Open Access
Signature of transition to supershear rupture speed in the coseismic off-fault damage zone
Author(s) -
Jorge Jara,
Lucile Bruhat,
Marion Y. Thomas,
Solène Antoine,
Kurama Okubo,
Esteban Rougier,
Ares J. Rosakis,
Charles G. Sammis,
Y. Klinger,
Romain Jolivet,
Harsha S. Bhat
Publication year - 2021
Publication title -
proceedings - royal society. mathematical, physical and engineering sciences
Language(s) - English
Resource type - Journals
eISSN - 1471-2946
pISSN - 1364-5021
DOI - 10.1098/rspa.2021.0364
Subject(s) - transition zone , aftershock , seismology , geology , fault (geology) , signature (topology) , shear (geology) , wave speed , shear zone , geophysics , mechanics , physics , petrology , geometry , tectonics , mathematics
Most earthquake ruptures propagate at speeds below the shear wave velocity within the crust, but in some rare cases, ruptures reach supershear speeds. The physics underlying the transition of natural subshear earthquakes to supershear ones is currently not fully understood. Most observational studies of supershear earthquakes have focused on determining which fault segments sustain fully grown supershear ruptures. Experimentally cross-validated numerical models have identified some of the key ingredients required to trigger a transition to supershear speed. However, the conditions for such a transition in nature are still unclear, including the precise location of this transition. In this work, we provide theoretical and numerical insights to identify the precise location of such a transition in nature. We use fracture mechanics arguments with multiple numerical models to identify the signature of supershear transition in coseismic off-fault damage. We then cross-validate this signature with high-resolution observations of fault zone width and early aftershock distributions. We confirm that the location of the transition from subshear to supershear speed is characterized by a decrease in the width of the coseismic off-fault damage zone. We thus help refine the precise location of such a transition for natural supershear earthquakes.