Distinguishing the Coseismic Phase of the Earthquake Cycle with Seismogeodesy

Session: Earthquake Source Parameters: Theory, Observations and Interpretations
Type: Oral
Date: 4/30/2020
Time: 02:30 PM
Room: 120 + 130
Description: 

Inversions for earthquake source and fault slip distribution models rely on reliable static surface displacements from GNSS stations. Recent studies have demonstrated the utility of peak-ground-displacement in rapid magnitude estimation. Determination of these crucial parameters requires the choice of an appropriate time window for the displacement time series. It is important to determine the most accurate earthquake time span, individually at each station, in order to avoid overestimating the coseismic moment by including early postseismic motion. In addition, it is necessary to account for different durations of seismic shaking due to site characteristics, path, and directivity effects. Most studies have considered the time span of the coseismic phase based on daily GNSS displacements. Others use regional seismic instruments to determine the start of seismic shaking but choose the time interval to be constant for all GNSS stations regardless of their hypocentral distance, geological setting, or azimuth relative to fault rupture. Here we calculate a measure of energy at seismic stations to properly bracket the earthquake period. We then interpolate these times to all GNSS stations in the area and differentiate between the earthquake’s coseismic and early postseismic motion. After we determine the relevant earthquake time interval at each station, we can reliably extract useful information regarding the earthquake source. We apply our method to a set of earthquakes in California and Japan and find substantial differences with existing methods. 

Presenting Author: Dorian Golriz

Authors