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Apparent stress variations near the Osa Peninsula, Costa Rica, influenced by subducted bathymetric features
Author(s) -
Moyer Pamela A.,
Bilek Susan L.,
Phillips W. Scott
Publication year - 2011
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 - 10.1029/2010gl045955
Subject(s) - geology , aftershock , seismology , subduction , bathymetry , peninsula , thrust fault , tectonics , oceanography , history , archaeology
We compute apparent stress for 114 aftershocks (0.9 ≤ M L ≤ 3.7) of the 1999 M w = 6.9 Quepos, Costa Rica, thrust‐faulting earthquake to examine the influence of subducting plate topographic complexity near the Osa Peninsula on earthquake rupture. Using seismic coda techniques, we find a heterogeneous distribution in apparent stress of 0.1–2.5 MPa (mean 0.6 MPa) for these aftershocks. Mean aftershock apparent stress is more than twice the global mean for thrust‐faulting earthquakes at oceanic subduction zones and 1.5 times the mean for events just northward along the margin near the Nicoya Peninsula where the subducting plate has lower relief. We also find constant source scaling for the Osa aftershocks. The variation in apparent stress found near the Osa Peninsula, and high mean as compared to global and regional values, suggest areas of stress concentration in the region of bathymetric complexity in the subduction zone.