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Date: 4/20/2021

Session Time: 4:15 PM to 5:15 PM Pacific

Effects and Uses of Aseismic Deformation and Fault Creep in Seismic Hazard and Warning

While earthquake hazard increases with fault area and slip, the hazard can relate to the extent of aseismic deformation. For instance the down-dip extent of intermediate and large earthquakes is limited by ductile deformation. The rate strengthening rheology provides a dynamic barrier to propagation during the earthquake, and a static barrier by relaxing down-dip stress during the interseismic period. The along strike extent of rupture can also be limited by fault rheology and by long-term aseismic deformation producing a relaxed region, e.g., the creeping section of the San Andreas.

Aseismic deformation and fault creep can also correlate in time and space with seismic slip, such as in regions of low seismic coupling. Volcanoes, regions of induced seismicity and subduction zones often have low coupling coefficients yet host significant seismicity. For example, small scale seismicity can be generated by larger scale aseismic fault creep, allowing the seismicity to be used as a proxy for slip. In instances of accelerating aseismic deformation, such seismicity may have value for warning. At larger scale, the subduction zone foreshocks and transient creep events that preceded the great Tohoku earthquake, were perhaps related to megathrust earthquake initiation, and may also be useful for warning. Underlying all of these observations are poorly known physics dictated by the rheology. The strongest rheological constraints may come from the observations themselves, but the physics are most easily determined in experiments or in models.

We invite a broad range of contributions that illustrate the value of including aseismic deformation and fault creep in earthquake hazard and warning. While context is provided by the above examples, these are not comprehensive. Contributions are expected from earthquake science disciplines that provide observations, constraints or implications, e.g., seismology, geodesy, fault mechanics, numerical modeling, experimental rock mechanics.

Conveners

Nicholas Beeler, U.S. Geological Survey (nbeeler@usgs.gov)
Amanda Thomas, University of Oregon (amt.seismo@gmail.com)
Manoochehr Shirzaei, Virginia Tech (shirzaei@vt.edu)

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