Slow rupture in a fluid-rich fault zone initiated the 2024 <i>M</i><sub>w</sub> 7.5 Noto earthquake.

Ma, Zhangfeng; Zeng, Hongyu; Luo, Haipeng; Liu, Zemin; Jiang, Yu; Aoki, Yosuke; Wang, Weitao; Itoh, Yuji et al. · Science · 2024

basic_science · Level V

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Abstract

The 2024 moment magnitude 7.5 Noto Peninsula (Japan) earthquake caused devastation to communities and was generated by a complex rupture process. Using space geodetic and seismic observations, we have shown that the event deformed the peninsula with a peak uplift reaching 5 meters at the west coast. Shallow slip exceeded 10 meters on an offshore fault. Peak stress drop was greater than 10 megapascals. This devastating event began with a slow rupture propagation lasting 15 to 20 seconds near its hypocenter, where seismic swarms had surged since 2020 because of lower-crust fluid supply. The slow start was accompanied by intense high-frequency seismic radiation. These observations suggest a distinct coseismic slip mode reflecting high heterogeneity in fault properties within a fluid-rich fault zone.