Earth’s free surface complicates inference of absolute stress from earthquake-Induced stress rotations

Geophysical Research Letters
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Abstract

The stress redistribution from an earthquake can produce localized measurable rotations of the principal stress axes if the absolute level of differential stress in the crust in on the order of the earthquake stress drop. Two simple analytic solutions have been developed to estimate the differential stress from an observed stress rotation. However, each has assumptions that may not be accurate near Earth’s free surface. I model synthetic earthquakes in an elastic half-space, and show that the assumptions of the methods are accurate for strike-slip earthquakes, and for deep dip-slip earthquakes. However, they are incorrect for shallow dip-slip earthquakes. I introduce a free surface correction for one of the methods for dip-slip earthquakes. I revise an analysis of stress rotations due to great subduction zone earthquakes, including this correction. The results support the original conclusion of near complete stress drop for many shallow subduction zone earthquakes.
Publication type Article
Publication Subtype Journal Article
Title Earth’s free surface complicates inference of absolute stress from earthquake-Induced stress rotations
Series title Geophysical Research Letters
DOI 10.1029/2023GL106574
Volume 51
Issue 4
Year Published 2024
Language English
Publisher AGU
Contributing office(s) Earthquake Science Center
Description e2023GL106574, 8 p.
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