GOUGE - Hydrothermal deformation experiments on ICDP fault zone materials

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Fault gouge from seismogenic zone drilling may shed light on earthquake mechanisms and thus, indirectly help to assess societal risk. ICDP recovered such materials in compressional (Chelungpu, Taiwan), strike-slip (San Andreas, USA) and extensional systems (Gulf of Corinth, Greece). In this proposal, we suggest the development of a heated (up to 200-250°C), back-pressured direct shear apparatus where such fault gouges may be tested at up to 200 MPa normal stress. It will offer a wide range of opportunities to precisely measure rate-dependent frictional strength of sediments and rocks, transients of pore pressure and permeability during loading, failure, and shear movement, and dilatancy versus shear-enhanced compaction and strengthening at the known or inferred in situ conditions. The major focus will be the SAFOD project, as new core is recovered at this moment. It will be complemented by material from the Nobeaka and Nojima faults, rocks from the Shimanto Belt or the Franciscan Complex (to cover a wide temperature spectrum going as high as ca. 350°C), and exhumed rocks from slab break-off on Crete (also a potential ICDP drill site). As a mid-term perspective, the results can be compared to important marine equivalents such as major decollement gouges at the Nankai Trough (to be recovered within IODP with DV Chikyu) and elsewhere, and hence link the two scientific drilling programs in the continental and marine realm.