Earthquake Hazards

Earthquake Processes and Effects

The overarching theme of this research is for scientists to discover as much as they can about earthquakes and faulting from field and laboratory observations, and to combine this with geophysical, geological, geochemical, and mathematical (including computational) modeling of earthquake sources and fault zones so as to best improve USGS earthquake hazard assessments.

Overview  |  Tracking Stress Buildup and Crustal Deformation  |  Fault Slip Rates and Post-Earthquake Motions

Ground Movement and Ground Shaking  |  Cone Penetration Testing (CPT)  |  Rock Physics Lab

San Francisco Bay Area Arrays and East Bay Seismic Experiment  |  Neogene Deformation

 

Overview

San Andreas Fault and its various environments in the Southern California area

The San Andreas Fault and its various environments in the Southern California area, including both mountain building and valley subsidence close together. (Public domain.)

The high level of earthquake activity and the complexity of the fault systems throughout California area provides a unique natural laboratory for the study of the physics of earthquakes. Scientists are studying fault interaction by comparing the seismic behavior in California to analogous areas in the world with large strike-slip faults, to provide insight into possible past and future earthquakes in the region.

In addition, earthquakes are generated in the laboratory under controlled conditions to learn how they start and what indications there might be that they are about to happen. Also, fault zone materials are carefully tested to learn about the physical and chemical processes that control earthquakes.

The project works in close collaboration with regionally focused projects and with the National Seismic Hazard Mapping (NSHM) project in order to support those efforts at issuing earthquake hazard products. This research strives to increase the quality and impact of these products, and to reduce their uncertainties, through multidisciplinary research aimed at better understanding the earthquake process.

Some of the key scientific questions scientists seek to answer:

  • How is stress loaded onto faults as a function of space and time by both plate motions and other geological processes?
  • How do the stresses redistributed by one earthquake affect the probability of future events?
  • Do identifiable earthquakes recur with some average repeat time and definable variation or is each earthquake unique? How does the structure of faults control the nucleation of small earthquakes and their growth into larger ones and what does this predict about the distribution of sizes of earthquakes we can expect in a region or along a fault?