Evidence of Nonlinear Elasticity of the Crust from the Mw7.6 Manyi (Tibet) Earthquake.

Satellite synthetic aperture radar (SAR) interferometry shows that the magnitude 7.6 Manyi earthquake of 8 November 1997 produced a 170-kilometer-long surface break with up to 7 meters of left-lateral slip, reactivating a N76 degrees E quaternary fault in western Tibet. The radar interferometric map reveals asymmetric, along-strike displacement profiles between the two sides of the surface rupture, a pattern that cannot be explained with linear elastic theory. This observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth. A model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry, a ratio that is consistent with laboratory and borehole measurements.

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