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New insights into the mechanism of postseismic stress relaxation exemplified by the 23 June 2001 M w = 8.4 earthquake in southern Peru
Author(s) -
Hergert Tobias,
Heidbach Oliver
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024858
Subject(s) - geology , viscoelasticity , seismology , crust , stress relaxation , standard linear solid model , rheology , creep , subduction , relaxation (psychology) , geodesy , mantle (geology) , stress (linguistics) , geophysics , tectonics , physics , psychology , social psychology , linguistics , philosophy , thermodynamics
The 2001 M w = 8.4 southern Peru subduction earthquake marked the beginning of a transient postseismic surface motion in direction of the coseismic displacement at the permanent GPS station Arequipa. In general this motion is assigned to afterslip. Our hypothesis is that the observed transient signal can be explained by stress relaxation processes in the overriding plate. We use a 2D finite element model incorporating non‐linear viscoelastic Maxwell rheology. Our model results indicate that coseismically induced stresses are relieved by viscoelastic stress relaxation in the lower crust. The trenchward directed creep motion is transferred to the upper crust due to elastic coupling leading there to an instantaneous relief of elastic stresses. In contrast to the existing conceptual models for stress relaxation, which incorporate shear stresses, we conclude that tensional elastic stresses throughout the crust and upper mantle are the main driving forces for the transient GPS signal.