Title: Slow Slip and Sporadic Seismicity
Joan Gomberg, Dash Fitzgerald, Kathryn Materna, Aaron Wech
Abstract:
Fault slip is a primary mode of relaxing strain energy that builds in the Earth due to plate motions and other deformation changes. Considerable evidence indicates that fault slip proceeds erratically, both during ‘fast’, seismic-wave producing earthquakes and during ‘slow’, transient, largely aseismic slippages (slow slip events, SSEs). While distinct earthquakes may be clearly delineated, such delineation is not as straightforward for SSEs. This irregularity and scaling of slip impact the amplitudes and frequencies of any seismic radiation (waves or shaking), and thus the hazard associated with these slip events. Although the links between earthquake slip and seismicity have been relatively well established, they remain conjectural for SSEs; a commonly assumed hypothesis proposes SSEs trigger very small seismic events that relax negligible strain energy but provide valuable proxies of the slow slip that initiates them. These seismically recorded proxies may reveal details of the evolving slow slip not resolvable with today’s geodetic data. We attempt to test this proxy hypothesis and make inferences about the irregularity and scales of slip during SSEs using both seismic and geodetic observations. We focus on observations of seismic tremor in the subduction zone of Cascadia and earthquake swarms in the transform plate boundary region of southern California.
Biography: Joan Gomberg is a research geophysicist with the US Geological Survey (USGS), specializing in earthquake seismology for the USGS Earthquake Hazards. Her research focuses on earthquake interactions, initiation, and fault slip, as well as related studies of volcano and landslide processes. She leads and participates in the USGS’s activities that advance subduction zone science, particularly in Cascadia, within the USGS and with partners nationally and internationally. The latter have included a broad range of projects, in Mexico, Panama, Russia, India, Italy, Ireland, France, New Zealand, Japan, and most recently Costa Rica. Joan also leads and participates in regional education and outreach activities. She is a Fellow of the American Geophysical Union, participates in the Subduction Zones in 4-Dimensions Initiative and the Cascadia Regional Earthquake Science Center, is a member of the Seismological Society of America, and an affiliate professor at the University of Washington, Seattle. Prior to moving to Seattle in 2006, Joan worked for 12 years in the USGS’s office in Memphis, Tennessee. She received her PhD in geophysics from University of California, San Diego and her BS from the Massachusetts Institute of Technology.
Contact: gomberg@usgs.gov