美国斯坦福大学Segall, Pau小组在研究破火山口塌陷地震中应力驱动的复发和前兆矩率激增中取得进展。相关论文于2024年2月5日发表在《自然—地球科学》杂志上。

研究小组分析了2018年Kilauea火山(美国夏威夷)高度特征的火山口崩塌地震的地震活动性和变形数据，其平均复发间隔为1.4天。这些事件为应力诱发地震复发提供了独特的测试，并记录了五级以上主震之前的过程。该研究表明，从近场变形测量推断应力历史，可以很好地预测复发间隔，并且周期平均地震活动性揭示了在主震前几分钟的一个关键阶段，在该阶段地震变得越来越大，地震矩率急剧上升。

最后15分钟的平均力矩率(平均周期持续时间的0.7%)是背景的4.75倍，这是一个非常显著的变化。该研究团队推断，随着平均应力的增加，断裂更有可能克服几何障碍并变得更大，从而导致特征性的全断层断裂。这些发现意味着应力非均质性影响地震成核和增长，包括潜在的危险的构造断层。

据悉，预测地震的复发时间和了解地震发生之前的物理过程是地震学中两个突出的问题。虽然大地测量记录了弹性应变积累，但大多数断层的复发间隔比可用的测量长。前震提供了主震前过程的主要观察结果，但序列之间的可变性限制了对破坏前行为的概括。

附：英文原文

Title: Stress-driven recurrence and precursory moment-rate surge in caldera collapse earthquakes

Author: Segall, Paul, Matthews, Mark V., Shelly, David R., Wang, Taiyi A., Anderson, Kyle R.

Issue&Volume: 2024-02-05

Abstract: Predicting the recurrence times of earthquakes and understanding the physical processes that immediately precede them are two outstanding problems in seismology. Although geodetic measurements record elastic strain accumulation, most faults have recurrence intervals longer than available measurements. Foreshocks provide the principal observations of processes before mainshocks, but variability between sequences limits generalizations of pre-failure behaviour. Here we analyse seismicity and deformation data for highly characteristic caldera collapse earthquakes from 2018 Kīlauea Volcano (Hawaii, USA), with a mean recurrence interval of 1.4days. These events provide a unique test of stress-induced earthquake recurrence and document processes preceding mainshocks with magnitude greater than five. We show that recurrence intervals are well predicted by stress histories inferred from near-field deformation measurements and that cycle-averaged seismicity reveals a critical phase, minutes before mainshocks, where earthquakes grew larger and seismic moment rate surged dramatically. The average moment rate in the final 15minutes (0.7% of the mean cycle duration) was 4.75 times the background, a highly significant change. We infer that as the average stress increased, ruptures were more likely to overcome geometric barriers and grow larger, leading to characteristic, whole-fault ruptures. These findings imply that stress heterogeneity influences both earthquake nucleation and growth, including on potentially hazardous tectonic faults.

DOI: 10.1038/s41561-023-01372-3

Source: https://www.nature.com/articles/s41561-023-01372-3