Group A, Poster #061, Seismology

Real-Time Seismogeodetic Earthquake Magnitude Estimates for Local Tsunami Warnings

Dorian Golriz, Barry Hirshorn, Yehuda Bock, Stuart Weinstein, & Jonathan R. Weiss
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Poster Presentation

2022 SCEC Annual Meeting, Poster #061, SCEC Contribution #12524 VIEW PDF
Tsunami Warning Centers (TWCs) use a variety of tools to issue a tsunami warning based on the size and location of the earthquake. However, current methods that rely on seismic data alone suffer from magnitude saturation or not timely enough for coastal communities located closest to the earthquake’s rupture. The combination of GNSS and strong-motion data (seismogeodesy) yields both broadband velocity and displacement waveforms that do not clip and are sensitive to the entire spectrum of ground motions. We estimate a seismogeodetic earthquake moment magnitude from collocated GNSS and seismic stations that are within 20 to 700 km epicentral distance for nine 7.2 < Mw < 9.1 earthquakes. ...We consider the vertical component of seismogeodetic displacement as an approximate source time function and integrate the associated time series to obtain the seismic moment. By continuing to integrate vertical displacement beyond the initial P waves, we obtain rapid estimates of Mw that are within 0.2 magnitude units for 8 thrust faulting events and within 0.3 units for the single normal faulting event. Because our estimates of the seismic moment are based on the maximum value of integrated displacement, no regression against other source parameters, or distance, is necessary. Results indicate that our new method is promising for earthquake and local tsunami early warning systems, including tsunami earthquakes characterized by relatively slow moment release over a longer rupture time, as well as for earthquakes with a complex source time function.