Evaluating Seismicity Patterns in Western China

Yingying Zhang, & Walter D. Mooney

Submitted August 15, 2019, SCEC Contribution #9766, 2019 SCEC Annual Meeting Poster #181

Ebel and Chambers (2016) found that some modern M ≥ 4.0 earthquakes in California and Nevada preferentially occurred at the ends of 19th and 20th century Mw ≥ 6.5 fault ruptures, and the focal mechanisms were the same as the earlier main shock. Their results suggest that modern M ≥ 4.0 earthquakes may be used to define where past strong earthquake ruptures occurred and the focal mechanisms of those earthquakes, even if there is no or limited historical record of the main shocks. To test the applicability of Ebel and Chambers’ (2016) theory, we conducted a statistical test for ten significant historical earthquakes in western China. We analyzed the number of M ≥ 3.0 earthquakes from 2003 to 2018 that are near the ends of the ruptures versus those near the centers of the ruptures. The results show seven earthquakes follow Ebel and Chambers’ (2016) hypothesis whereby M ≥ 4.0 earthquakes occur at the ends of past major ruptures. The phenomenon of moderate to large earthquakes occurring at the ends of earlier large ruptures becomes more pronounced as the smallest magnitude in the data set is reduced from M 4.0 to M 3.0. For the remaining three earthquakes, two show a relatively lack of seismicity, both at the ends and in the middle of the rupture, whereas one shows that M ≥ 4.0 earthquakes in the middle of the rupture. Our results indicate that the theory of Ebel and Chambers (2016) is potentially an effective method to identify the location of past major ruptures in western China. In future work we will consider additional cases.

Citation
Zhang, Y., & Mooney, W. D. (2019, 08). Evaluating Seismicity Patterns in Western China. Poster Presentation at 2019 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)