Polytechnic University of Valencia Congress, 1st Congress in Geomatics Engineering

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STRESS TRANSFERE AND STATISTICAL ANALYSIS OF 2012 AHAR-VARZEGHAN SEISMIC SEQUNCE, NORTHWESTERN IRAN
Pouye Yazdi, Jorge Miguel Gaspar Escribano, Miguel Angel Santoyo

Last modified: 18-10-2017

Abstract


In 11 of August 2012, two destructive earthquakes with Mw= 6.4 and 6.2 occurred between cities Ahar and Varzeghan (Northwest Iran). They had a close epicentral distance of 6 Km and also had a short time lag of 11 minutes. Following that, a high-rate of aftershock activity began where during the first month more than 2000 events (M≥0.7) affected several villages in the area. The seismic released energy induced significant damage and losses in an extensive zone. Right after the seismic doublet occurrence, a surface rupture with a primarily east-west orientation was observed. The idea of having an almost vertically dipped fault plane for the first shock is more consistent with the trace of the upper edge on the surface and the focal mechanism solutions which propose a steady dipping EW. Previous studies propose different geometries for the generating faults of the second earthquake. In this study, we associate the surface rupture with the first mainshock and both nodal plane explaining the relationship between the two main seismic events are discussed after Coulomb failure stress calculation due to the first shock. Then the stress transfer because of the doublet is analyzed in order to determine its consistency with the statistical modeling prediction for the aftershock population and spatial distribution. For statistical modeling a temporal version of Epidemic Type Aftershock Sequence (ETAS) is applied on one-year seismicity including events with minimum magnitude of 2.5.

http://dx.doi.org/10.4995/CIGeo2017.2017.6662


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