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Examining the Distribution of Earthquakes Within the Alaska-Aleutian Subduction Zone Using Events Detected by the Alaska Amphibious Community Seismic Experiment

Description: 

Small earthquakes in subduction zones indicate where deformation is taking place and can help us understand why regions exhibit differences in plate coupling and rupture behavior; however, knowledge of precise earthquake locations relative to large-scale structure is critical for interpretations. Between May 2018 and September 2019, the Alaska Amphibious Community Seismic Experiment (AACSE) deployed 30 land stations and 75 ocean-bottom seismometers (OBS) within the Alaska-Aleutian Subduction Zone (AASZ). The AACSE array in combination with the nearby Earthscope Transportable Array and permanent stations led to the detection of over 7,200 earthquakes. These events were located using the same parameters the Alaska Earthquake Center routinely uses for events detected on their permanent array of land stations. The routine catalog placed many events in the general vicinity of the interplate thrust zone, indicating activity on that fault, but large depth uncertainties allow for other interpretations. In particular, many of these earthquakes may be within the downgoing plate as has been observed farther east in the 1964 rupture zone. Inspection of travel times to OBSs directly above earthquakes confirms that the apparent thrust-zone earthquakes lie well below the plate interface, showing deformation within the downgoing plate. An additional 15,000 events have been detected within the AACSE dataset using EQTransformer trained on the AACSE land data. To better understand the distribution of earthquakes within the AASZ, we conducted a joint velocity-hypocenter inversion to relocate all the events detected by the AACSE array. A 3D velocity model and station corrections are used in the inversion to account for the complex sedimentary structure beneath the OBSs. This catalog in combination with one being developed between the end of AACSE in October 2019 and the July 22, 2020 Mw 7.8 Simeonof earthquake (see Friedman-Alvarez et al., this session) will help improve our understanding of how the distribution of earthquakes relates to subduction zone structure and seismic cycles.

Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Sarah

Student Presenter: Yes

Invited Presentation: 

Authors