Borehole Geophysics and Rock Mechanics

The initiation and propagation of earthquake ruptures depend upon the mechanical behavior of fault rocks and fluids at depths of several kilometers or more. Using borehole geophysical measurements in conjunction with laboratory studies, USGS scientists determine the temperature, stress, and fluid-pressure conditions at the depths where earthquakes occur and characterize the mechanical behavior of fault-zone materials at realistic in-situ conditions. This knowledge is combined with surface-based geophysical observations, measurements of tectonic strain accumulation, and other information to yield improved models of the earthquake cycle.

• Heat Flow Studies

  The Earth's internal heat drives many geologic processes and, where it is locally concentrated, this heat can be manifested as volcanoes, hot springs, and other thermal features. The USGS Heat Flow Studies Group conducts research on the thermal regime of the Earth’s crust.

• Rock Physics Laboratories

  Scientists study rock properties in laboratory settings that simulate conditions deep in the earth where earthquakes occur to improve our knowledge of seismogenic faulting.

• The San Andreas Fault Observatory at Depth

  Scientists drilled a 4km-deep hole into the San Andreas fault zone near Parkfield to learn more about the nature of stresses responsible for earthquakes. The study addresses fundamental questions regarding the physical and chemical processes acting within the San Andreas and other major plate-bounding faults.