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Nontrivial decay of aftershock density with distance in Southern California
Author(s) -
Moradpour Javad,
Hainzl Sebastian,
Davidsen Jörn
Publication year - 2014
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2014jb010940
Subject(s) - aftershock , exponent , seismology , magnitude (astronomy) , geology , crust , shock (circulatory) , scale (ratio) , power law , anisotropy , geodesy , physics , astrophysics , geophysics , mathematics , statistics , optics , medicine , linguistics , philosophy , quantum mechanics
The decay of the aftershock density with distance plays an important role in the discussion of the dominant underlying cause of earthquake triggering. Here, we provide evidence that its form is more complicated than typically assumed and that in particular a transition in the power law decay occurs at length scales comparable to the thickness of the crust. This is supported by an analysis of a very recent high‐resolution catalog for Southern California (SC) and surrogate catalogs generated by the Epidemic‐Type Aftershock Sequence (ETAS) model, which take into account inhomogeneous background activity, short‐term aftershock incompleteness, anisotropic triggering, and variations in the observational magnitude threshold. Our findings indicate specifically that the asymptotic decay in the aftershock density with distance is characterized by an exponent larger than 2, which is much bigger than the observed exponent of approximately 1.35 observed for shorter distances ranging from the main shock rupture length up to a length scale comparable to the thickness of the crust. This has also important consequences for time‐dependent seismic hazard assessment based on the ETAS model.