ALBERT

Description: Paleoclimatic effects may still influence the present day subsurface temperature distribution and therefore the heatflow density calculated in affected depth levels. Cooling of several degrees Celsius into depths of up to 1.5 – 2km were reported for areas which were strongly affected by the Pleistocene ice ages (e.g. Canada, Poland, andDenmark). However, although this phenomenon is well known, not much research has been performed to quantifythese processes in Northern Germany, an area where Pleistocene ice margins of the last ice ages are located. Tofill that gap we compiled new data from two boreholes in the eastern part of the North German Basin, one locatedbeneath the former ice shield of the last glaciation, and one located in the foreland. We determined thermal rockproperties (thermal conductivity, thermal diffusivity, and specific heat capacity) on drill core samples and used itas calibrator for well-log based calculations of thermal parameter profiles along the borehole. The results wereused for heat-flow computations with depth and implemented as a base for an analytical solution of the heatequation as well as inversion modelling. By showing the discrepancy of observed and theoretical backgroundtemperature and heat flow density profiles, we aim to improve the understanding of the regional thermal responseto the last glaciations.

Description: The current assessments of the carbon turnover in the Arctic tundra are subject to large uncertainties. This problem can (inter alia) be ascribed to both the general shortage of flux data from the vast and sparsely inhabited Arctic region, as well as the typically high spatiotemporal variability of carbon fluxes in tundra ecosystems. Addressing these challenges, carbon dioxide fluxes on an active flood plain situated in the Siberian Lena River Delta were studied during two growing seasons with the eddy covariance method. The footprint exhibited a heterogeneous surface, which generated mixed flux signals that could be partitioned in such a way that both respiratory loss and photosynthetic gain were obtained for each of two vegetation classes. This downscaling of the observed fluxes revealed a differing seasonality in the net uptake of bushes (−0.89 µmol m−2 s−1) and sedges (−0.38 µmol m−2 s−1) in 2014. That discrepancy, which was concealed in the net signal, resulted from a comparatively warm spring in conjunction with an early snowmelt and a varying canopy structure. Thus, the representativeness of footprints may adversely be affected in response to prolonged unusual weather conditions. In 2015, when air temperatures on average corresponded to climatological means, both vegetation-class-specific flux rates were of similar magnitude (−0.69 µmol m−2 s−1). A comprehensive set of measures (e.g. phenocam) corroborated the reliability of the partitioned fluxes and hence confirmed the utility of flux decomposition for enhanced flux data analysis. This scrutiny encompassed insights into both the phenological dynamic of individual vegetation classes and their respective functional flux to flux driver relationships with the aid of ecophysiologically interpretable parameters. For comparison with other sites, the decomposed fluxes were employed in a vegetation class area-weighted upscaling that was based on a classified high-resolution orthomosaic of the flood plain. In this way, robust budgets that take the heterogeneous surface characteristics into account were estimated. In relation to the average sink strength of various Arctic flux sites, the flood plain constitutes a distinctly stronger carbon dioxide sink. Roughly 42 % of this net uptake, however, was on average offset by methane emissions lowering the sink strength for greenhouse gases. With growing concern about rising greenhouse gas emissions in high-latitude regions, providing robust carbon budgets from tundra ecosystems is critical in view of accelerating permafrost thaw, which can impact the global climate for centuries.

Description: In Northwest Anatolia, the dextral North Anatolian Fault Zone (NAFZ) goes through the Sea of Marmara and cre-ates a section which is known as the Main Marmara Fault (MMF). Due to the NAFZ activity, the Marmara regionis a major earthquake zone. This area hosts the Megacity of Istanbul in the vicinity of a seismic gap (∼150 kmlong) in the MMF which has not ruptured since 1766. There is an ongoing controversial debate regarding the causeof the seismic gap and if either the fault is locked to a certain depth or is creeping. The main question is if the faultis geomechanically segmented or if the energy will be released over a big single rupture surface. To contribute tothis discussion a detailed description and understanding of the lithosphere thermomechanical behaviour below theSea of Marmara is key. In this study, we present 3D lithospheric-scale thermal and rheological models of the Sea ofMarmara. These models are based on a 3D density model which is obtained from geological and geophysical dataintegration and constrained by gravity modelling. Accordingly, the lithosphere structure consists of six major lay-ers. Two layers of syn- and pre-kinematic sediments with respect to the Sea of Marmara formation with an averagedensity (ρ) of 2000 and 2490 kg.m−3, respectively. These sediments rest on a heterogeneous crust including a felsicupper crystalline crust (ρ= 2720 kg.m−3)and an intermediate to mafic lower crystalline crust (ρ= 2890 kg.m−3).The crystalline crustal units are crosscut by two thick dome-shaped mafic high-density bodies (ρ= 3050 kg.m−3),that spatially correlate with the bending segments of the MMF. Beneath these layers is a homogeneous lithosphericmantle (ρ= 3300 kg.m−3)down to the thermal Lithosphere-Asthenosphere boundary (LAB). Along the MMF,the thermomechanical model generally indicates that the brittle-ductile transition zone occurs within the uppercrystalline crust at a depth of around 18 km b.s.l, which is consistent with the 1999 Izmit earthquake. In contrast,the thermomechanical model indicates that the high-density bodies are colder and stronger than the surroundingcrystalline units. Consequently, the brittle-ductile transition zone occurs, closer to the Moho discontinuity, at thedepth around 23 km b.s.l. In conclusion, these results suggest that crustal heterogeneities significantly affect therheological behaviour of the MMF, and support the hypothesis that the fault is geomechanically segmented.

Description: Local earthquake activity can be employed to measure attenuation (the effective quality factor [Q]) and characterize production in the Delaware Basin, Texas, USA. To illustrate this, we employed data from the recently installed Texas Seismic Network (TexNet) seismic stations collected in the west Texas area between April 2017 and March 2018. Earthquake activity in the Delaware Basin has increased in comparison to the previous 20 years, which has resulted in numerous high-quality events suitable for this analysis. The high signal-to-noise ratio events were used to estimate effective Q factors using the peak frequency method on the sediments of the Delaware Basin. The effective attenuation of the sedimentary basin is 90 for P-waves and 140 for S-waves (both with uncertainty of approximately 30), indicating an unusually low attenuation (high Q) for S-waves relative to the P-waves. This is consistent with attenuation of a saturated sedimentary basin because the saturation results in less attenuation of S-waves. Additionally, we observe an increase of the effective Q factor with distance between the station and events consistent with rays sampling the deeper, less-attenuating, and less-saturated portions of the basin and even basement. Inverted effective attenuation coefficients were used to calculate moment magnitudes, which were consistent with those seen in the TexNet array.

Description: Understanding and quantifying total economic impacts of flood events is essential for flood risk management and adaptation planning. Yet, detailed estimations of joint direct and indirect flood-induced economic impacts are rare. In this study an innovative modeling procedure for the joint assessment of short-term direct and indirect economic flood impacts is introduced. The procedure is applied to 19 economic sectors in eight federal states of Germany after the flood events in 2013. The assessment of the direct economic impacts is object-based and considers uncertainties associated with the hazard, the exposed objects and their vulnerability. The direct economic impacts are then coupled to a supply-side Input-Output-Model to estimate the indirect economic impacts. The procedure provides distributions of direct and indirect economic impacts which capture the associated uncertainties. The distributions of the direct economic impacts in the federal states are plausible when compared to reported values. The ratio between indirect and direct economic impacts shows that the sectors Manufacturing, Financial and Insurance activities suffered the most from indirect economic impacts. These ratios also indicate that indirect economic impacts can be almost as high as direct economic impacts. They differ strongly between the economic sectors indicating that the application of a single factor as a proxy for the indirect impacts of all economic sectors is not appropriate.

Description: In summer 2017, the ICDP SUSTAIN project (Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes), drilled three cored boreholes (Table 1) through Surtsey at sites ≤10 m from a cored hole obtained in 1979. Drilling through the still hot volcano was carried out with an Atlas Copco CS1000 drill rig, whose components were transported by helicopter to Surtsey and re-assembled on site. The first vertical borehole, SE-02a, was cored in HQ diameter to 152 meters below surface (m b.s.) during August 7-16. It was terminated due to borehole collapse. A second vertical (SE-02b) cored borehole was then drilled in HQ diameter to 192 m during August 19-26. Wireline borehole logging in SE-02b was performed August 26. The anodized NQ-sized aluminum tubing of the Surtsey Subsurface Observatory was installed in SE-02b to 181 m depth on August 27. A third borehole, SE-03, angled 35° from vertical and directed 264°, was drilled from August 28 to September 4 and reached a measured depth of 354 m (~290 m vertical depth) under the eastern crater. The core is HQ diameter to a measured depth of 213 m and NQ diameter from 213-354 m measured depth. The core traverses the deep conduit and intrusions of the volcano to a total vertical depth of 290 m b.s. Seawater drilling fluid for boreholes SE-02a and SE-02b was filtered and doubly UV-sterilized at the drill site. No mud products were employed while coring SE-02a, while small amounts of attapulgite mud were used in SE-02b and SE-03. Core samples for geochemical analyses of pore water and microbiological investigations were collected on site from all three boreholes. About 650 m of core was transported by helicopter to Heimaey, 18 km northeast of Surtsey, to a processing laboratory where the core was scanned, documented, and described. Additional core processing has taken place at the Náttúrufraedistofnun Íslands, the Icelandic Institute of Natural History in Gardabaer, where both the 1979 and 2017 cores are stored.

Description: Although crustal and sub-crustal structures in the Alps are some of the best studied of any orogen in the world,different hypotheses still exist regarding plate architecture and the nature of the subduction system. Additionally,rheological configurations of the different crustal units and of the lithospheric mantle, isostasy in the orogen-foreland system, and variations of flexural rigidity along and across the mountain belt are, at the present-day, poorlyconstrained with relation to spatial patterns of seismicity and deformation. The primary goal of INTEGRATE,a project in the DFG priority program Mountain Building in 4 Dimensions, a part of the AlpArray initiative,is to provide insights into these questions by integrating different 3D modelling techniques. Here we present agravity constrained, 3D, density differentiated, structural model of the Alps and their respective forelands derivedfrom integrating numerous existing geological and geophysical datasets. Results indicate the existence of lateralheterogeneities within the crust of the studied area, particularly in regards to the difference in thickness and densityof the European and Adriatic crusts. Within the plates, some density heterogeneities correspond to well-studiedtectonic features such as the Vosges, Black Forest and Bohemian massifs, along with the Ivrea geophysical body.However, in keeping with similar modelling works, the location of these density contrasts do not always correspondto present day tectonic structures, instead indicating older, inherited crustal features. A positive correlation betweenthese inherited crustal density contrasts and present day deformation maps of the region was identified, a trendnoted here for the first time. Additionally, we used the 3D density model together with information on seismicvelocities to derive lithologies for the different crustal units and calculate the 3D conductive field of the system. Astemperature is a key controlling factor for rock strength, we also assess the correlation of temperature variationsand deformation within the region.