Publication Date:
2023-02-09
Description:
Static stress transfer from major earthquakes is commonly invoked as the primary mechanism
for triggering aftershocks, but evaluating this mechanism depends on aftershock rupture plane orientations
and hypocenter locations, which are often subject to significant observational uncertainty. We evaluate static
stress change for an unusually large data set comprising hundreds to thousands of aftershocks following the
1997 Umbria-Marche, 2009 L’Aquila (Italy), and 2019 Ridgecrest (California) earthquake sequences. We
compare failure stress resolved on aftershock focal mechanism planes and planes that are optimally oriented
(OOPs) in the regional and earthquake perturbed stress field. Like previous studies, we find that failure stress
resolved on OOPs overpredicts the percentage (〉70%) of triggered aftershocks relative to that predicted from
observed aftershock rupture planes (∼50%–65%) from focal mechanisms solutions, independent of how nodal
plane ambiguity is resolved. Further, observed aftershock nodal planes appear statistically different from
OOPs. Observed rupture planes, at least for larger magnitude events (M 〉 3), appear to align more closely with
pre-existing tectonic structures. The inferred observational uncertainty associated with nodal plane ambiguity,
plane orientation, and, to second order, hypocentral location yields a broad range of aftershocks potentially
triggered by static stress changes, ranging from slightly better than random chance to nearly any aftershock
promoted, particularly those further than 5 km from the causative fault. Dynamic stresses, afterslip, pore fluids,
and other sources of unresolved small-scale heterogeneity in the post-mainshock stress field may also contribute appreciably to aftershock occurrence closer to the mainshock
Description:
Published
Description:
e2021JB023589
Description:
3T. Fisica dei terremoti e Sorgente Sismica
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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