Tag Archives: seismicity

A Different Kind of Short Story

Hey all, not sure if anyone still looks on this site after such a long period of inactivity (My bad). I’ve been pretty busy with finishing up my degree but I never really stopped writing. It just shifted focus. I just wanted to post a sample of the type of stuff I’ve been doing.

Below I have a science highlight for one of my recent papers (it ended up being 20+ pages so I didn’t want to post the actual thing here). Water and geology are my passions, along with writing. So I thought it’d be cool to mix my worlds together a little bit. And who knows, maybe you’ll learn something too 🙂

Study Finds That California Summers Contribute to Seismic Events

Jacob Edwards 5/7/18


With the changing of the seasons in California, there are many factors that affect the likelihood of earthquakes. The most prevalent of these seasonal controls is called hydrologic loading. During the wet California winter, the weight of water and snow compresses the continental crust. When that water and snow is evaporated in the summer, the crust raises again. This happens around the late-summer or fall, depending on the area of California. The type of ground that the water is absorbed into plays a part as well. It can affect how long it takes the water weight to drain or evaporate. Areas like the central valley have more soil to hold and retain the winter rains, whereas the coastal and Sierra Nevada mountain ranges have less of a soil layer and also drain down into the valley.  (Nature, http://doi.org/10.1038/nature13275, 2014)

The up and down movement of the crust, especially in the coastal mountain ranges helps to loosen the San Andreas fault system. When the weight of the loaded water is removed in the late summer, the strike-slip faults of the San Andreas unclamp, making it easier for them to slip and cause an earthquake. (Nature, http://doi.org/10.1038/nature13275, 2014)

The Uniform California Earthquake Rupture Forecast model geometry or UCERF3 is a tool used by Johnson et. al in the scientific paper: Seasonal water storage, stress modulation, and California seismicity, 2017. It was a collective effort by the geology community to measure the likelihood of fault failure of nearly every fault in California. Johnson et. al used the data to see just how much stress these faults undergo every year and when it was at its maximum. These times happened to be when the crust was under its maximum stress due to hydrologic loading. Then Johnson et. al compared this data to the historical records of earthquakes in California. The majority of earthquakes in the past fit this model, happening when stress from the weight of winter rain and snow was at its greatest. (Science Vol. 356 Issue 6343 http://doi.org/10.1126/science.aak9547, 2017)


  1. Johnson, Christopher W., et al. “Seasonal Water Storage, Stress Modulation, and California Seismicity.” Science, vol. 356, no. 6343, 2017, pp. 1161–1164., doi:10.1126/science.aak9547.
  2. Amos, Colin B., et al. “Uplift and Seismicity Driven by Groundwater Depletion in Central California.” Nature, vol. 509, no. 7501, 2014, pp. 483–486., doi:10.1038/nature13275.