SCEC Award Number 18224 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Deriving Asperities from Fault Topography Data
Investigator(s)
Name Organization
Emily Brodsky University of California, Santa Cruz
Other Participants Kelian Dascher-Cousineau
SCEC Priorities 2d, 3a, 1d SCEC Groups FARM, Geology
Report Due Date 03/15/2019 Date Report Submitted 04/28/2019
Project Abstract
 Geometrical asperities play a key role in earthquake nucleation, rupture and seismic wave generation. In this project, we began to use measurements of exposed fault surfaces to infer a distribution of contact areas. We started to measure the distribution of continuous areas over various heights on actual fault surfaces. This distribution is not easily inferable from extant parameterizations of fault roughness. Early results suggest that in the isotropic regime at small scales, the asperity distribution on faults corresponds to a b-value of 1. We anticipate that the distribution of areas will be more easily translated to studies of seismological asperities than the previous treatment of faults.
Intellectual Merit Fault roughness has emerged as a central issue in earthquake physics. One of the most intriguing applications of roughness is to understanding asperities. Well-defined, persistent asperities are often invoked as a key element of earthquake physics, yet their physical origin remains elusive. Geometry is generally thought to be a key candidate for defining asperities. Here we attempt to specifically use measurements of fault surface roughness to define the asperity distribution in the natural system and compare it to the distributions expected for real faults.
Broader Impacts The magnitude distribution of earthquakes underlies all seismic hazard estimation. A better connection of the distribution to fundamental physics and geological observables would place the entire enterprise of seismic hazard assessment on firmer footing.
Exemplary Figure Figure 3 Island asperity distribution for hand sample of the Dixie Valley fault as measurement with a White Light Interferometer.