Određivanje i interpretacija spektara magnitude potresa

Magnitude spectra are determined for three major earthquakes of the year 1985: the Xianjiang earthquake of 23 August, and the Mexico earthquake of 19 September with its largest aftershock of 21 September. Broad-band recordings obtained at the Central Seismological Observatory of the Federal Republic of Germany (GRF) are used for the analysis. Pass-band seismograms are obtained by way of filtering the broad-band seismogram. The magnitude spectrum of an earthquake is determined from the velocity amplitude for each Fourier component. The magnitude spectrum represents the velocity amplitude density spectrum at the earthquake source scaled in magnitude units. A comparison of the magnitude spectra shows significant differences between the focal parameters of the earthquakes, even if their conventional magnitudes (m b , M s ) are similar

Collecting macroseismic data in Germany by internet – an overview

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_ch12lectur

Introduction: Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard: New Insights and Suggested Procedures

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-3865Introduction to DGEB-Publikation Nr. 18 Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik (DGEB)editoria

Seismological stations and seismograms in Germany since 1898

researc

Relationship between magnitude, macroseismic intensity and distance for induced earthquakes in Germany

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.researc

Anwendung des Ausschlusskriteriums „Seismische Aktivität“ bei der Suche und Auswahl eines Standorts für ein Endlager für hochradioaktive Abfälle in Deutschland

Im Standortauswahlgesetz wird in § 22 zum Ausschlusskriterium „Seismische Aktivität“ ausgeführt, dass ein Gebiet nicht als Endlagerstandort geeignet ist, wenn die örtliche seismische Gefährdung größer als in Erdbebenzone 1 nach DIN EN 1998-1/NA:2011-01 ist. Diese Norm wird in Kürze durch eine Aktualisierung ersetzt, die dem Stand von Wissenschaft und Technik entspricht. Der Entwurf hierzu, E DIN EN 1998-1/NA:2018-10, enthält keine Zuordnungen in Erdbebenzonen mehr, sondern weist die seismische Gefährdung räumlich kontinuierlich aus. Die Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) hat im Auftrag der Bundesgesellschaft für Endlagerung einen Vorschlag zur Anwendung dieses Ausschlusskriteriums unter Verwendung von E DIN EN1998-1/NA:2018-10 erarbeitet. Die BGR schlägt vor, als Grenzwert zur Anwendung des Ausschlusskriteriums den Wert der spektralen Antwortbeschleunigung im Plateaubereich von 1,8 ms-2 in E DIN EN 1998-1/NA:2018-10 zu verwenden. Dieser Wert entspricht der makroseismischen Intensität 7, für den die seismische Gefährdung größer als in Erdbebenzone 1 nach DIN EN 1998-1/NA:2011-01 ist. Für Gebiete, in denen dieser Wert überschritten wird, gilt das Ausschlusskriterium als erfüllt. Grundsätzlich ist das Ausschlusskriterium „Seismische Aktivität“ im Standortauswahlgesetz jedoch wenig geeignet, um die Erdbebengefährdung eines Standortes für ein Endlager für hochradioaktive Abfälle zu ermitteln. Der Bewertungszeitraum für die Sicherheit des Endlagers beträgt eine Million Jahre und unterscheidet sich erheblich vom Betrachtungszeitraum von 50 Jahren der Norm DIN EN 1998-1/NA. Die Intensität bzw. die Beschleunigung gilt für die Erdoberfläche; die Endlagerung hochradioaktiver Abfälle soll jedoch in tiefen geologischen Formationen erfolgen. Neben der Gefährdung aufgrund von seismischen Bodenbewegungen als Bewertungsmaßstab des Ausschlusskriteriums hat eine andere Art der Gefährdung durch Erdbeben für Endlager in tiefen geologischen Formationen eine größere Bedeutung, nämlich bruchartige Verschiebungen im Endlagerbereich. Das Ausschlusskriterium „Seismische Aktivität“ bezieht sich im Unterschied zu allen anderen Ausschlusskriterien im Standortauswahlgesetz § 22 nicht auf ein wissenschaftlich formuliertes Merkmal, sondern auf eine Norm, deren Bemessungsgrößen aufgrund eines Kompromisses zwischen Sicherheitsbetrachtungen und wirtschaftlichen Überlegungen wie erhöhten Baukosten festgelegt wurden.poste

Earthquake Database of Germany

Earthquake Database of Germany Diethelm Kaiser, Gernot Hartmann Federal Institute for Geosciences and Natural Resources, Hannover, Germany The earthquake catalogue for Germany (Leydecker 2011) was integrated in the earthquake database GERSEIS of BGR. For this purpose, the database was extended and a browser based application was developed to improve the database access (Kaiser et al. 2014). The following requirements in terms of structure and functionality were considered: tracking of event parameter changes, archive of erroneously inserted events (fakes, misinterpretations), schemes of relationships among the references and sources for an event, macroseismic data points, prioritization of epicentres, magnitudes and intensities, synchronization with catalogues from other institutions. The parameters of 12,667 seismic events for the years 800 to 2008 have been integrated. 6,861 of these events could be associated to events already existing in GERSEIS. In the course of integration seismological parameters have been reviewed, they have been corrected or complemented for 68 earthquakes. The database GERSEIS now contains instrumental and macroseismic parameters of more than 43,000 earthquakes since the year 800 until today. For approximately 38,000 events at least one instrumental magnitude is available, mostly local magnitude ML. Homogenously determined ML (BGR/SZGRF) are available since 1995 for 11,000 earthquakes. For 6,700 earthquakes macroseismic parameters are available, mostly epicentral intensity which is the most common parameter for earthquakes older than 1970. The database contains isoseismal radii for 1100 earthquakes, 150 of these have isoseismal radii of intensity 5 and larger. The database GERSEIS is accessible as web map service (WMS) through the BGR Product-center https://produktcenter.bgr.de and by interactive query, map display, and data download through the BGR Geoviewer https://geoviewer.bgr.de. We plan to improve the earthquake database by re-evaluating important historical earthquakes, building a macroseismic database, and determining moment magnitudes from instrumental and macroseismic data. References Kaiser, D., Bürk, D., Hartmann, G., Stelling, U. & Schlote, H. (2014): Integration of catalogues of historical and instrumentally recorded earthquakes in Germany in a common database – Concepts, uses, and products. Second European Conference on Earthquake Engineering and Seismology (2ECEES); Istanbul, http://www.eaee.org/Media/Default/2ECCES/2ecces_esc/3202.pdf. Leydecker, G. (2011): Erdbebenkatalog für Deutschland mit Randgebieten für die Jahre 800 bis 2008. Geologisches Jahrbuch, E 59, 1-198.https://www.bgr.bund.de/DE/Themen/Erdbeben-Gefaehrdungsanalysen/Veranstaltungen/HistEarth_Paleoseis_Okt2017/histEarth_paleoseis_2017_node.htmlpresentatio

Relationships to Estimate the Magnitude Ms of Historical Earthquakes in Europe from Macroseismic Observations

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.poste

P-wave magnitude spectra, stress drops, rupture complexities and other source parameters from broadband seismograms of three 1987 Southern California earthquakes.

Three large earthquakes in Southern California – the Whittier Narrows earthquake of 1 October 1987 (WN), and the Elmore Ranch (ER) and Superstition Hills (SH) earthquakes of 24 November 1987 are analyzed using broadband recordings from the Graefenberg (GRF) array. The P-wave seismograms from all stations of the array are utilized to determine the magnitude spectra of the earthquakes. The magnitude spectrum represents the velocity amplitude density spectrum at the earthquake source, scaled in magnitude units. At 1 Hz the magnitude spectra show good agreement with the NEIC mb (5.8, 5.7, and 6.0 respectively for events WN, ER, and SH). The maximum magnitudes, however, occur at longer periods (16 s, 4.1 s, and 3.6 for WN, ER, and SH) and have larger values (6.3, 6.6, and 6.7 for WN, ER, and SH). Other source parameters determined from magnitude spectra are P-wave energy, seismic moment, fault length, average stress drop, and source complexity. The magnitude spectra and the source parameters show systematic variations across the stations of the GRF array. These variations are interpreted as the effect of changes in the local geological conditions underneath the array. The variations are smallest for the maximum spectral magnitude (with a standard deviation of less than 1%) and the largest for the stress drop (average standard deviation of 40%). Additional source parameters derived from the magnitude spectra are: asperity radius, displacement across the asperity, localized stress drop, and ambient faulting stress. Significant differences in the magnitude spectra and source parameters are observed between ER and SH on one side and WN on the other. The magnitude spectra of ER and SH are much simpler in shape, as compared to WN, which in turn is characterized by a high complexity and a low average stress drop (0.1 MPa). ER appears to be the result of a smooth and simple rupture with a homogeneous stress drop. SH reveals a moderate rupture complexity