Burst-Type Repeating Earthquakes as a Proxy for Transient Aseismic Slip

Session: Waveform Cross-Correlation-Based Methods in Observational Seismology
Type: Oral
Date: 4/30/2020
Time: 08:30 AM
Room: 230 + 235
Description: 

Continuously operating Global Positional System (cGPS) networks have enabled the detection of slow slip events (SSEs) at subduction margins and continental transform boundaries. However, offshore shallow SSEs in subduction zones and relatively small or deep continental strike-slip SSEs are often out of the range of cGPS land networks. This observational limitation may be improved using related secondary seismicity, such as tremor, to infer the location of SSEs. Tremor is likely comprised of repeating low frequency earthquakes (LFEs) caused by repeated rupture of small seismic asperities. Similarly, repeating earthquakes, or repeaters, are sequences of events with nearly identical waveforms thought to involve repeated rupture of the same fault asperity, or short-distance triggering of closely spaced asperities, driven to failure by aseismic slip on the surrounding fault. “Burst-type” repeaters are concentrated in time, have short and irregular repeat intervals, variable magnitudes (indicating rupture of nearby asperities) and are observed during aftershock sequences and afterslip (i.e., transient aseismic slip). We argue that sequences of burst-type repeaters are similar to LFEs that comprise tremor and can likewise be used to detect and locate transient aseismic slip. Using template matching and land and ocean bottom seismic data, we identify burst-type repeaters associated with known slow slip events at the northern Hikurangi Subduction Margin, New Zealand and at the Anza segment of the strike-slip San Jacinto fault, southern California. These findings indicate that burst-type repeaters are a reliable proxy for transient aseismic slip. This is particularly important for determining the full interplay of seismic and aseismic slip in areas that are not tremorgenic or well-instrumented geodetically.

Presenting Author: Heather R. Shaddox

Authors