Demonstrating the Utility of Seafloor Geodetic Instrumentation: A Case Study of the Simeonof-Sand Point-Chignik Earthquake Sequence Along the Alaska Subduction Zone
Global Navigation Satellite System-Acoustic (GNSS-Acoustic) is a seafloor geodetic technique that combines acoustic ranging between the sea surface platform (typically an autonomous Wave Glider) and seafloor transponders with standard GNSS positioning to locate points on the seafloor to cm-level horizontal accuracy. GNSS-Acoustic is a powerful tool to measure horizontal seafloor offsets of subduction zones resulting from earthquakes such as the 2020-2021 earthquake sequence along the Shumagin segment of the Alaska subduction zone, including the 22 July 2020 Mw7.8 Simeonof, the 19 October 2020 Mw7.6 Sand Point and the 28 July 2021 Mw8.2 Chignik earthquakes. The proximity of these earthquakes to established GNSS-Acoustic sites presents a rare opportunity to add geodetic constraints on slip estimations from the seaward side of the earthquakes. In the months following each of the earthquakes, we deployed a GNSS-Acoustic Wave Glider to the nearest of three GNSS-Acoustic sites, which allowed us to measure the permanent seafloor offset trenchward of each earthquake. We present these GNSS-Acoustic position time series as well as fault slip models enhanced by the availability of these seafloor geodetic data. With the added GNSS-Acoustic data, we are able to infer shallow slip in the Simeonof and Chignik earthquakes not previously resolved with a kinematic inversion using only the sparse regional continuous GNSS and strong-motion accelerometer sensors installed on the nearby Aleutian Islands. We hope these results serve as a practical demonstration of how even minimal seafloor geodetic observations near the trench of a subduction zone can enhance our resolution of subduction zone behavior and motivate the further offshore instrumentation of subduction zones.
Session: Seismo-geodetic Approaches for Seismic and Tectonic Processes
Type: Oral
Room: Regency E-G
Date: 4/21/2022
Presentation Time: 02:15 PM Pacific
Presenting Author: John DeSanto
Student Presenter: No
Additional Authors
John DeSanto Presenting Author Corresponding Author jdesanto@uw.edu University of Washington |
Benjamin Brooks bbrooks@usgs.gov U.S. Geological Survey |
Brendan Crowell crowellb@uw.edu University of Washington |
Todd Ericksen tericksen@usgs.gov U.S. Geological Survey |
Dara Goldberg degoldberg@usgs.gov U.S. Geological Survey |
Scott Nooner nooners@uncw.edu University of North Carolina |
David Schmidt dasc@uw.edu University of Washington |
Spahr Webb scw@ldeo.columbia.edu Columbia University |
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Demonstrating the Utility of Seafloor Geodetic Instrumentation: A Case Study of the Simeonof-Sand Point-Chignik Earthquake Sequence Along the Alaska Subduction Zone
Category
Seismo-geodetic Approaches for Seismic and Tectonic Processes
Description