S030-0006
Signature of supershear transition in natural earthquakes

Thursday, 10 December 2020
Poster
Harsha Bhat1, Jorge Jara2, Lucile Bruhat3, Solène Antoine4, Kurama Okubo5, Marion Y Thomas1, Esteban Rougier6, Ares Rosakis7, Yann Klinger8, Romain Jolivet9 and Charles G Sammis10, (1)CNRS, Paris Cedex 16, France, (2)Ecole Normale Supérieure, PSL Université, CNRS UMR 8538, Laboratoire de Géologie, Paris, France, (3)Ecole Normale Superieure Paris, Paris, France, (4)Ecole Normale Supérieure de Paris, Paris, France, (5)Harvard University, Earth and Planetary Sciences, Cambridge, MA, United States, (6)Los Alamos National Laboratory, EES-17, Los Alamos, NM, United States, (7)California Institute of Technology, Graduate Aerospace Laboratories, Pasadena, CA, United States, (8)Institut de Physique du Globe de Paris, Paris, France, (9)Ecole Normale Supérieure, PSL Research University, CNRS UMR 8538, Laboratoire de Géologie, Paris, France, (10)Univ Southern California, Los Angeles, CA, United States
Abstract:
Supershear earthquakes are rare but powerful ruptures with devastating consequences. Traditionally, studies of supershear earthquakes have focused on determining which fault segments sustained fully-grown supershear ruptures. But the rarity of such events, combined with the fact that conditions for supershear are still debated, complicates the investigation of supershear transition in real earthquakes. The details of the transition, including its location, are then often overlooked. Here, we propose a unique signature of the location of a supershear transition. We combine theoretical fracture mechanics, and numerical modeling of off-fault coseismic damage, with high-resolution field observations of fault damage and aftershock distribution, to show that the location of the transition from subshear to supershear speeds can be pinpointed by a localized absence of aftershocks, and a decrease in off-fault damage, due to a transient reduction of the stress intensity at the rupture tip.
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