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  • 551.22  (17)
  • English  (17)
  • 2020-2022  (17)
  • 1970-1974
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  • 1
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    How well does known seismicity between the Lower Rhine Graben and southern North Sea reflect future earthquake activity? (2020)
    Details
    Publication Date: 2021-03-29
    Description: Since the 14th century, moderate seismic activity with 14 earthquakes of magnitude MW≥5.0 occurred in Western Europe in a region extending from the Lower Rhine Graben (LRG) to the southern North Sea. In this paper, we investigate how well this seismic activity could reflect that of the future. The observed earthquake activity in the LRG is continuous and concentrates on the Quaternary normal faults delimiting the LRG, which are also the source of large surface rupturing Holocene and Late Pleistocene earthquakes. The estimated magnitudes of these past earthquakes range from 6.3±0.3 to 7.0±0.3 while their average recurrence on individual faults varies from ten thousand to a few ten thousand years, which makes foreseeing future activity over the long-term possible. Three of the largest historical earthquakes with MW≥5.5 occurred outside the LRG. Late Quaternary activity along the fault zones suspected to be the source of two of these earthquakes, i.e. the 1580 Strait of Dover and 1692 northern Belgian Ardennes earthquakes, is very elusive if it exists. Hence, similar earthquakes would be very infrequent at these locations suggesting that the seismicity outside of the LRG would be episodic and clustered on some faults during periods of a few hundreds of years interrupted by long periods of inactivity typically lasting for some tens to hundreds of thousand years. Seismic moment release estimation and its comparison between recent geological and historical seismicity periods lead us to suggest that the high seismicity level observed between AD 1350 and AD 1700 west of the LRG would be uncommon.
    Description: research
    Keywords: 551.22 ; 550 ; e-docs::Geophysik ; Seismicity ; Earthquake ; Fault zone ; Historical earthquake ; Holocene ; FID-GEO-DE-7
    Language: English
    Type: article_first
    Format: 20
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  • 2
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    The earthquake of September 3, 1770 near Alfhausen (Lower Saxony, Germany): a real, doubtful, or fake event? (2020)
    Details
    Publication Date: 2021-03-29
    Description: In the weekly newspaper of Osnabrück (Germany) of November 3, 1770, a report about a local earthquake was published. Pastor Buck described ground motion effects in the manor ‘Haus Horst’, 1.5 km away from the village of Alfhausen: ‘roof tiles rattled, a chimney fell down, inside the house the top of a stove was overturned, abraded chalk trickled down in all rooms; in the nearby villages, people felt the shaking, and especially the churches suffered noticeably’. The epicentral intensity was estimated to VII (MSK) by Ahorner et al. (1970), but later modified to VI (EMS) by Meier & Grünthal (1992) considering Buck’s report in detail. Since this event is the only documented earthquake in this region, a reliable characterization of its parameters is important. Our re-examination reveals that some reported effects are quite contradictory. Contrary to Buck’s statement, no documents of damages on churches or costs of repairs could be found in the parish registers. As a result, the event appears to be a tectonic earthquake with an epicenter at Alfhausen / Haus Horst. Applying intensity-attenuation relationships, a revised value of the epicentral intensity of I_0≤V (EMS-98) with a focal depth of z≥2 km was derived. A cavity collapse due to leaching processes as a cause of the effects can be ruled out here. However, several details given in the primary source turned out to be unrealistic or at least exaggerated. The tectonic earthquake on September 3, 1770 near Alfhausen should be classified therefore as uncertain or even doubtful.
    Description: research
    Keywords: 551.22 ; 550 ; e-docs::Geophysik ; Lower Saxony ; historical earthquake ; macroseismic intensity ; FID-GEO-DE-7
    Language: English
    Type: article_first
    Format: 17
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  • 3
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    The Paleoseismic Database of Germany and Adjacent Regions PalSeisDB v1.0 (2020)
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    Publication Date: 2021-03-29
    Description: Central Europe is an intraplate domain which is characterized by low to moderate seismicity with records of larger seismic events occurring in historical and recent times. These records of seismicity are restricted to just over one thousand years. This does not reflect the long seismic cycles in Central Europe which are expected to be in the order of tens of thousands of years. Therefore, we have developed a paleoseismic database (PalSeisDB) that documents the records of paleoseismic evidence (trenches, soft-sediment deformation, mass movements, etc.) and extends the earthquake record to at least one seismic cycle. It is intended to serve as one important basis for future seismic hazard assessments. In the compilation of PalSeisDB, paleoseismic evidence features are documented at 129 different locations in the area of Germany and adjacent regions.
    Description: research
    Keywords: 551.22 ; 550 ; e-docs::Geophysik ; Paleoseismology ; Germany ; data base ; Paleoseismic evidence ; FID-GEO-DE-7
    Language: English
    Type: article_first
    Format: 64
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  • 4
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    Collecting macroseismic data in Germany by internet – an overview (2020)
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    Publication Date: 2021-03-29
    Description: Current procedures to collect macroseismic data in Germany are diverse and scattered. At least 10 institutions collect macroseismic data by internet. Several institutes have a long tradition in seismology and have collected macroseismic data using paper forms for many decades. In addition, the responsibilities for geoscientific issues in Germany are a matter of the federal states and several of them have a state earthquake service. The only institution that automatically calculates and maps intensities online in near real time is Erdbebenstation Bensberg in cooperation with the Royal Observatory of Belgium. Baden-Württemberg uses a short form internet questionnaire at the moment. 5 state earthquake services (Bayern, Hessen, Niedersachsen, Rheinland-Pfalz, Sachsen) have implemented the standard German earthquake questionnaire (Kaiser 2014) which is adapted from the standard questionnaire developed by the ESC Working Group on Internet Macroseismology published by Musson & Cecić (2012). Most institutions express their strong need to implement standard procedures for automatic intensity assignment and a standard format for the exchange of questionnaire responses. References Kaiser, D. (2014): Der neue einheitliche Erdbeben-Fragebogen. Mitteilungen / Deutsche Geophysikalische Gesellschaft, 2/2014, 29-33. Musson, R. M. W. & Cecić, I. (2012): Intensity and Intensity Scales. In: New Manual of Seismological Observatory Practice 2 (NMSOP-2).- Deutsches GeoForschungsZentrum GFZ, 1-41; Potsdam. doi:10.2312/GFZ.NMSOP-2_ch12
    Description: lecture
    Keywords: 551.22 ; e-docs::Geophysik ; Macroseismology ; macroseismic survey ; macroseismic data ; FID-GEO-DE-7
    Language: English
    Type: conferencePaper
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  • 5
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    Relationships to Estimate the Magnitude Ms of Historical Earthquakes in Europe from Macroseismic Observations (2020)
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    Publication Date: 2021-03-29
    Description: We develop empirical relationships between the surface wave magnitude MS and macroseismic data, i.e. the epicentral intensity I0, isoseismal radii R(I) of different intensities I and the focal depth h. The basis of this study is formed by carefully selected instrumental parts (since 1900) of 2 earthquake catalogues: Kárník 1996 (Europe and the Mediterranean), and Shebalin et al. 1998 (Central and Eastern Europe). We use the orthogonal regression because we presume that all parameters are in error and because it has the advantage to provide a reversible regression equation. From Shebalin et al.1998 catalogue we obtain MS = 0.65 I0 + 1.90 log(h) – 1.62 with equivalent error δMS = ±0.21. In order to establish a relationship between MS and isoseismal radii we apply a theoretically based model which takes into account both exponential decay and geometrical spreading. From Shebalin et al. 1998catalogue we find MS = 0.673 I + 2.44 log (S(I)) + 0.00163 S(I) – 2.48 with δMS = ±0.28. Here I is the macroseismic intensity (I = 3…9) of the isoseismal in the focal distance S(I) [km]. Kárník 1996 gives isoseismal radii for I = 3 and 5. We obtain: MS = 0.808 I + 2.84 log (S(I)) + 0.00190 S(I) – 3.71 with δMS = ±0.65. These equations make possible reliably estimates of MS . We recommend them for application. The use of high quality data only as input in the regression analysis provides reliable relationships to estimate magnitudes. The magnitude estimation of a historical earthquake from the epicentral intensity gives reliable results only if the focal depth is known well enough. The relationship using isoseismal radii is of greater practical importance as it allows more reliable magnitude estimations of historical earthquakes. We observe regional variations in the relationships which need further investigation.
    Description: poster
    Keywords: 551.22 ; e-docs::Geophysik ; surface wave magnitude ; macroseismic intensity ; orthogonal regression ; historical earthquakes ; FID-GEO-DE-7
    Language: English
    Type: conferencePaper
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  • 6
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    Best practice of macroseismic intensity assessment applied to the earthquake catalogue of southwestern Germany (2020)
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    Publication Date: 2021-03-29
    Description: The earthquake catalogue of southwestern Germany for the last millennium now contains about 30,000 digital macroseismic intensity data points (IDPs). Intensity assessments are based mainly on primary sources using the European Macroseismic Scale 1998 (EMS). The article describes a guideline for best practice of conventional macroseismic evaluation in application to historical and modern-time earthquakes in SW-Germany. Suitability of various diagnostics for intensity assessment is discussed. Assumptions to estimate damage grades and vulnerability classes of buildings are presented. Data restrictions and treatment of special cases are outlined. Further topics are quantification of uncertainties and IDP quality as well as substitutes for intensity. An essential task is to bridge the gap between information from historical sources and seismological needs for use in the earthquake catalogue, thus all issues have a focus on historical earthquakes. Questions of completeness, subjectivity, transparency, and interdisciplinary work are addressed also. Special emphasis is given to a well balanced use of the EMS scale throughout all time periods leading to consistent assessments in the catalogue.
    Description: research
    Keywords: 551.22 ; 550 ; e-docs::Geophysik ; macroseismic intensity ; earthquake catalogue ; European Macroseismic Scale ; damage grade ; vulnerability class ; historical earthquakes ; FID-GEO-DE-7
    Language: English
    Type: article_first
    Format: 29
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  • 7
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    Relationship between magnitude, macroseismic intensity and distance for induced earthquakes in Germany (2020)
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    Publication Date: 2021-03-29
    Description: Induced earthquakes are of public concern and of legal significance if they are felt or if they cause damage. Models to describe the relation between macroseismic intensities, magnitude, and distance from the epicenter or hypocenter are therefore of fundamental importance. With the aim of developing such models for induced earthquakes in Germany, the following data were analyzed: The earthquake database for Germany GERSEIS contains parameters for ~180 induced seismic events with information on magnitude M and intensity I, of which 47 include information on mean isoseismal radii. In addition, the published macroseismic maps of seismic events in mining areas in Germany were evaluated. In Germany, earthquakes caused by mining with moderate to severe building damage (intensity 7 and 8) have so far only occurred in potash and salt mining. Slight building damage (intensity 6) has also been caused by seismic events in coal mining. Over the past 20 years, the frequency of felt earthquakes has increased in regions with natural gas production and in recent years also in regions of deep geothermal energy production. Focal depths show a large influence on the relationship between M and I. Intensity 5 has been observed for shallow (~1 km depth) events with magnitudes as small as ML=1.8. Simple models of the form I = a + b M + c log R, with R = hypocentral distance, can be fitted to the observations. Models for tectonic earthquakes do not fit for induced earthquakes; for induced earthquakes I is smaller for a given M and R. Major differences were found between different mining areas: In natural gas production areas intensity 5 effects were observed at greater hypocentral distances for a given magnitude, compared to coal and potash mining areas. Since macroseismic data (especially intensity data points) in Germany are available almost exclusively in analog form and are often difficult to access, it is necessary to establish a database for induced earthquakes with macroseismic data.
    Description: research
    Keywords: 551.22 ; e-docs::Geophysik ; induced earthquakes ; macroseismic intensity ; mining seismicity ; FID-GEO-DE-7
    Language: English
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  • 8
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    Detection Limits and Near-Field Ground Motions of Fast and Slow Earthquakes (2021)
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    Publication Date: 2021-07-25
    Description: We investigate theoretical limits to detection of fast and slow seismic events, and spatial variations of ground motion expected from M 6 earthquakes at short epicentral distances. The analyses are based on synthetic velocity seismograms calculated with the discrete wavenumber method assuming seismic velocities and attenuation properties of the crust in Southern California. The examined source properties include different magnitudes (M −1.0 to M 6.0), static stress drops (0.1–10 MPa), and slow and fast ruptures (0.1–0.9 of shear wave velocity). For the M 6 events we also consider variations in rise times producing crack- and pulse-type events and different rupture directivities. Slow events produce ground motion with considerably lower amplitude than corresponding regular fast earthquakes with the same magnitude, and hence are significantly more difficult to detect. The static stress drop and slip rise time also affect the maximum radiated seismic motion, and hence event detectability. Apart from geometrical factors, the saturation and depletion of seismic ground motion at short epicentral distances stem from radiation pattern, earthquake size (magnitude, stress drop), and rupture directivity. The rupture velocity, rise time, and directivity affect significantly the spatial pattern of the ground motions. The results can help optimizing detection of slow and fast small earthquakes and understand the spatial distribution of ground motion generated by large events.
    Keywords: 551.22 ; slow earthquakes ; ground motions ; earthquake detection ; source parameters
    Language: English
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  • 9
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    Is Coulomb Stress the Best Choice for Aftershock Forecasting? (2021)
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    Publication Date: 2021-07-24
    Description: The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance-slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half-space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half-space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance-slip probabilistic model.
    Keywords: 551.22
    Language: English
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  • 10
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    Introduction: Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard: New Insights and Suggested Procedures (2020)
    Details
    Publication Date: 2021-03-29
    Description: This publication developed from the 5th International Colloquium on “Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard” which was held from 11 to 13 October 2017 at the Federal Institute for Geosciences and Natural Resources (BGR) in Hannover, Germany. It comprises four contributions: Brüstle, W., Braumann, U., Hock, S. & Rodler, F.-A. (2020). Best practice of macroseismic intensity assessment applied to the earthquake catalogue of southwestern Germany. In: Kaiser, D. (Ed.). Historical Earthquakes, Paleoseismology, Neotectonics, and Seismic Hazard: New Insights and Suggested Procedures, DGEB-Publikation 18, Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik. doi: 10.23689/fidgeo-3864 Camelbeeck, T., Vanneste, K., Verbeeck, K., Garcia-Moreno, D., Van Noten, K. & Lecocq, T. (2020). How well does known seismicity between the Lower Rhine Graben and southern North Sea reflect future earthquake activity? In: Kaiser, D. (Ed.). Historical Earthquakes, Paleoseismology, Neotectonics, and Seismic Hazard: New Insights and Suggested Procedures, DGEB-Publikation 18, Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik. doi: 10.23689/fidgeo-3866 Hürtgen, J., Reicherter, K., Spies, T., Geisler, C. & Schlittenhardt, J. (2020). The Paleoseismic Database of Germany and Adjacent Regions PalSeisDB v1.0. In: Kaiser, D. (Ed.). Historical Earthquakes, Paleoseismology, Neotectonics, and Seismic Hazard: New Insights and Suggested Procedures, DGEB-Publikation 18, Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik. doi: 10.23689/fidgeo-3867 Leydecker, G. & Lehmann, K. (2020). The earthquake of September 3, 1770 near Alfhausen (Lower Saxony, Germany): a real, doubtful, or a fake event? In: Kaiser, D. (Ed.). Historical Earthquakes, Paleoseismology, Neotectonics, and Seismic Hazard: New Insights and Suggested Procedures, DGEB-Publikation 18, Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik. doi: 10.23689/fidgeo-3865
    Description: Introduction to DGEB-Publikation Nr. 18 Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik (DGEB)
    Description: editorial
    Keywords: 551.22 ; 550 ; e-docs::Geophysik ; Historical earthquakes ; Paleoseismology ; macroseismic intensity ; neotectonics ; FID-GEO-DE-7
    Language: English
    Type: article_first
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  • 11
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    Elastic Fault Interactions and Earthquake Rupture Along the Southern Hellenic Subduction Plate Interface Zone in Greece (2021)
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    Publication Date: 2021-09-27
    Description: The importance of splay-thrust faults in subduction seismogenesis is increasingly acknowledged; however, their elastic interaction with the plate interface remains unclear. Here, we use GPS velocities, constrained by millennial fault slip rates, to study elastic fault-interactions between the plate interface and its upper-plate splay-thrust faults from the southern Hellenic Subduction System (HSS). We find that, despite its largely aseismic character, the HSS plate interface zone is kinematically segmented, with slip rate deficits locally reaching ~85% and ~45% of the plate convergence rate on the western and eastern segments, respectively, and on structures different from those that ruptured historically. Although western Crete has been more active seismically during late Holocene, we find that the eastern HSS has higher seismic potential for large-magnitude (M 〉 6) earthquakes and its interface zone is closer to failure. Elastic fault interactions are responsible for both significant intersegment variability in strain accumulation and uniformity in earthquake rupture segmentation along the HSS over millennial timescales.
    Keywords: 551.22 ; subduction seismogenesis ; GPS ; locking degree ; fault interactions ; earthquake rupture segmentation
    Language: English
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  • 12
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    Temporal Modulation of the Local Microseism in the North Sea (2021)
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    Publication Date: 2021-10-12
    Description: Primary and secondary microseism originating in the world oceans and peaking at around 14 and 7 s, respectively, characterize the Earth's background noise in that frequency range. Microseism generated in marginal seas with partly shorter periods and higher spatial and temporal variability is less studied and requires stations in immediate proximity to the source to be observed. Such studies can help to elucidate the exact microseism generation areas and mechanisms in a constrained area. We analyze 15 years of broadband data recorded at the seismic station on Helgoland island in the marginal North Sea. In addition to remote primary (RPM) and secondary microseism (RSM) originating in the North Atlantic, we observe strong and dominant local secondary microseism (LSM) with on average higher frequencies above 0.2 Hz, in accordance with shorter wave periods of about 4–8 s in the shallow North Sea. During times with low RSM activity we observe local primary microseism (LPM) at frequencies in agreement with local ocean wave periods. The higher horizontal to vertical (H/V) ratio of LPM with respect to LSM indicates a major non-Rayleigh wave contribution. LSM and LPM show a strong modulation with local semidiurnal ocean tides and microseism energy maxima preceding the water level maximum by 2.5 and 1.5 hr, respectively. This time shift might be influenced by stronger currents during rising than falling tides. Active sources of tide-modulated microseism migrate along the North Sea coast in sync with the ocean tidal signal as evidenced by comparison of LSM maxima at stations distributed along the coast.
    Keywords: 551.22 ; ocean microseism ; seismic noise ; seismic noise sources ; ocean tides
    Language: English
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  • 13
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    Delayed and Sustained Remote Triggering of Small Earthquakes in the San Jacinto Fault Region by the 2014 Mw 7.2 Papanoa, Mexico Earthquake (2021)
    Details
    Publication Date: 2021-09-03
    Description: We apply a move max matched-filter method to detect heightened seismicity triggered in the San Jacinto fault (SJF) zone, by the 2014 Mw 7.2 Papanoa, Mexico earthquake. The move max matched filter detects 5.4 and 1.7 times the number of earthquakes in the Southern California Seismic Network catalog and those detected by the matched-filter method, respectively. The seismicity rate increases significantly ~3.5 hr after the passage of the teleseismic waves and persists above the background level for about 1 week. This observation of delayed triggering may imply that dynamic stresses had initiated a time-dependent advance to failure or a secondary process. A highly active triggered patch is located ~10 km west of the SJF near Anza, on a previously unmapped fault. Focal mechanisms and a best fit plane suggest a normal fault perpendicular to the SJF. The unmapped fault may indicate higher seismic hazard in the surrounding areas if a large earthquake nucleated around the Anza seismic gap.
    Keywords: 551.22 ; 557 ; Southern California ; San Jacinto Fault ; triggering ; move max matched-filter ; unmapped fault ; Anza gap
    Language: English
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  • 14
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    Erdbebenstationen und Seismogramme in Deutschland seit 1898 (2021)
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    Publication Date: 2021-09-03
    Description: research
    Keywords: 551.22 ; seismogram ; earthquake ; FID-GEO-DE-7
    Language: German , English
    Type: presentation
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  • 15
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    Applying Conservation of Energy to Estimate Earthquake Frequencies from Strain Rates and Stresses (2021)
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    Publication Date: 2021-10-06
    Description: Estimating earthquake occurrence rates from the accumulation rate of seismic moment is an established tool of seismic hazard analysis. We propose an alternative, fault-agnostic approach based on the conservation of energy: the Energy-Conserving Seismicity Framework (ENCOS). Working in energy space has the advantage that the radiated energy is a better predictor of the damage potential of earthquake waves than the seismic moment release. In a region, ENCOS balances the stationary power available to cause earthquakes with the long-term seismic energy release represented by the energy-frequency distribution's first moment. Accumulation and release are connected through the average seismic efficiency, by which we mean the fraction of released energy that is converted into seismic waves. Besides measuring earthquakes in energy, ENCOS differs from moment balance essentially in that the energy accumulation rate depends on the total stress in addition to the strain rate tensor. To validate ENCOS, we exemplarily model the energy-frequency distribution around Southern California. We estimate the energy accumulation rate due to tectonic loading assuming poroelasticity and hydrostasis. Using data from the World Stress Map and assuming the frictional limit to estimate the stress tensor, we obtain a power of 0.8 GW. The uncertainty range, 0.3–2.0 GW, originates mainly from the thickness of the seismogenic crust, the friction coefficient on preexisting faults, and models of Global Positioning System (GPS) derived strain rates. Based on a Gutenberg-Richter magnitude-frequency distribution, this power can be distributed over a range of energies consistent with historical earthquake rates and reasonable bounds on the seismic efficiency.
    Keywords: 551.22 ; conservation of energy ; linear poroelasticity ; seismicity model ; Southern California
    Language: English
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  • 16
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    Low-Frequency Seismicity at Villarrica Volcano: Source Location and Seismic Velocities (2021)
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    Publication Date: 2021-10-01
    Description: Villarrica Volcano (Chile) is one of the most active volcanoes in South America. Its low-frequency (≤5 Hz) seismicity consists of a continuous tremor, overlain by impulsive transient events of higher amplitude in 60-s intervals. This signal was recorded in March 2012 by an extensive local network, comprising 75 stations and including 6 subarrays. It allowed us to apply and compare three techniques to locate the origin of the seismicity: intersection of propagation directions determined by array analysis, mapping amplitudes, and modeling of amplitude decay. All methods yield almost identical, temporally stable, epicenters inside the summit crater, which confirms earlier attributions of the seismicity to volcanic activity inside the conduit. The discrete transients and the interevent tremor share the same source location. From the dominance of surface waves and the obvious scattering, we infer a source near the surface. For two arrays at the northern and western flank, a dispersion relation was derived, which allowed for the determination of S wave velocity-depth functions. At both locations, the velocity structure can be modeled by three layers with interfaces at 100 and 400m depths. The velocities (300 to 3,000 m/s) correspond to pyroclastic material at different states of consolidation. The modeling of the amplitude decay reveals a quality factor around 50.
    Keywords: 551.22 ; volcano seismology ; beamforming ; amplitude decay ; source location ; scattering ; S wave velocity structure
    Language: English
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  • 17
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    Hyperspectral outcrop models for palaeoseismic studies (2021)
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    Publication Date: 2021-11-10
    Description: The traditional study of palaeoseismic trenches, involving logging, stratigraphic and structural interpretation, can be time consuming and affected by biases and inaccuracies. To overcome these limitations, a new workflow is presented that integrates infrared hyperspectral and photogrammetric data to support field-based palaeoseismic observations. As a case study, this method is applied on two palaeoseismic trenches excavated across a post-glacial fault scarp in northern Finnish Lapland. The hyperspectral imagery (HSI) is geometrically and radiometrically corrected, processed using established image processing algorithms and machine learning approaches, and co-registered to a structure-from-motion point cloud. HSI-enhanced virtual outcrop models are a useful complement to palaeoseismic field studies as they not only provide an intuitive visualisation of the outcrop and a versatile data archive, but also enable an unbiased assessment of the mineralogical composition of lithologic units and a semi-automatic delineation of contacts and deformational structures in a 3D virtual environment. Résumé L'étude traditionnelle des tranchées paléosismiques, impliquant l'enregistrement des coupes et l'interprétation stratigraphique et structurelle, peut prendre beaucoup de temps et être entachée de biais et d'inexactitudes. Pour surmonter ces limites, une nouvelle méthodologie est présentée, intégrant des données photogrammétriques et hyperspectrales infrarouges en appui aux observations paléosismiques de terrain. Comme étude de cas, cette méthode est appliquée à deux tranchées paléosismiques creusées à travers un escarpement de faille post-glaciaire dans le nord de la Laponie finlandaise. L'imagerie hyperspectrale (HSI) est corrigée géométriquement et radiométriquement, traitée à l'aide d'algorithmes classiques de traitement d'images et d'apprentissage machine, et recalée sur un nuage de points photogrammétrique. Les modèles virtuels d'affleurements améliorés par HSI constituent un complément utile aux études paléosismiques de terrain, car ils fournissent non seulement une visualisation intuitive de l'affleurement et une archive de données facile d'emploi, mais permettent également une évaluation non biaisée de la composition minéralogique d'unités lithologiques ainsi qu'une délimitation semi-automatique des contacts et des structures de déformation dans un environnement virtuel 3D.
    Keywords: 551.22 ; geology ; hyperspectral imaging ; outcrop models ; palaeoseismology ; remote sensing ; SfM photogrammetry
    Language: English
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