Borehole Geophysics and Rock Mechanics
USGS scientist Dave Lockner using a diamond core drill to prepare sandstone samples for lab testing. See Rock Physics Laboratories (below) for more information on lab studies.
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.