The researchers propose to generate comprehensive models of the unusual April 4th, 2010 Mw 7.2 Sierra El Mayor-Â‐‑Cucapah earthquake in northern Baja California. A number of novel observations were made of this earthquake?s behavior, including multiple mapped stepovers between ruptured fault segments, eyewitness reports of locally reversed rupture direction, plus the earthquake had a greater rupture length (~100 km) than is typically seen for an event of its size. We will model the event in two ways: first, with a kinematic inverse model that incorporates all available observational data (e.g. InSAR, GPS, teleseismic waveforms, strong motion waveforms, geologic rupture data) in order to generate both realistic subsurface geometries of the fault segments involved, and a picture of how the slip evolved on those faults during the earthquake rupture. This will be achieved using a Bayesian maximum likelihood-Â‐‑based method developed by the PI. Second, they will produce forward dynamic earthquake rupture models using a 3D finite element code that seek to reproduce the features seen in the kinematic model and by eyewitnesses, by varying the initial physical conditions (e.g. pre-Â‐‑earthquake stresses and frictional conditions.) The end result will be a full description of both how and why the earthquake ruptured. The incorporation of such a diverse range of expertise into a single earthquake study has not been attempted before.
We stand to gain more insights into the earthquake process than would be possible from applying any of the individual techniques in isolation. In addition, a detailed description of the faulting involved in the earthquake will help us to evaluate its potential effects on the nearby active faults in southern California ? the Elsinore and San Jacinto faults, and thus aid seismic hazard assessments in the region. In addition to disseminating findings through conferences and publications, the researchers aim to communicate our findings to the public by developing museum exhibits in both English and Spanish for display at UC Riverside and elsewhere.