn MPa−r s−1), water fugacity fH2O (MPa) with the exponent r, activation energy Q (kJ mol−1), gas constant R, and temperature T in Kelvin. The parameters we obtained were n=2.5±0.4, k0=10-8.8±1.4, r=2.3±0.3, and Q=48±34 for the powder and n=2.9±0.4, k0=10-5.8±2.0, r=1.9±0.3, and Q=60±49 for the novaculite. The grain growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks (novaculite), even if the differences between powder and novaculite vanish when grain sizes reach ∼70 µm. Extrapolation of the grain growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is

Beschreibung: The earthquake seismology and seismic exploration communities have developed a variety of seismic imaging methods for passive- and active-source data. Despite the seemingly different approaches and underlying principles, many of those methods are based in some way or another on Green's theorem. The aim of this paper is to discuss a variety of imaging methods in a systematic way, using a specific form of Green's theorem (the homogeneous Green's function representation) as a common starting point. The imaging methods we cover are time-reversal acoustics, seismic interferometry, back propagation, source–receiver redatuming and imaging by double focusing. We review classical approaches and discuss recent developments that fully account for multiple scattering, using the Marchenko method. We briefly indicate new applications for monitoring and forecasting of responses to induced seismic sources, which are discussed in detail in a companion paper.

Beschreibung: Interpretation of deep seismic data is challenging due to the lack of direct geological constraints from drilling and the more limited amount of data available from 2-D profiles in comparison to hydrocarbon exploration surveys. Thus other constraints that can be derived from the seismic data themselves can be of great value. Though the origin of most deep seismic reflections remains ambiguous, an association between seismic reflections and crustal strain, e.g. shear zones, underlies many interpretations. Estimates of the 3-D orientation of reflectors may help associate specific reflections, or regions of the crust, with geological structures mapped at the surface whose orientation and tectonic history are known. In the case of crooked 2-D onshore seismic lines, the orientation of reflections can be estimated when the range of azimuths in a common midpoint gather is greater than approximately 20∘, but integration of these local orientation attributes into an interpretation of migrated seismic data requires that they also be migrated. Here we present a simple approach to the 2-D migration of these orientation attributes that utilizes the apparent dip in reflections on the unmigrated stack and maps reflector strike, for example, to a short linear segment depending on its original position and a migration velocity. This interpretation approach has been applied to a seismic line shot across the Younami Terrane of the Australian Yilgarn Craton and indicates that the lower crust behaved differently from the overlying middle crust as the newly assembled crust collapsed during the Late Archean. Some structures related to approximately east-directed shortening are preserved in the middle crust, but the lower crust is characterized by reflectors that suggest N-NNE-oriented ductile flow. Deployment of off-line receivers during seismic acquisition allows the recording of a larger range of source-receiver azimuths and should produce more reliable future estimates of these reflector attributes.

Beschreibung: The Kirthar Fold Belt is part of the transpressive transfer zone in Pakistan linking the Makran accretionary wedge with the Himalaya orogeny. The region is deforming very obliquely, nearly parallel to the regional S–N plate motion vector, indicating strong strain partitioning. In the central Kirthar Fold Belt, folds trend roughly N–S and their structural control is poorly understood. In this study, we use newly acquired 2-D seismic data with pre-stack depth migration, published focal mechanisms, surface and subsurface geological data, and structural modelling with restoration and balancing to constrain the structural architecture and kinematics of the Kirthar Fold Belt. The central Kirthar Fold Belt is controlled by Pliocene to recent linked thick-skinned to thin-skinned deformation. The thick-skinned faults are most likely partially inverting rift-related normal faults. Focal mechanisms indicate dip-slip faulting on roughly N–S-trending faults with some dip angles exceeding 40∘, which are considered too steep for newly initiated thrust faults. The hinterland of the study area is primarily dominated by strike-slip faulting. The inverting faults do not break straight through the thick sedimentary column of the post-rift and flexural foreland; rather, the inversion movements link with a series of detachment horizons in the sedimentary cover. Large-scale folding and layer-parallel shortening has been observed in the northern study area. In the southern study area progressive imbrication of the former footwall of the normal fault is inferred. Due to the presence of a thick incompetent upper unit (Eocene Ghazij shales) these imbricates develop as passive roof duplexes. In both sectors the youngest footwall shortcut links with a major detachment and the deformation propagates to the deformation front, forming a large fault-propagation fold. Shortening within the studied sections is calculated to be 18 %–20 %. The central Kirthar Fold Belt is a genuine example of a hybrid thick- and thin-skinned system in which the paleogeography controls the deformation. The locations and sizes of the former rift faults control the location and orientation of the major folds. The complex tectonostratigraphy (rift, post-rift, flexural foreland) and strong E–W gradients define the mechanical stratigraphy, which in turn controls the complex thin-skinned deformation.

Beschreibung: Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580 ∘C, but current methods underestimate the range of uncertainty. We formulate the estimation of Curie depth within a Bayesian framework to quantify its uncertainty across the British Isles. Uncertainty increases exponentially with Curie depth but this can be moderated by increasing the size of the spatial window taken from the magnetic anomaly. The choice of window size needed to resolve the magnetic thickness is often ambiguous but, based on our chosen spectral method, we determine that significant gains in precision can be obtained with window sizes 15–30 times larger than the deepest magnetic source. Our Curie depth map of the British Isles includes a combination of window sizes: smaller windows are used where the magnetic base is shallow to resolve small-scale features, and larger window sizes are used where the magnetic base is deep in order to improve precision. On average, the Curie depth increases from Laurentian crust (22.2±5.3 km) to Avalonian crust (31.2±9.2 km). The temperature distribution in the crust, and associated uncertainty, was simulated from the ensemble of Curie depth realizations assigned to a lower thermal boundary condition of a crustal model (sedimentary thickness, Moho depth, heat production, thermal conductivity), constructed from various geophysical and geochemical datasets. The uncertainty in the simulated heat flow field substantially increases from ±10 mW m−2 for shallow Curie depths at ∼15 km to ±80 mW m−2 for Curie depths 〉40 km. Surface heat flow observations are concordant with the simulated heat flow field except in regions that contain igneous bodies. Heat flow data within large batholiths in the British Isles exceed the simulated heat flow by ∼25 mW m−2 as a result of their high rates of heat production (4–6 µW m−3). Conversely, heat refraction around thermally resistive mafic volcanics and thick sedimentary layers induce a negative heat flow misfit of a similar magnitude. A northward thinning of the lithosphere is supported by shallower Curie depths on the northern side of the Iapetus Suture, which separates Laurentian and Avalonian terranes. Cenozoic volcanism in Northern Britain and Ireland has previously been attributed to a lateral branch of the proto-Icelandic mantle plume. Our results show that high surface heat flow (〉90 mW m−2) and shallow Curie depth (∼15 km) occur within the same region, which supports the hypothesis that lithospheric thinning occurred due to the influence of a mantle plume. The fact that the uncertainty is only ±3–8 km in this region demonstrates that Curie depths are more reliable in hotter regions of the crust where the magnetic base is shallow.

Beschreibung: Numerous studies have revealed genetic similarities between Tethyan ophiolites and oceanic “proto-arc” sequences formed above nascent subduction zones. The Semail ophiolite (Oman–U.A.E.) in particular can be viewed as an analogue for this proto-arc crust. Though proto-arc magmatism and the mechanisms of subduction initiation are of great interest, insight is difficult to gain from drilling and limited surface outcrops in marine settings. In contrast, the 3–5 km thick upper-crustal succession of the Semail ophiolite, which is exposed in an oblique cross section, presents an opportunity to assess the architecture and volumes of different volcanic rocks that form during the proto-arc stage. To determine the distribution of the volcanic rocks and to aid exploration for the volcanogenic massive sulfide (VMS) deposits that they host, we have remapped the volcanic units of the Semail ophiolite by integrating new field observations, geochemical analyses, and geophysical interpretations with pre-existing geological maps. By linking the major-element compositions of the volcanic units to rock magnetic properties, we were able to use aeromagnetic data to infer the extension of each outcropping unit below sedimentary cover, resulting in a new map showing 2100 km2 of upper-crustal bedrock. Whereas earlier maps distinguished two main volcanostratigraphic units, we have distinguished four, recording the progression from early spreading-axis basalts (Geotimes), through axial to off-axial depleted basalts (Lasail), to post-axial tholeiites (Tholeiitic Alley), and finally boninites (Boninitic Alley). Geotimes (“Phase 1”) axial dykes and lavas make up ∼55 vol % of the Semail upper crust, whereas post-axial (“Phase 2”) lavas constitute the remaining ∼45 vol % and ubiquitously cover the underlying axial crust. Highly depleted boninitic members of the Lasail unit locally occur within and directly atop the axial sequence, marking an earlier onset of boninitic magmatism than previously known for the ophiolite. The vast majority of the Semail boninites, however, belong to the Boninitic Alley unit and occur as discontinuous accumulations up to 2 km thick at the top of the ophiolite sequence and constitute ∼15 vol % of the upper crust. The new map provides a basis for targeted exploration of the gold-bearing VMS deposits hosted by these boninites. The thickest boninite accumulations occur in the Fizh block, where magma ascent occurred along crustal-scale faults that are connected to shear zones in the underlying mantle rocks, which in turn are associated with economic chromitite deposits. Locating major boninite feeder zones may thus be an indirect means to explore for chromitites in the underlying mantle.

Beschreibung: Structural uncertainty is a key parameter affecting the accuracy of the information contained in static and dynamic reservoir models. However, quantifying and assessing its real impact on reservoir property distribution, in-place volume estimates and dynamic simulation has always been a challenge. Due to the limitation of the existing workflows and time constraints, the exploration of all potential geological configurations matching the interpreted data has been limited to a small number of scenarios, making the future field development decisions uncertain. We present a case study in the Lubina and Montanazo mature oil fields (Western Mediterranean) in which the structural uncertainty in the seismic interpretation of faults and horizons has been captured using modern reservoir modeling workflows. We model the fault and horizon uncertainty by means of two workflows: the manually interpreted and the constant uncertainty cases. In the manually interpreted case, the zones of ambiguity in the position of horizons and faults are defined as locally varying envelopes around the best interpretation, whose dimensions mainly vary according to the frequency content of the seismic data, lateral variations of amplitudes along reflectors, and how the reflectors terminate around faults when fault reflections are not present in the seismic image. In the constant case, the envelope dimensions are kept constant for each horizon and each fault. Both faults and horizons are simulated within their respective uncertainty envelopes as provided to the user. In all simulations, conditioning to available well data is ensured. Stochastic simulation was used to obtain 200 realizations for each uncertainty modeling workflow. The realizations were compared in terms of gross rock volumes above the oil–water contact considering three scenarios at the depths of the contact. The results show that capturing the structural uncertainty in the picking of horizons and faults in seismic data has a relevant impact on the volume estimation. The models predict percentage differences in the mean gross rock volume with respect to best-estimate interpretation up to 7 % higher and 12 % lower (P10 and P90). The manually interpreted uncertainty workflow reports narrower gross rock volume predictions and more consistent results from the simulated structural models than the constant case. This work has also revealed that, for the Lubina and Montanazo fields, the fault uncertainty associated with the major faults that bound the reservoir laterally strongly affects the gross rock volume predicted. The multiple realizations obtained are geologically consistent with the available data, and their differences in geometry and dimensions of the reservoir allow us to improve the understanding of the reservoir structure. The uncertainty modeling workflows applied are easy to design and allow us to update the models when required. This work demonstrates that knowledge of the data and the sources of uncertainty is important to set up the workflows correctly. Further studies can combine other sources of uncertainty in the modeling process to improve the risk assessment.

Beschreibung: In source regions of magmatic systems the temperature is above solidus, and melt ascent is assumed to occur predominantly by two-phase flow, which includes a fluid phase (melt) and a porous deformable matrix. Since McKenzie (1984) introduced equations for two-phase flow, numerous solutions have been studied, one of which predicts the emergence of solitary porosity waves. By now most analytical and numerical solutions for these waves used strongly simplified models for the shear- and bulk viscosity of the matrix, significantly overestimating the viscosity or completely neglecting the porosity dependence of the bulk viscosity. Schmeling et al. (2012) suggested viscosity laws in which the viscosity decreases very rapidly for small melt fractions. They are incorporated into a 2-D finite difference mantle convection code with two-phase flow (FDCON) to study the ascent of solitary porosity waves. The models show that, starting with a Gaussian-shaped wave, they rapidly evolve into a solitary wave with similar shape and a certain amplitude. Despite the strongly weaker rheologies compared to previous viscosity laws, the effects on dispersion curves and wave shape are only moderate as long as the background porosity is fairly small. The models are still in good agreement with semi-analytic solutions which neglect the shear stress term in the melt segregation equation. However, for higher background porosities and wave amplitudes associated with a viscosity decrease of 50 % or more, the phase velocity and the width of the waves are significantly decreased. Our models show that melt ascent by solitary waves is still a viable mechanism even for more realistic matrix viscosities.

Beschreibung: The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project “Drilling the Eger Rift” in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it. As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole–dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 and 150 m dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. −9 mGal marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as CO2. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.

Beschreibung: Measurements of seismic velocity as a function of depth are generally restricted to borehole locations and are therefore sparse in the world's oceans. Consequently, in the absence of measurements or suitable seismic data, studies requiring knowledge of seismic velocities often obtain these from simple empirical relationships. However, empirically derived velocities may be inaccurate, as they are typically limited to certain geological settings, and other parameters potentially influencing seismic velocities, such as depth to basement, crustal age, or heat flow, are not taken into account. Here, we present a machine learning approach to predict the overall trend of seismic P-wave velocity (vp) as a function of depth (z) for any marine location. Based on a training dataset consisting of vp(z) data from 333 boreholes and 38 geological and spatial predictors obtained from publicly available global datasets, a prediction model was created using the random forests method. In 60 % of the tested locations, the predicted seismic velocities were superior to those calculated empirically. The results indicate a promising potential for global prediction of vp(z) data, which will allow the improvement of geophysical models in areas lacking first-hand velocity data.

Beschreibung: Observations from permanent Global Navigation Satellite System (GNSS) stations are commonly used to correct tide-gauge observations for vertical land motion (VLM). We combine GRACE (Gravity Recovery and Climate Experiment) observations and an ensemble of glacial isostatic adjustment (GIA) predictions to assess and evaluate the impact of solid-Earth deformation (SED) due to contemporary mass redistribution and GIA on VLM trends derived from GNSS stations. This mass redistribution causes relative sea-level (RSL) and SED patterns that not only vary in space but also exhibit large interannual variability signals. We find that for many stations, including stations in coastal locations, this deformation causes VLM trends on the order of 1 mm yr−1 or higher. In multiple regions, including the Amazon Basin and large parts of Australia, the SED trend flips sign between the first half and second half of the 15-year GRACE record. GNSS records often only span a few years, and due to these interannual variations SED causes substantial biases when the linear trends in these short records are extrapolated back in time. We propose a new method to avoid this potential bias in the VLM-corrected tide-gauge record: instead of correcting tide-gauge records for the observed VLM trend, we first remove the effects from GIA and contemporary mass redistributions from the VLM observations before computing the VLM trend. This procedure reduces the extrapolation bias induced by SED, and it also avoids the bias due to sea-floor deformation: SED includes net sea-floor deformation, which is ignored in global-mean sea-level reconstructions based on VLM-corrected tide-gauge data. We apply this method to 8166 GNSS stations. With this separation, we are able to explain a large fraction of the discrepancy between observed sea-level trends at multiple long tide-gauge records and the global-mean sea-level trend from recent reconstructions.

Beschreibung: Uncertainties are common in geological models and have a considerable impact on model interpretations and subsequent decision-making. This is of particular significance for high-risk, high-reward sectors. Recent advances allows us to view geological modeling as a statistical problem that we can address with probabilistic methods. Using stochastic simulations and Bayesian inference, uncertainties can be quantified and reduced by incorporating additional geological information. In this work, we propose custom loss functions as a decision-making tool that builds upon such probabilistic approaches. As an example, we devise a case in which the decision problem is one of estimating the uncertain economic value of a potential fluid reservoir. For subsequent true value estimation, we design a case-specific loss function to reflect not only the decision-making environment, but also the preferences of differently risk-inclined decision makers. Based on this function, optimizing for expected loss returns an actor's best estimate to base decision-making on, given a probability distribution for the uncertain parameter of interest. We apply the customized loss function in the context of a case study featuring a synthetic 3-D structural geological model. A set of probability distributions for the maximum trap volume as the parameter of interest is generated via stochastic simulations. These represent different information scenarios to test the loss function approach for decision-making. Our results show that the optimizing estimators shift according to the characteristics of the underlying distribution. While overall variation leads to separation, risk-averse and risk-friendly decisions converge in the decision space and decrease in expected loss given narrower distributions. We thus consider the degree of decision convergence to be a measure for the state of knowledge and its inherent uncertainty at the moment of decision-making. This decisive uncertainty does not change in alignment with model uncertainty but depends on alterations of critical parameters and respective interdependencies, in particular relating to seal reliability. Additionally, actors are affected differently by adding new information to the model, depending on their risk affinity. It is therefore important to identify the model parameters that are most influential for the final decision in order to optimize the decision-making process.

Beschreibung: We present the implementation of Thomsen's weak anisotropy approximation for vertical transverse isotropy (VTI) media within TOMO3D, our code for 2-D and 3-D joint refraction and reflection travel-time tomographic inversion. In addition to the inversion of seismic P-wave velocity and reflector depth, the code can now retrieve models of Thomsen's parameters (δ and ε). Here, we test this new implementation following four different strategies on a canonical synthetic experiment in ideal conditions with the purpose of estimating the maximum capabilities and potential weak points of our modeling tool and strategies. First, we study the sensitivity of travel times to the presence of a 25 % anomaly in each of the parameters. Next, we invert for two combinations of parameters (v, δ, ε and v, δ, v⊥), following two inversion strategies, simultaneous and sequential, and compare the results to study their performance and discuss their advantages and disadvantages. Simultaneous inversion is the preferred strategy and the parameter combination (v, δ, ε) produces the best overall results. The only advantage of the parameter combination (v, δ, v⊥) is a better recovery of the magnitude of v. In each case, we derive the fourth parameter from the equation relating ε, v⊥ and v. Recovery of v, ε and v⊥ is satisfactory, whereas δ proves to be impossible to recover even in the most favorable scenario. However, this does not hinder the recovery of the other parameters, and we show that it is still possible to obtain a rough approximation of the δ distribution in the medium by sampling a reasonable range of homogeneous initial δ models and averaging the final δ models that are satisfactory in terms of data fit.

Beschreibung: Active fumarolic solfataric zones represent important structures of dormant volcanoes, but unlike emitted fluids, their mineralizations are omitted in the usual monitoring activity. This is the case of the Campi Flegrei caldera in Italy, among the most hazardous and best-monitored explosive volcanoes in the world, where the landscape of Puteoli is characterized by an acid sulfate alteration that has been active at least since Roman time. This paper provides temperature, mineralogical, textural, compositional and stable isotope data for those solfataric terrains sampled at the crater and Pisciarelli slope of the Solfatara volcano between 2013 and 2019. Temperatures vary between 40 and 95 ∘C. Minerals include alunite with grain sizes generally larger than 20 µm, alunogen, native sulfur, well-ordered kaolinite, and, common at Pisciarelli, pyrite, illite and NH4 sulfates. Sulfate terrains have higher contents of Ti, Ba, Au, As, Hg and Tl relative to their parent substrate. The Pisciarelli slope is anomalous in terms of the presence of NH4. δ34S values for sulfides and native S range between −3.00 ‰ and 0.49 ‰ and from −4.42 ‰ to 0.80 ‰, respectively. Sulfates show δ34S and δ18O values in the range of −2.78 ‰ to 2.09 ‰ and between 4.60 ‰ and 31.33 ‰, respectively. The style of mineralization and the stable isotope geochemistry do produce complex and not completely consistent classifications and genetic constraints. We merge our data with volcanological information, data from exploration drillings and geophysical results. With the conceptual model, we suggest a series of shallow and deep aquifers interconnected like “communicating vessels” through a main fault system that downthrows Solfatara with respect to Pisciarelli. Fluid outflow from the different discrete aquifers hosted in sediments – and possibly bearing organic imprints – is the main dataset that allows determination of the steam-heated environment with a supergene setting superimposed. Supergene conditions and high-sulfidation relicts, together with the narrow sulfate alteration zone buried under the youngest volcanic deposits, point to the existence of an evolving paleo-conduit. The data will contribute to monitoring and evaluating the volcanic hazards.

Beschreibung: We present a high-resolution P-wave velocity model of the sedimentary cover and the uppermost basement to ∼3 km depth obtained by full-waveform inversion of multichannel seismic data acquired with a 6 km long streamer in the Alboran Sea (SE Iberia). The inherent non-linearity of the method, especially for short-offset, band-limited seismic data as this one, is circumvented by applying a data processing or modelling sequence consisting of three steps: (1) data re-datuming by back-propagation of the recorded seismograms to the seafloor; (2) joint refraction and reflection travel-time tomography combining the original and the re-datumed shot gathers; and (3) full-waveform inversion of the original shot gathers using the model obtained by travel-time tomography as initial reference. The final velocity model shows a number of geological structures that cannot be identified in the travel-time tomography models or easily interpreted from seismic reflection images alone. A sharp strong velocity contrast accurately defines the geometry of the top of the basement. Several low-velocity zones that may correspond to the abrupt velocity change across steeply dipping normal faults are observed at the flanks of the basin. A 200–300 m thick, high-velocity layer embedded within lower-velocity sediment may correspond to evaporites deposited during the Messinian crisis. The results confirm that the combination of data re-datuming and joint refraction and reflection travel-time inversion provides reference models that are accurate enough to apply full-waveform inversion to relatively short offset streamer data in deep-water settings starting at a field-data standard low-frequency content of 6 Hz.

Beschreibung: As part of the In-situ Stimulation and Circulation (ISC) experiment, hydraulic fracturing (HF) tests were conducted in a moderately fractured crystalline rock mass at the Grimsel Test Site (GTS), Switzerland. The aim of these injection tests was to improve our understanding of processes associated with high-pressure fluid injection. A total of six HF experiments were performed in two inclined boreholes; the surrounding rock mass was accessed with 12 observation boreholes, which allows for the high-resolution monitoring of fracture fluid pressure, strain, and microseismicity in an exceptionally well-characterized rock mass. A similar injection protocol was used for all six experiments to investigate the complexity of the fracture propagation processes. At the borehole scale, these processes involved newly created tensile fractures intersecting the injection interval, while at the cross-hole scale, the natural network of fractures dominated the propagation process. The six HF experiments can be divided into two groups based on their injection location (i.e., south or north to a brittle–ductile shear zone), their similarity of injection pressures, and their response to deformation and pressure propagation. The injection tests performed in the south connect upon propagation to the brittle–ductile shear zone. Thus, the shear zone acts as a dominant drain and a constant pressure boundary. The experiments executed north of the shear zone show smaller injection pressures and larger backflow during bleed-off phases. From a seismic perspective, the injection tests show high variability in seismic response independently of the location of injection. For two injection experiments, we observe reorientation of the seismic cloud as the fracture propagated away from the wellbore. In both cases, the main propagation direction is normal to the minimum principal stress direction. The reorientation during propagation is interpreted to be related to a strong stress heterogeneity and the intersection of natural fractures striking differently than the propagating hydraulic fracture. The seismic activity was limited to about 10 m of radial distance from the injection point. In contrast, strain and pressure signals reach further into the rock mass, indicating that the process zone around the injection point is larger than the zone illuminated by seismic signals. Furthermore, strain signals indicate not just single fracture openings but also the propagation of multiple fractures. Transmissivities of injection intervals increase about 2–4 orders of magnitudes.

Beschreibung: The magmatism (including volcanism) in East Asia (or China) could provide key clues and age constraints for the subduction and dynamical process of the Paleo-Pacific Plate. Although many absolute isotope ages of extrusive rocks have been published in the 1980s–2000s, large uncertainties and large errors prevent the magmatism in southeast (SE) China from being well understood. In this study, we investigate the zircon geochronology of extrusive rocks and temporospatial variations in the late Mesozoic volcanism in SE China. We reported zircon U–Pb ages of new 48 extrusive rock samples in the Shi-Hang tectonic belt. Together with the published data in the past decade, ages of 291 rock samples from ∼40 lithostratigraphic units were compiled, potentially documenting a relatively complete history and spatial distribution of the late Mesozoic volcanism in SE China. The results show that the extrusive rocks spanned ∼95 Myr (177–82 Ma), but dominantly ∼70 Myr (160–90 Ma), within which the volcanism in the early Early Cretaceous (145–125 Ma) was the most intensive and widespread eruption. We propose that these ages represent the intervals of the Yanshanian volcanism in SE China. Spatially, the age geographic pattern of extrusive rocks shows that both the oldest and youngest age clusters occur in the coastal magmatic arc (eastern Zhejiang and Fujian), and the most intensive and widespread age group (145–125 Ma) occurs in a back arc or rifting basin (eastern Jiangxi, central Zhejiang, and northern Guangdong), implying that the late Mesozoic volcanism migrated northwest and subsequently retreated southeast. This volcanic migration pattern may imply that the Paleo-Pacific Plate subducted northwestward and the roll-back subduction did not begin until the Aptian (∼125 Ma) of the mid-Cretaceous.

Beschreibung: The Alpine orogen formed as a result of the collision between the Adriatic and European plates. Significant crustal heterogeneity exists within the region due to the long history of interplay between these plates, other continental and oceanic blocks in the region, and inherited crustal features from earlier orogenies. Deformation relating to the collision continues to the present day. Here, a seismically constrained, 3-D structural and density model of the lithosphere of the Alps and their respective forelands, derived from integrating numerous geoscientific datasets, was adjusted to match the observed gravity field. It is shown that the distribution of seismicity and deformation within the region correlates well to thickness and density changes within the crust, and that the present-day Adriatic crust is both thinner and denser (22.5 km, 2800 kg m−3) than the European crust (27.5 km, 2750 kg m−3). Alpine crust derived from each respective plate is found to show the same trend, with zones of Adriatic provenance (Austro-Alpine unit and Southern Alps) found to be denser and those of European provenance (Helvetic zone and Tauern Window) to be less dense. This suggests that the respective plates and related terranes had similar crustal properties to the present-day ones prior to orogenesis. The model generated here is available for open-access use to further discussions about the crust in the region.

Beschreibung: The stratigraphic architecture of the Swiss Molasse basin, situated on the northern side of the evolving Alps, reveals crucial information about the basin's geometry, its evolution, and the processes leading to the deposition of the siliciclastic sediments. Nevertheless, the formation of the Upper Marine Molasse (OMM) and the controls on the related Burdigalian transgression have still been a matter of scientific debate. During the time period from ca. 20 to 17 Ma, the Swiss Molasse basin was partly flooded by a shallow marine sea striking SW–NE. Previous studies have proposed that the transgression occurred in response to a rise in global sea level, a reduction of sediment flux, or an increase in tectonically controlled accommodation space. Here, we readdress this problem and extract stratigraphic signals from the Burdigalian molasse deposits that can be related to changes in sediment supply rate, variations in the eustatic sea level, and subduction tectonics. To achieve this goal, we conducted sedimentological and stratigraphic analyses of several sites across the entire Swiss Molasse basin. Field investigations show that the transgression and the subsequent evolution of the Burdigalian seaway was characterized by (i) a deepening and widening of the basin, (ii) phases of erosion and non-deposition during Lower Freshwater Molasse (USM), OMM, and Upper Freshwater Molasse (OSM) times, and (iii) changes in along-strike drainage reversals. We use these changes in the stratigraphic record to disentangle tectonic and surface controls on the facies evolution at various scales. As the most important mechanism, rollback subduction of the European mantle lithosphere most likely caused a further downwarping of the foreland plate, which we use to explain the deepening and widening of the Molasse basin, particularly at distal sites. In addition, subduction tectonics also caused the uplift of the Aar massif. This process was likely to have shifted the patterns of surface loads, thereby resulting in a buckling of the foreland plate and influencing the water depths in the basin. We use this mechanism to explain the establishment of distinct depositional settings, particularly the formation of subtidal shoals wherein a bulge in relation to this buckling is expected. The rise of the Aar massif also resulted in a reorganization of the drainage network in the Alpine hinterland, with the consequence that the sediment flux to the basin decreased. We consider this reduction in sediment supply to have amplified the tectonically controlled deepening of the Molasse basin. Because the marine conditions were generally very shallow, subtle changes in eustatic sea level contributed to the formation of several hiatuses that chronicle periods of erosion and non-sedimentation. These processes also amplified the tectonically induced increase in accommodation space during times of global sea level highstands. Whereas these mechanisms are capable of explaining the establishment of the Burdigalian seaway and the formation of distinct sedimentological niches in the Swiss Molasse basin, the drainage reversal during OMM times possibly requires a change in tectonic processes at the slab scale, most likely including the entire Alpine range between the Eastern and Central Alps. In conclusion, we consider rollback tectonics to be the main driving force controlling the transgression of the OMM in Switzerland, with contributions by the uplift of individual crustal blocks (here the Aar massif) and by a reduction of sediment supply. This reduction of sediment flux was likely to have been controlled by tectonic processes as well when basement blocks became uplifted, thereby modifying the catchment geometries. Eustatic changes in sea level explain the various hiatuses and amplified the deepening of the basin during eustatic highstand conditions.

Beschreibung: This paper presents an alternative approach for estimating the Biot coefficient for the Grimsel granite, which appeals to the multi-phasic mineralogical composition of the rock. The modelling considers the transversely isotropic nature of the rock that is evident from both the visual appearance of the rock and determined from mechanical testing. Conventionally, estimation of the compressibility of the solid material is performed by fluid saturation of the pore space and pressurization. The drawback of this approach in terms of complicated experimentation and influences of the unsaturated pore space is alleviated by adopting the methods for estimating the solid material compressibility using developments in theories of multi-phase materials. The results of the proposed approach are compared with estimates available in the literature.

Beschreibung: The Spanish Central System is an intraplate mountain range that divides the Iberian Inner Plateau in two sectors – the northern Duero Basin and the Tajo Basin to the south. The topography of the area is highly variable with the Tajo Basin having an average altitude of 450–500 m and the Duero Basin having a higher average altitude of 750–800 m. The Spanish Central System is characterized by a thick-skin pop-up and pop-down configuration formed by the reactivation of Variscan structures during the Alpine orogeny. The high topography is, most probably, the response of a tectonically thickened crust that should be the response to (1) the geometry of the Moho discontinuity, (2) an imbricated crustal architecture, and/or (3) the rheological properties of the lithosphere. Shedding some light on these features is the main target of the current investigation. In this work, we present the lithospheric-scale model across this part of the Iberian Massif. We have used data from the Central Iberian Massif Deformation (CIMDEF) project, which consists of recordings of an almost-linear array of 69 short-period seismic stations, which define a 320 km long transect. We have applied the so-called global-phase seismic interferometry. The technique uses continuous recordings of global earthquakes (〉120∘ epicentral distance) to extract global phases and their reverberations within the lithosphere. The processing provides an approximation of the zero-offset reflection response of a single station to a vertical source, sending (near)-vertical seismic energy. Results indeed reveal a clear thickening of the crust below the Central System, resulting, most probably, from an imbrication of the lower crust. Accordingly, the crust–mantle boundary is mapped as a relatively flat interface at approximately 10 s two-way travel time except in the Central System, where this feature deepens towards the NW reaching more than 12 s. The boundary between the upper and lower crust is well defined and is found at 5 s two-way travel time. The upper crust has a very distinctive signature depending on the region. Reflectivity at upper-mantle depths is scattered throughout the profile, located between 13 and 18 s, and probably related to the Hales discontinuity.

Beschreibung: We use 2 decades of data from a dense geodetic network to extract regionally coherent velocities and deformation rates in France and neighboring western European countries. This analysis is combined with statistical tests on synthetic data to quantify the deformation detection thresholds and significance levels. By combining two distinct methods – Gaussian smoothing and k-means clustering – we extract horizontal deformations with a 95 % confidence level of ca. 0.1–0.2 mm yr−1 (ca. 0.5–1×10-9 yr−1) on spatial scales of 100–200 km or more. From these analyses, we show that the regionally average velocity and strain rate fields are statistically significant in most of our study area. The first-order deformation signal in France and neighboring western European countries is a belt of N–S to NE–SW shortening of ca. 0.2–0.4 mm yr−1 (1–2×10-9 yr−1) in central and eastern France. In addition to this large-scale signal, patterns of orogen-normal extension are observed in the Alps and the Pyrenees, but methodological biases, mainly related to GPS (Global Positioning System) solution combinations, limit the spatial resolution and preclude associations with specific geological structures. The patterns of deformation in western France show either tantalizing correlation (Brittany) or anticorrelation (Aquitaine Basin) with the seismicity. Overall, more detailed analyses are required to address the possible origin of these signals and the potential role of aseismic deformation.

Beschreibung: The finite physical source problem is usually studied with the concept of volume and time integrals over Green's functions (GFs), representing delta-impulse solutions to the governing partial differential field equations. In seismology, the use of realistic Earth models requires the calculation of numerical or synthetic GFs, as analytical solutions are rarely available. The computation of such synthetic GFs is computationally and operationally demanding. As a consequence, the on-the-fly recalculation of synthetic GFs in each iteration of an optimisation is time-consuming and impractical. Therefore, the pre-calculation and efficient storage of synthetic GFs on a dense grid of source to receiver combinations enables the efficient lookup and utilisation of GFs in time-critical scenarios. We present a Python-based framework and toolkit – Pyrocko-GF – that enables the pre-calculation of synthetic GF stores, which are independent of their numerical calculation method and GF transfer function. The framework aids in the creation of such GF stores by interfacing a suite of established numerical forward modelling codes in seismology (computational back ends). So far, interfaces to back ends for layered Earth model cases have been provided; however, the architecture of Pyrocko-GF is designed to cover back ends for other geometries (e.g. full 3-D heterogeneous media) and other physical quantities (e.g. gravity, pressure, tilt). Therefore, Pyrocko-GF defines an extensible GF storage format suitable for a wide range of GF types, especially handling elasticity and wave propagation problems. The framework assists with visualisations, quality control, and the exchange of GF stores, which is supported through an online platform that provides many pre-calculated GF stores for local, regional, and global studies. The Pyrocko-GF toolkit comes with a well-documented application programming interface (API) for the Python programming language to efficiently facilitate forward modelling of geophysical processes, e.g. synthetic waveforms or static displacements for a wide range of source models.

Beschreibung: We aim to monitor and characterize signals in the subsurface by combining these passive signals with recorded reflection data at the surface of the Earth. To achieve this, we propose a method to create virtual receivers from reflection data using the Marchenko method. By applying homogeneous Green’s function retrieval, these virtual receivers are then used to monitor the responses from subsurface sources. We consider monopole point sources with a symmetric source signal, for which the full wave field without artifacts in the subsurface can be obtained. Responses from more complex source mechanisms, such as double-couple sources, can also be used and provide results with comparable quality to the monopole responses. If the source signal is not symmetric in time, our technique based on homogeneous Green’s function retrieval provides an incomplete signal, with additional artifacts. The duration of these artifacts is limited and they are only present when the source of the signal is located above the virtual receiver. For sources along a fault rupture, this limitation is also present and more severe due to the source activating over a longer period of time. Part of the correct signal is still retrieved, as is the source location of the signal. These artifacts do not occur in another method that creates virtual sources as well as receivers from reflection data at the surface. This second method can be used to forecast responses to possible future induced seismicity sources (monopoles, double-couple sources and fault ruptures). This method is applied to field data, and similar results to the ones on synthetic data are achieved, which shows the potential for application on real data signals.

Beschreibung: The Neogene evolution of the European Alps was characterized by the exhumation of crystalline basement, the so-called external crystalline massifs. Their exhumation presumably controlled the evolution of relief, distribution of drainage networks, and generation of sediment in the Central Alps. However, due to the absence of suitable proxies, the timing of their surficial exposure and thus the initiation of sediment supply from these areas are poorly constrained. The northern Alpine foreland basin preserves the Oligocene to Miocene sedimentary record of tectonic and climatic adjustments in the hinterland. This contribution analyses the provenance of 25 to 14 Myr old alluvial fan deposits by means of detrital garnet chemistry. Unusually grossular- and spessartine-rich garnet is found (1) to be a unique proxy for identifying detritus from the external crystalline massifs and (2) to occur abundantly in ca. 14 Myr old deposits of the foreland basin. In contrast to previous assumptions, we therefore propose that the external massifs were already exposed to the surface ca. 14 Myr ago.