Junior Research Group of Dr. Rebecca Harrington: Physics of Earthquake Rupture
Using an observational approach, I investigate the differences between earthquake sources in different faulting environments. My current research focuses primarily on the following three questions: (1) What is the importance of tectonic regime for earthquake nucleation? (2) Are some types of unconventional seismic signals with complicated waveforms explained with simple seismic sources and complicated travel paths? (3) Does fault maturity change the dynamics of faulting?
I study the effect of tectonic regime on earthquake nucleation by investigating the occurrence of remote dynamic earthquake triggering. In efforts to constrain an earthquake triggering mechanism, I analyze both high quality waveform and catalog data. In my Ph.D. thesis work, I systematically show using a statistical approach to catalog data that long-range triggering does not occur in Japan at comparable levels to the western US and Greece. In addition, I analyze the filtered time series waveform files to search for occurrences of earthquakes missed by catalogs. The second and third perspectives from which I study the seismic source use the source time function obtained from seismic waveforms to calculate source parameters and examine source parameter relationships. Accurately calculating source parameters such as radiated energy, moment, and corner frequency requires removing path effects from seismograms. From one perspective, I am examining how path effects obscure source observations, making some seismograms appear unconventional. I find that path is primarily responsible for some of the unusual seismic signals seen in a volcanic environment, thereby eliminating a need for unnecessarily complicated earthquake source models.
In more standard faulting environments, I examine how fault maturity affects the dynamics of faulting. My most recent work carefully isolates earthquake populations on faults with different levels of maturity in the Parkfield, CA area, I investigate whether at least some variation in accepted values of source parameters results from combining global populations. In future work, I will investigate whether the differences in source parameters observed in Parkfield are generally present on mature faults. With new high quality data more readily available, I will investigate problems of source parameter scaling over wide ranges of magnitude, and investigations of self-similarity.