National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2022

Numerical study on the characteristics of abyssal T-wave envelopes controlled by earthquake source parameters

Yun, S., W.S. Lee, R.P. Dziak, and H. Matsumoto

Seismol. Res. Lett., 93(4), 2189–2200, doi: 10.1785/0220210264, View online (2022)

Hydroacoustics has been successfully applied to detect and locate small‐to‐intermediate submarine tectonic activities infrequently recorded in land‐based seismic arrays. However, to extend the utilization of T waves to extract other important earthquake source parameters, such as source strength, the roles of earthquake focal mechanisms, and source depths in T‐wave envelopes must be thoroughly understood. We performed 3D numerical modeling considering anisotropic source radiation and realistic scattering in the oceanic crust for two focal mechanisms (normal and strike‐slip faults) and three depths (5, 10, and 15 km) to investigate the effect of source radiation and focal depth on abyssal T waves. By analyzing the synthetic T‐wave envelopes, we showed that stronger SV‐energy radiation from a normal‐fault earthquake event generates higher‐intensity T waves of the same source magnitude. The anisotropic source radiation of a double‐couple source causes azimuthal changes in the shapes of T waves, and deeper earthquakes cause gentle‐sloped envelopes; however, the slopes also vary with respect to the azimuths of receivers and focal mechanisms. Temporal changes in the slopes of T‐wave envelopes of magmatic swarm events near Wordie Volcano, Bransfield Strait, Antarctic Peninsula, imply that the depth dependency can be utilized to determine relative depths for hydrothermal‐vent events or sequenced earthquakes.

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