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Response of the San Jacinto Fault Zone to static stress changes from the 1992 Landers earthquake
Author(s) -
Bhloscaidh Mairéad Nic,
McCloskey John,
Bean Christopher J.
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 - 10.1002/2014jb011164
Subject(s) - aftershock , induced seismicity , coulomb , seismology , geology , stress (linguistics) , fault (geology) , magnitude (astronomy) , exponential function , geodesy , statistical physics , physics , mathematics , mathematical analysis , astrophysics , nuclear physics , linguistics , philosophy , electron
We perform an analysis of the seismicity response of the San Jacinto Fault Zone to static Coulomb stress changes from the 1992 Landers earthquake sequence. Results show that, in general, stress changes forecast rate changes well: we find a significant positive correlation between the change in rate and the magnitude of the Coulomb stress change, with a correlation coefficient of ρ = 0.76 (equivalent to 5.6 σ , when compared to a ρ = 0 null hypothesis). Furthermore, although the correlations are less clear over negative than positive stress changes, there is evidence of some Coulomb stress dependent quiescence on stress shadows. Models that account for heterogeneity in reference seismicity show clear improvements in their predictions of spatial variability of aftershock rates, compared to those that assume uniform reference. We find also that better performance is obtained (1) using a time‐dependent Coulomb Rate‐State model compared to a time‐independent exponential model and (2) using structurally constrained rather than optimal target fault orientations. These results are an important step in the validation of Coulomb stress based methods for quantitative seismicity forecasting. We conclude that the correspondence between the predictions of Coulomb stress models for aftershock seismicity may be sensitive to strong heterogeneity in aftershock locations and orientations associated with the presence of large‐scale structure in aftershock study areas. In these cases, we suggest that, where the regional structure is mapped, incorporating it explicitly into Coulomb stress models may improve the performance of quantitative Coulomb stress‐based forecasts.