The spatial distribution of earthquake stress rotations following large subduction zone earthquakes

Abstract

Rotations of the principal stress axes due to great subduction zone earthquakes have been used to infer low differential stress and near-complete stress drop. The spatial distribution of coseismic and postseismic stress rotation as a function of depth and along-strike distance is explored for three recent M ≥ 8.8 subduction megathrust earthquakes. In the down-dip direction, the largest coseismic stress rotations are found just above the Moho depth of the overriding plate. This zone has been identified as hosting large patches of large slip in great earthquakes, based on the lack of high-frequency radiated energy. The large continuous slip patches may facilitate near-complete stress drop. There is seismological evidence for high fluid pressures in the subducted slab around the Moho depth of the overriding plate, suggesting low differential stress levels in this zone due to high fluid pressure, also facilitating stress rotations. The coseismic stress rotations have similar along-strike extent as the mainshock rupture. Postseismic stress rotations tend to occur in the same locations as the coseismic stress rotations, probably due to the very low remaining differential stress following the near-complete coseismic stress drop. The spatial complexity of the observed stress changes suggests that an analytical solution for finding the differential stress from the coseismic stress rotation may be overly simplistic, and that modeling of the full spatial distribution of the mainshock static stress changes is necessary.

Cyclical variations of fluid sources and stress state in a shallow megathrust-zone mélange

“…6a), similar to the ambient conditions of shallow active subduction megathrusts as imaged by geophysical methods (e.g. Saffer and Tobin 2011;Hardebeck 2017). Given the very low differential stress that can be sustained by the thrust based on its mode of failure, it is reasonable that even a modest coseismic drop in shear stress would cause a long-term postseismic rotation of σ 1 (e.g.…”

The World Stress Map database release 2016: Crustal stress pattern across scales

“…Another challenge is to capture temporal stress changes and horizontal stress tensor rotations which are observed at various scales. For example, at the tectonic plate boundaries the stress changes occur due to tectonic loading in the inter-seismic phase and from stress drops of major earthquakes (Hardebeck, 2017). Here the rapid increase of data from satellite geodesy in data density and length of high-quality timeseries provide potential to detect temporal stress changes (Heidbach and Ben-Avraham, 2007;Kreemer et al, 2014;Townend and Zoback, 2006).…”

“…Knowledge of the in-situ stress is also essential for the understanding of geodynamic processes such as global plate tectonics and earthquakes (Hardebeck, 2017;Harris, 1998;King et al, 1994;Richardson, 1992;Scholz, 1998;Steinberger et al, 2001; as well as to mitigate induced seismicity (Hakimhashemi et al, 2014b;Gaucher et al, 2015;Segall and Fitzgerald, 1998;Zang et al, 2013). The stress evolution during the seismic cycle is one of the key processes that define the maturity of active faults and controls nucleation, rupture propagation and arrest of an earthquake (Hardebeck and Okada, 2018;Hergert and Heidbach, 2011;Oglesby and Mai, 2012;Schorlemmer and Wiemer, 2005;Stein, 1999).…”

Crustal dynamics: unified understanding of geodynamic processes at different time and length scales

“…Hardebeck (2017) investigated coseismic and postseismic rotations of principal stress axes caused by three M > 8.8 subduction megathrust ruptures. The largest coseismic stress rotations occur just above the Moho depth of the overriding plate where large continuous slip patches appear (from seismological studies) to coincide with areas of intense fluid overpressuring inferred to promote near-complete shear stress drop.…”