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Global frequency of oceanic and continental supershear earthquakes
Nature Geoscience ( IF 15.7 ) Pub Date : 2022-10-31 , DOI: 10.1038/s41561-022-01055-5
Han Bao , Liuwei Xu , Lingsen Meng , Jean-Paul Ampuero , Lei Gao , Haijiang Zhang

Earthquakes are supershear when their rupture speed is faster than that of the seismic shear waves produced. These events are rare, but they can be highly destructive owing to the associated strong ground shaking, and understanding why they occur may provide insights into fault mechanics. Only a few supershear earthquakes have been reported previously, most of which were continental. Here we perform a systematic global search for supershear earthquakes by analysing seismic data from all large (Mw ≥ 6.7) shallow strike-slip earthquakes occurring between 2000 and 2020. Based on the rupture speeds determined by slowness-enhanced back-projection, and the identification of Rayleigh Mach waves, we identify four oceanic earthquakes consistent with supershear events. We find that at least 14.0% of large earthquakes during the study period were supershear, with oceanic events occurring as frequently as continental ones. We further observe a wider range of stable rupture speeds during supershear events than predicted by two-dimensional fracture mechanics theory, which we attribute to the presence of fault damage zones or slip obliqueness. The transition to and propagation of supershear earthquakes may be promoted in oceanic settings due to the thicker crustal seismogenic zones and the material contrast at oceanic–continental boundaries.



中文翻译:

海洋和大陆超剪切地震的全球频率

当地震的破裂速度快于产生的地震剪切波的速度时,地震是超剪切的。这些事件很少见,但由于相关的强烈地面震动,它们可能具有高度破坏性,了解它们发生的原因可能会提供对断层机制的见解。以前只报道过几次超剪切地震,其中大部分是大陆性地震。在这里,我们通过分析来自所有大型 ( M w ≥ 6.7) 发生在 2000 年至 2020 年之间的浅层走滑地震。根据慢度增强反投影确定的破裂速度和瑞利马赫波的识别,我们确定了与超剪切事件一致的四次海洋地震。我们发现,研究期间至少 14.0% 的大地震是超切变,海洋事件的发生频率与大陆事件一样频繁。我们进一步观察到超剪切事件期间的稳定破裂速度范围比二维断裂力学理论预测的范围更广,我们将其归因于断层损伤区或滑动倾斜的存在。由于较厚的地壳发震区和大洋-大陆边界的物质对比,在海洋环境中可能会促进向超剪切地震的过渡和传播。

更新日期:2022-11-01
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