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Earthquake recurrence models fail when earthquakes fail to reset the stress field

Geophysical Research Letters

By:
, ,
DOI: 10.1029/2012GL052913

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Abstract

Parkfield's regularly occurring M6 mainshocks, about every 25 years, have over two decades stoked seismologists' hopes to successfully predict an earthquake of significant size. However, with the longest known inter-event time of 38 years, the latest M6 in the series (28 Sep 2004) did not conform to any of the applied forecast models, questioning once more the predictability of earthquakes in general. Our study investigates the spatial pattern of b-values along the Parkfield segment through the seismic cycle and documents a stably stressed structure. The forecasted rate of M6 earthquakes based on Parkfield's microseismicity b-values corresponds well to observed rates. We interpret the observed b-value stability in terms of the evolution of the stress field in that area: the M6 Parkfield earthquakes do not fully unload the stress on the fault, explaining why time recurrent models fail. We present the 1989 M6.9 Loma Prieta earthquake as counter example, which did release a significant portion of the stress along its fault segment and yields a substantial change in b-values.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Earthquake recurrence models fail when earthquakes fail to reset the stress field
Series title:
Geophysical Research Letters
DOI:
10.1029/2012GL052913
Volume
39
Issue:
18
Year Published:
2012
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Earthquake Hazards Program
Description:
L18310
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters