Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland

Handle URI:
http://hdl.handle.net/10754/555749
Title:
Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland
Authors:
Bethmann, F.; Deichmann, N.; Mai, Paul Martin ( 0000-0002-9744-4964 )
Abstract:
Theoretical considerations and empirical regressions show that, in the magnitude range between 3 and 5, local magnitude, ML, and moment magnitude, Mw, scale 1:1. Previous studies suggest that for smaller magnitudes this 1:1 scaling breaks down. However, the scatter between ML and Mw at small magnitudes is usually large and the resulting scaling relations are therefore uncertain. In an attempt to reduce these uncertainties, we first analyze the ML versus Mw relation based on 195 events, induced by the stimulation of a geothermal reservoir below the city of Basel, Switzerland. Values of ML range from 0.7 to 3.4. From these data we derive a scaling of ML ~ 1:5Mw over the given magnitude range. We then compare peak Wood-Anderson amplitudes to the low-frequency plateau of the displacement spectra for six sequences of similar earthquakes in Switzerland in the range of 0:5 ≤ ML ≤ 4:1. Because effects due to the radiation pattern and to the propagation path between source and receiver are nearly identical at a particular station for all events in a given sequence, the scatter in the data is substantially reduced. Again we obtain a scaling equivalent to ML ~ 1:5Mw. Based on simulations using synthetic source time functions for different magnitudes and Q values estimated from spectral ratios between downhole and surface recordings, we conclude that the observed scaling can be explained by attenuation and scattering along the path. Other effects that could explain the observed magnitude scaling, such as a possible systematic increase of stress drop or rupture velocity with moment magnitude, are masked by attenuation along the path.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Citation:
Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland 2011, 101 (2):515 Bulletin of the Seismological Society of America
Publisher:
Seismological Society of America (SSA)
Journal:
Bulletin of the Seismological Society of America
Issue Date:
22-Mar-2011
DOI:
10.1785/0120100179
Type:
Article
ISSN:
0037-1106
Additional Links:
http://www.bssaonline.org/cgi/doi/10.1785/0120100179
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Physical Sciences and Engineering (PSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorBethmann, F.en
dc.contributor.authorDeichmann, N.en
dc.contributor.authorMai, Paul Martinen
dc.date.accessioned2015-05-26T07:07:52Zen
dc.date.available2015-05-26T07:07:52Zen
dc.date.issued2011-03-22en
dc.identifier.citationScaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland 2011, 101 (2):515 Bulletin of the Seismological Society of Americaen
dc.identifier.issn0037-1106en
dc.identifier.doi10.1785/0120100179en
dc.identifier.urihttp://hdl.handle.net/10754/555749en
dc.description.abstractTheoretical considerations and empirical regressions show that, in the magnitude range between 3 and 5, local magnitude, ML, and moment magnitude, Mw, scale 1:1. Previous studies suggest that for smaller magnitudes this 1:1 scaling breaks down. However, the scatter between ML and Mw at small magnitudes is usually large and the resulting scaling relations are therefore uncertain. In an attempt to reduce these uncertainties, we first analyze the ML versus Mw relation based on 195 events, induced by the stimulation of a geothermal reservoir below the city of Basel, Switzerland. Values of ML range from 0.7 to 3.4. From these data we derive a scaling of ML ~ 1:5Mw over the given magnitude range. We then compare peak Wood-Anderson amplitudes to the low-frequency plateau of the displacement spectra for six sequences of similar earthquakes in Switzerland in the range of 0:5 ≤ ML ≤ 4:1. Because effects due to the radiation pattern and to the propagation path between source and receiver are nearly identical at a particular station for all events in a given sequence, the scatter in the data is substantially reduced. Again we obtain a scaling equivalent to ML ~ 1:5Mw. Based on simulations using synthetic source time functions for different magnitudes and Q values estimated from spectral ratios between downhole and surface recordings, we conclude that the observed scaling can be explained by attenuation and scattering along the path. Other effects that could explain the observed magnitude scaling, such as a possible systematic increase of stress drop or rupture velocity with moment magnitude, are masked by attenuation along the path.en
dc.publisherSeismological Society of America (SSA)en
dc.relation.urlhttp://www.bssaonline.org/cgi/doi/10.1785/0120100179en
dc.rightsArchived with thanks to Bulletin of the Seismological Society of America © 2015 by the Seismological Society of Americaen
dc.titleScaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerlanden
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalBulletin of the Seismological Society of Americaen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionSwiss Seismological Service Institute of Geophysics ETH Zurich, NO H39.2, Sonneggstrasse 5 CH-8092 Zurich, Switzerlanden
kaust.authorMai, Paul Martinen
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