Seasonal stress modulation on active California fault structures

Christopher W. Johnson, Yuning Fu, & Roland Bürgmann

In Preparation October 1, 2016, SCEC Contribution #7290

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.

Johnson, C. W., Fu, Y., & Bürgmann, R. (2016, 10). Seasonal stress modulation on active California fault structures. Oral Presentation at State of stress in the Earth.