[DLS] Eric Dunham (Stanford)

“Fault Valving, Slow Slip Events, and Earthquake Swarms in Seismic Cycle Models with Fault Zone Fluid Transport”

Seismic cycle modeling provides the framework to understand the fundamental processes driving the occurrence of earthquakes and aseismic slip, integrate experimental and observational constraints across a range of scales, and provide predictions relevant to earthquake physics and seismic hazard. These models capture time scales ranging from individual earthquake ruptures to thousands of years of slow loading and aseismic slip by simultaneously solving for the evolution of fault frictional strength, slip, and off-fault material deformation. In this talk, I will discuss our recent work to account for fault zone fluid transport in seismic cycle models. In subduction zones, fluids are sourced by metamorphic dehydration reactions in the subducting oceanic slab. Creep compaction at and below the seismogenic zone maintains near-lithostatic fluid pressure at depth, providing a pressure gradient in excess of hydrostatic that drives upward fluid flow. Fluid flux also depends on permeability, which dynamically evolves in response to fault slip and healing/sealing processes like mineral precipitation. Changes in pore pressure couple with slip by altering frictional strength. Our models show the emergence of fault valving events, manifesting as quasi-periodic pulses of high pore pressure, fluid flux, and aseismic slip that propagate upward into the base of the seismogenic zone. The events have recurrence intervals and slip/event that are similar to slow slip events in subduction zones. Pressure pulses ascending through the seismogenic zone trigger earthquake swarms as well as large ruptures. Our models provide the framework for interpreting and understanding the diverse spectrum of slip behaviors observed on natural faults.

EAPS Department Lecture Series
Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501.

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