Observations of the 22 July 2020 Mw 7.8 Simeonof earthquake from small-aperture seismic arrays in Alaska

Abstract:

We examine the feasibility and merit of utilizing seismic array analysis as a routine tool for detecting and analyzing seismic events in and around Alaska. Alaska has three minor seismic arrays (each with five elements) and one major array (20 elements). These arrays provide high signal-to-noise records suitable for beamforming at regional and teleseismic distances. Our goal is to investigate ways of extracting additional data for major earthquake sequences and explore key aspects of the implementation of array processing at these scales.

The 22 July 2020 Simeonof earthquake on the Alaska-Aleutian subduction zone is the first M>7 earthquake since the Alaska Earthquake Center began running event detections on array data in real-time. In this study we (1) examine the performance of our seismic array analysis, and (2) explore the effects of having real-time back-azimuth and slowness parameters for characterizing the rupture dimensions and directivity of the mainshock.

In addition, by analyzing a hand-curated catalog of regional-scale earthquakes that are well-recorded on the four seismic arrays, we compare between different algorithms and processing parameters, as well as the variation in array designs. These events provide a large dataset that spans backazimuths, depths, distances, magnitudes, and event types thus allowing for statistically robust comparisons.