Publication Date:
2017-06-03
Description:
To understand the seismogenic potential of shallow plate-boundary thrust faults (décollements) in relatively warm subduction zones, water-saturated Na-montmorillonite gouges were sheared at a pore fluid pressure of 10 MPa, effective normal stresses (σn eff) of 10–70 MPa, temperatures (T) of 25–150°C, and axial displacement rates of 0.03–3 μm/s. The Na-montmorillonite gouges were frictionally very weak at all conditions tested (steady state friction coefficient μss = 0.05–0.09). At T ≤ 60°C, Na-montmorillonite showed a transition from velocity-strengthening to velocity-weakening behavior with increasing σn eff, whereas at T ≥ 90°C it was largely velocity neutral or velocity strengthening, irrespective of σn eff. The rates of frictional healing (β) showed extremely low values (mostly 〈0.001) at all temperatures. Our results suggest that the existence of Na-montmorillonite in the décollement zone at Costa Rica and Nankai promotes aseismic slip, particularly at shallow depths, forming weakly coupled regions. ©2017. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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