Site Specific Coseismic Time Window using Seismogeodesy and the Extraction of Earthquake Source Parameters
Dorian Golriz
Scripps Institution of Oceanography
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Summary
In the first part of this talk, I will present a new method to determine the earthquake’s coseismic time window using a combination of seismic and GNSS data. Current practice is to use daily GNSS positioning for static offsets determination and finite slip models. When using high-rate (1-5 Hz) GNSS positioning for this purpose, it is a common practice to take a single time window across all the affected stations (typically a few minutes). Since the postseismic phase starts immediately after the earthquake, in a continuous manner, these static offsets include early postseismic deformation that occurs minutes to hours after the earthquake. Here I show the differences between these offset estimates, and how they can affect coseismic slip models. In the second part the talk, I will show how we can use this coseismic time window to estimate earthquake magnitude for tsunami warning purposes. The Pacific Tsunami Warning Center (PTWC) uses 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 using a Kalman filter yields both broadband velocity and displacement waveforms that do not clip and are sensitive to the entire spectrum of ground motions. We can use this combination to rapidly determine earthquake magnitude. Replaying seismogeodetic data for a number of tsunamigenic earthquakes around the Pacific basin, we show that useful and reliable estimates can be obtained before the end of rupture. Additionally, our method does not rely on empirical relationships derived from historical earthquakes, making it suitable for local tsunami warning systems and shows promise for earthquake early warning.
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