A Meso-Scale Take on the Modeling of Fault Zone Faulting Behaviors

Date: 4/24/2019

Time: 03:00 PM

Room: Cascade II

From strike-slip fault cores to subductions “interfaces” exhibiting rotated blocks, breccia, (silt, clay) deformation bands, those dilatant/contractant places where aseismic slip, slow-slip and seismic slip occur are far from simple. Locating each type of event is hard work, but examples are showing up where seismic and aseismic events are not just neighbors (hinting at triggering relationships) but may actually be collocated.

It seems important, in this context, to look at larger spectrum alternatives to purely frictional models that focus on thin interfaces, where (a-b) values need to be chosen, prescribing to a large extent whether the local behavior will be seismic or aseismic.

We propose that mesoscale empirical/conceptual fault core models that can be calibrated from geophysical data, are used to lead to new insights. Such a model was applied to oceanic transform faults and we are presenting here a generic study on the conditions that can lead to/from SSE to/from seismic. The model includes an original poro-plastic hardening/softening standard interface constitutive law with an end cap criterion, as well as a (currently simple) structural model that approximates the various scales involved in geological faults. It spontaneously produces contractant or dilatant behavior of fault areas at a large range of time scales from seconds to days to years, as a function of absolute stress magnitude, tectonic loading and fluid compressibility. Current results show that zones generating SSE and seismogenic areas are not mutually exclusive and a whole continuum of behaviors can happen on the same fault, including in short succession, depending namely on fault maturity, current deformation regime and on-going fluid conditions.

Case studies are needed to calibrate the model parameters and check the model predictions against monitoring data. For more realistic simulations, the interface model could be plugged into 2D or 3D crustal fault or subduction interface models.

Presenting Author: Delphine D. Fitzenz

Authors