Towards Understanding the Range of Fault Properties that Generate Tremor and Earthquake Activity Along the San Andreas Fault

Sumy Danielle F, Palisades NY

Investigators

Abstract

Dr. Danielle F. Sumy has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the US Geological Survey, Pasadena. This study will investigate the spatial and temporal distribution of earthquake and tremor activity along the Parkfield - Cholame segment of the San Andreas Fault. Tremor, a long duration low-frequency seismic signal, occurs at deeper depths than traditional earthquake activity and can illuminate the transition between the shallow, earthquake generating portions of the fault and the deeper stable-sliding regime. She will first locate earthquake and tremor signals from seismic waveform data recorded by the temporary Parkfield Experiment to Record MIcroseismicity and Tremor (PERMIT) array. The PERMIT array consists of thirteen densely-spaced seismometers centered directly over the zone of tremor activity, and augments existing seismic networks in this area. Accurate locations of earthquake and tremor activity will allow for an assessment of how much deformation is accommodated via tremor versus earthquake activity. Finally, these results will allow for a detailed investigation into the relationship between tremor and earthquakes, and whether tremor has a part in nucleating earthquake activity or vice versa. The aim of the experiment is to advance our understanding of how the shallow and deeper portions of the San Andreas Fault communicate with one another, and to shed light on the range of fault properties that generate earthquake and tremor activity at this site. Since the first observations of tremor made almost a decade ago, the conditions necessary to generate tremor activity, and whether earthquakes and tremor are generated by the same processes, is hotly debated. Through this research, the entire range of fault behaviors from the earthquake-generating to silently-slipping portions of the San Andreas Fault, as well as the conditions necessary to generate and trigger earthquake and/or tremor activity, will be better understood. Outreach and educational activities associated with this research involve introducing the Quake-Catcher Network (QCN) to K-12 schools and teacher workshops. The QCN is widely distributing seismic sensors throughout K-12 schools and the general public to engage students in scientific research by directly involving them in data collection and interpretation. Additionally, her own research into the relationship between earthquakes and tremor will be introduced through an activity named "Earthquake Science Through Sound". As part of the activity, the entire spectrum of seismic activity from regular earthquakes to tremor to silent earthquakes will be introduced through musical instruments and through the conversion of seismograms to sound.