Extreme dynamic weakening of faults during dehydration by coseismic shear heating

Takehiro Hirose (1) , Misha Bystricky (2)

1 INGV - Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Roma
2 LMTG - Laboratoire des Mécanismes et Transfert en Géologie

The dynamic strength of seismogenic faults has a critical effect on earthquake slip instability and seismic energy release. High velocity friction experiments on simulated faults in serpentinite at earthquake slip conditions show a decrease in friction coefficient from 0.6 to 0.15 as the slip velocity reaches 1.1 m/s at normal stresses up to 24.5 MPa. The extraordinary reduction in fault strength is attributed to flash heating at asperity contacts of gouge particles formed during sliding. The rapid heating at asperities causes serpentine dehydration. In impermeable fault zones in nature, serpentine dehydration and subsequent fluid pressurization due to coseismic frictional heating may promote further weakening. This dynamic fault-weakening mechanism may explain the lack of pronounced heat flow in major crustal faults such as the San Andreas.

Mots clés: Seismology: Earthquake dynamics (1242); Structural Geology: Fractures and faults; Tectonophysics: Dynamics and mechanics of faulting (8004); Tectonophysics: Rheology and friction of fault zones (8034)

Domaines: Sciences de la Terre

Takehiro Hirose, Misha Bystricky. Extreme dynamic weakening of faults during dehydration by coseismic shear heating. Geophysical Research Letters, 2007, 34, pp.14311. ⟨10.1029/2007GL030049⟩. ⟨hal-00320113⟩