T-phase characterization of an oceanic transform fault earthquake swarm using the Ocean Observatories Cabled Array
Abstract
The Ocean Observatories Initiative Cabled Array incorporates 13 short-period and broadband seismic instruments on the Cascadia continental slop at Hydrate Ridge and near Axial Seamount on the Juan de Fuca Ridge. In addition to providing real-time geophysical data streams of local processes associated with volcanism and fluid flow, the Cabled Array also provides for improved monitoring of regional seismicity, including that associated with the subduction forearc and seismically active Blanco Transform Fault.
Seismic instrumentation associated with OOI seafloor cabled infrastructure went online in the Spring of 2015, a few months prior to a significant earthquake swarm on the western segment of the Blanco Transform Fault, approximately 150km south and 300km west of the Axial and Hydrate Ridge seismic arrays. In addition to recording seismic body and surface wave phases of this prolific earthquake sequence, many T-phases of presumably much smaller magnitude events were well-recorded by the seismic stations. This sequence involved several large earthquakes, including two M>5.8 events. In the hour following one M5.8 event, the ANSS catalog includes 6 earthquakes. During that same period T-phases from more than 20 smaller amplitude events were easily detected across all stations of the OOI network. Here, we explore characteristics of the T-phase-determined catalog of earthquakes, including temporal and spatial patterns of the earthquake swarm that occurred outside of the primary OOI seismic subarrays. We identify an empirical T-phase amplitude-earthquake magnitude relationship based on local magnitudes calculated from body waves, and consider challenges in distinguishing local events from far-field events using earthquake move-out times. We also use T-phase-detected events to explore temporal triggering patterns, which deviate from typical mainshock-aftershock patterns, potentially indicating distinctive stress triggering phenomena, as has been inferred on other oceanic transform faults.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS21E1613R
- Keywords:
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- 0545 Modeling;
- COMPUTATIONAL GEOPHYSICSDE: 4262 Ocean observing systems;
- OCEANOGRAPHY: GENERALDE: 4594 Instruments and techniques;
- OCEANOGRAPHY: PHYSICALDE: 7294 Seismic instruments and networks;
- SEISMOLOGY