169 Advances and Challenges in Seismotectonic Studies in Slow-Deforming Regions

This session explores advances and challenges in understanding tectonic deformation in slow-deforming regions, integrating geodetic, geological, and modeling approaches to address earthquake hazards in seemingly stable yet vulnerable intraplate settings.

Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 217D

Influence of back-arc mantle strength on far-field postseismic deformation: Insights from the 2011 Tohoku-Oki earthquake and the Korean Peninsula

Paper number: 169-4
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Stress transfer between faults caused by seismic events has triggered aftershocks and subsequent earthquakes. The Mw 9.0 Tohoku-Oki earthquake on March 11, 2011, near the coast of eastern Japan, increased seismic activity within the intraplate faults of the Eurasian Plate. Since 2011, the Korean Peninsula, located over 1200 km from the epicenter, has experienced microearthquakes and several moderate earthquakes (M > 5). Geodetic, seismological, and geophysical investigations have demonstrated that the great earthquake induced static and quasi-static stress changes in faults within the Korean Peninsula. Viscoelastic relaxation of the rheological structure occurred in response to earthquake-induced stress perturbations over a wide upper mantle for several decades. Postseismic viscoelastic deformation has been identified as a dominant factor in intraplate fault stress changes in previous numerical models. However, the laterally homogeneous layered structure model representing the Eurasian Plate neglects the effects of viscoelastic behavior due to the rheological contrast between the ~1000 km wide back-arc and the continent. The back-arc mantle of the East Sea (Japan Sea), which was extended until ~12 Ma, exhibits a thickness difference of more than 30 km compared to the Korean Peninsula, indicating weakened rheological strength due to mantle uplift. We conducted a three-dimensional numerical model incorporating the Pacific Plate, Philippine Sea Plate, and Eurasian Plate, including back-arc mantle heterogeneity. Our study examines the remote stress transfer between interplate and intraplate faults caused by the extended back-arc mantle in the subduction zone.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412066

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