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Fault‐perpendicular aftershock clusters following the 2003 Mw = 5.0 Big Bear, California, earthquake
Author(s) -
Chi WuCheng,
Hauksson Egill
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 - 10.1029/2005gl025033
Subject(s) - aftershock , seismology , geology , perpendicular , rake , slip (aerodynamics) , perturbation (astronomy) , fault (geology) , geodesy , geometry , physics , geomorphology , mathematics , quantum mechanics , thermodynamics
To explore aftershock‐triggering mechanisms for the 2003 Big Bear, California earthquake sequence, we determined differential travel‐times and applied the double‐difference technique to relocate these events, which formed three clusters. The main cluster coincides with the 3 km long northwest striking sub‐vertical mainshock fault. The other two sub‐vertical clusters, located at opposite ends of the mainshock rupture, are almost perpendicular to the mainshock fault, contradicting the 60° separation angle of conjugate faults as predicted from frictional laws. Allowing for a 30° uncertainty in the cataloged strike, dip and rake values about 75% of the aftershocks are strike‐slip as determined from first motion and complete waveform moment tensor inversions. We use a mainshock conceptual slip model to derive Coulomb Failure Stress regions, and assess correlations between stress increases and aftershock locations. We conclude that the perpendicular aftershock clusters were triggered by the mainshock static stress perturbation.