Primary source characteristics of the 2022 Sichuan Luding Ms6. 8 Earthquake

An M(s)6. 8 earthquake struck Luding, a county in Sichuan Province on September 5, 2022. We collected the phase data of the regional seismograph network, the seismic broadband P waveform data from the Global Seismic Network (GSN), the Federal Digital Seismic Networks (FDSN) and the GEOFON Network of the German Research Centre for Geosciences, and quickly analyzed the primary source characteristics of this earthquake by using techniques of the doubledifference relocation, the centroid moment tensor inversion, the finite-fault waveform inversion, and the apparent source time function (ASTF) analysis. From the relocation, the aftershocks were distributed in style of swarms. Three swarms were clustered around the epicenter, and about 30 km northwestern and southeastern, respectively. Generally, the events in northwest were shallower than those in southeast. The centroid moment tensor inversion indicated that the centroid was at 29. 55 degrees N,102. 14 degrees E and at depth of 16 km, a scalar moment of 1. 0068 X 10(19)N center dot m was released, yielding a magnitude of M-W 6. 6o, the double-couple component was 88%, and it was an approximately pure strike-slip event. Considering the spatial feature of the aftershock distribution, we concluded that this event occurred on a fault plane of strike 163 degrees, dip 77 degrees (dipping to southwest), rake -5 degrees. The finite-fault inversion showed that the rupture area was composed of two patches, with one around the initial point, which is the main part, whereas the other being more southeastern, and generally the rupture appeared to be unilateral from northwest to southeast, with a maximum slip of 1. 4 m near the initial point. As the centroid moment tensor inversion and the finite-fault inversion showed, the whole duration time was about 20 s, and clearly, the energy was released in two periods. Deduced from the azimuthal dependence of the ASTFs, the predominant rupture direction was in azimuth of similar to 165 degrees, which is consistent with the faulting strike, and the estimate of scalar seismic moment based on the averaged ASTF was almost identical with what was solved by the finite-fault inversion, and also very close to what was solved by the centroid moment tensor inversion.

Automated summary

An M(s)6.8 earthquake occurred in Luding, Sichuan Province on September 5, 2022. The analysis of phase data and waveform data revealed that the aftershocks were clustered around the epicenter and distributed in swarms. The source characteristics indicated a pure strike-slip event with a rupture area composed of two patches and a maximum slip of 1.4 m near the initial point. The whole duration time was about 20 s and the energy was released in two periods. The predominant rupture direction was consistent with the faulting strike.