The aftershock signature of supershear earthquakes.
Recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks. This supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane. This shock wave may increase the destruction caused by the earthquake. We report that supershear earthquakes are characterized by a specific pattern of aftershocks: The fault plane itself is remarkably quiet whereas aftershocks cluster off the fault, on secondary structures that are activated by the supershear rupture. The post-earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments, whereas the activation of off-fault structures is explained by the shock wave radiation, which produces high stresses over a wide zone surrounding the fault.
Centre National de la Recherche Scientifique et Université Joseph Fourier, Grenoble, Laboratoire de Géophysique Interne et Tectonophysique, Boîte Postale 53, 38041 Grenoble, France. Michel.Bouchon@ujf-grenoble.fr
Michel
M
Bouchon
Hayrullah
H
Karabulut