CORRELATIONS OF STRESS DISTRIBUTIONS ALONGTHE FAULT: FROM LABORATORY FRACTUREROUGHNESS TO FAULT ASPERITY SQUEEZE

摘要

We analyze the spatial correlations of the absolute stress field along the Nojimafault, Japan in terms of scaling invariance (self-affine scaling). Despite thesmall range of resolution, we obtain a signature of correlations consistent withan elastic compression of the fault roughness. Indeed, we compare the waveletspectrum of the measured stress field to that obtained from a numerical modelthat fully squeezes two thick elastic media bounded by interfaces which includespatially correlated asperities (i.e. non diluted asperities). Friction is assumed tofollow a Coulomb law locally and interface roughness is described using the self-affine topography that is observed over a very wide range of scales from fracturesto faults, with a Hurst exponent H. We find that the stress field is also self-affine,but with a Hurst exponent H — 1. Fluctuations of the normal stress are shown tobe important, especially at local scales with anti-persistent correlations.