SZ4D International Webinars: Slow slip in subduction zones - Do deformation fabrics and and laboratory experiments explain instrumental observation?
Onno Oncken - Helmholtz-Zentrum Potsdam, GFZ; Telegrafenberg, D-14473 Potsdam, Germany
January 22nd, 2021 at 9 AM PST
Cataclasites are a characteristic rock type in drilled active as well as exposed fossil subduction faults. They exhibit evidence for pervasive pressure solution and abundant hydrofracturing. Slip velocities associated with the formation of the different types of cataclasites and conditions controlling slip are so far poorly constrained. Here, we explore exposed sections of subduction faults and their microstructures and apply recently proposed constitutive laws to compare predicted deformation rates with instrumental observations from subduction zones. Basic arguments are derived from estimating the maximum strain rates using fault scaling relationships, and comparing these with rates predicted from experimental flow laws for cataclastic flow. The prevailing pore pressure ratio and state of elastic loading during the seismic cycle turn out to be the controlling parameters linking the variety of rock fabric observations with instrumentally recorded slip velocities governing transient creep episodes.
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