Frictional Characteristics of Oceanic Transform Faults: Progressive Deformation and Alteration Controls Seismic Style

Abstract

Oceanic transform faults have low seismic coupling, and display far fewer and smaller earthquakes than expected from fault length-magnitude scaling relations, based on the Harvard centroid moment tensor catalog (e.g., Bird et al., 2002). Instead, up to 95% of displacement occurs aseismically, despite the faults cross-cutting the brittle mafic crust (Boettcher & Jordan, 2004). This earthquake deficit has been explained in two ways: (a) oceanic transforms experience both earthquakes and aseismic creep along the same fault segments, but at different times (e.g., Abercrombie & Ekström, 2001;Hilley et al., 2020;McGuire et al., 1996); and/or (b) oceanic transforms are segmented into "locked patches" hosting quasi-periodic earthquakes of Mw > 6.0, and microseismically active "rupture barriers" dominated by creep (e.g.

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