Dual-Initiation Ruptures in the 2024 Noto Earthquake Encircling a Fault Asperity at a Swarm Edge

Liuwei Xu, Chen Ji, Lingsen Meng, Jean-Paul Ampuero, Zhang Yunjun, Saeed Y. Mohanna, & Yosuke Aoki

Submitted September 8, 2024, SCEC Contribution #13532, 2024 SCEC Annual Meeting Poster #009

To reveal the connections between the 2024 Mw7.5 Noto earthquake and the seismicity swarms that preceded it, we investigate its rupture process through near-source waveform analysis and source imaging techniques, combining seismic and geodetic datasets. We find remarkable complexity in the initial rupture stages. A strong fault asperity, which remained unbroken in preceding seismic swarms, slows down the rupture. Then a second rupture initiates at the opposite edge of the asperity and the asperity succumbs to double-pincer rupture fronts. The failure of this high stress drop asperity drives the earthquake into a large-scale event. Within 3 km of the mainshock epicenter, 119 earthquakes of magnitude M≥3 occurred since 2021. In contrast, there was no earthquake of magnitude M≥3 from 2000 to 2020. Our observations indicate that the preceding seismic swarm or its underlying driving process likely led to the nucleation of the 2024 Noto mainshock, and the strong asperity acts as both a barrier and an asperity during this earthquake. The asperity failure is the reason why the 2024 Noto earthquake could develop into an Mw 7.5 large-scale rupture. Our study helps unravel the crucial role of fault asperities in controlling swarm migration and rupture propagation, and underscore the need for detailed seismological and interdisciplinary studies to assess seismic risk in swarm-prone regions.

Key Words
Noto earthquake, earthquake sources

Citation
Xu, L., Ji, C., Meng, L., Ampuero, J., Yunjun, Z., Mohanna, S. Y., & Aoki, Y. (2024, 09). Dual-Initiation Ruptures in the 2024 Noto Earthquake Encircling a Fault Asperity at a Swarm Edge. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology