Berkeley Seismological Laboratory, University of California, Berkeley, CA 94720, USA.
Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.
Science. 2017 Jun 16;356(6343):1161-1164. doi: 10.1126/science.aak9547.
Establishing what controls the timing of earthquakes is fundamental to understanding the nature of the earthquake cycle and critical to determining time-dependent earthquake hazard. Seasonal loading provides a natural laboratory to explore the crustal response to a quantifiable transient force. In California, water storage deforms the crust as snow and water accumulates during the wet winter months. We used 9 years of global positioning system (GPS) vertical deformation time series to constrain models of monthly hydrospheric loading and the resulting stress changes on fault planes of small earthquakes. The seasonal loading analysis reveals earthquakes occurring more frequently during stress conditions that favor earthquake rupture. We infer that California seismicity rates are modestly modulated by natural hydrological loading cycles.
确定控制地震时间的因素对于理解地震周期的本质至关重要，对于确定与时间相关的地震危险也至关重要。季节性加载为探索地壳对可量化瞬态力的响应提供了一个自然实验室。在加利福尼亚，随着冬季潮湿月份积雪和水量的增加，蓄水会使地壳变形。我们使用了 9 年的全球定位系统（GPS）垂直变形时间序列来约束月度水文负荷模型以及小地震断层面上由此产生的应力变化。季节性加载分析表明，在有利于地震破裂的应力条件下，地震发生的频率更高。我们推断，加利福尼亚的地震活动率受到自然水文循环的适度调节。
