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Authors: Caporali, A.* 
Barba, S.* 
Carafa, M. M. C.* 
Devoti, R.* 
Pietrantonio, G.* 
Riguzzi, F.* 
Title: Static stress drop as determined from geodetic strain rates and statistical seismicity
Issue Date: 2010
DOI: 10.1029/2010JB007671
Keywords: earthquakes
seismic hazard
Subject Classification04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes 
04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology 
04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations 
04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring 
04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones 
Abstract: Two critical items in the energetic budget of a seismic province are the strain rate, which is measured geodetically on the Earth’s surface, and the yearly number of earthquakes exceeding a given magnitude. Our study is based on one of the most complete and recent seismic catalogs of Italian earthquakes and on the strain rate map implied by a multi-year velocity solution for permanent GPS stations. For 36 homogeneous seismic zones, we used the appropriate Gutenberg Richter relation based on the seismicity catalog to estimate a seismic strain rate, which is the strain rate associated with the mechanical work due to a co-seismic displacement. The volume storing most of the elastic energy is associated with the long-term deformation of each seismic zone, and therefore, the seismic strain rate is inversely proportional to the static stress drop. The GPS-derived strain rate for each seismic zone limits the corresponding seismic strain rate, and an upper bound for the average stress drop is estimated. These results demonstrated that the implied regional static stress drop ranged from 0.1 to 5.7 MPa for catalog earthquakes in the moment magnitude range [4.5–7.3]. These results for stress drop are independent of the “a” and “b” regional parameters and heat flow but are very sensitive to the assumed maximum magnitude of a seismic province. The data do not rule out the hypothesis that the stress drop positively correlates with the time elapsed after the largest earthquake recorded in each seismic zone.
Description: Accepted for publication in Journal of Geophysical Researches. Copyright (2010) American Geophysical Union
Appears in Collections:Papers Published / Papers in press

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