← Back to Gallery

Characterizing Multi-Subevent Earthquakes Using the Brune Source Model

Brune source model has been widely used in ground motion prediction and source parameter estimation by describing the source process as a single pulse with a characteristic corner frequency. However, one pulse could be oversimplified for moderate to large earthquakes when 80% of Mw>5.5 earthquakes in the SCARDEC Source Time Functions Database are found to have multiple pulses that represent subevents in the rupture process (Danr et al., 2019).

Here we investigate the performance of Brune source model in characterizing complex earthquake sources. We first decompose source time functions in the SCARDEC database into summations of multiple Brune sources. Through the decomposition we obtain source parameters including the seismic moment, corner frequencies, and onset times of each subevent, such that we are able to compare subevents to the master events. We then select earthquakes identified with 2 subevents and explore the ranges of source parameters. We then build synthetic two-subevent source time functions varing source parameters accordingly. We generate synthetic waveforms of the two-subevent earthquakes and an empirical Green’s function using the Frequency-Wavenumber (FK) method. We fit the corner frequency of the master event using the spectral ratio method. In both SCARDEC database analysis and the synthetic test, the master event corner frequency is more related to the subevent with a larger seismic moment. We also find that the order of subevents matters, in which case the corner frequency of the master event is systematically higher when the larger subevent occurs first than when the smaller subevent occurs first.

Presenting Author: Meichen Liu

Student Presenter: Yes

Day: 4/21/2021

Time: 9:45 AM - 11:00 AM Pacific

Additional Authors