Slow Slip and Sporadic Seismicity
Joan Gomberg
USGS
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Summary
Fault slip is a primary mode of relaxing strain energy that builds in 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.