Quake: Physics of Earthquakes

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Borehole Geophysics and Rock Mechanics

Earthquake Research

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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.

The San Andreas Fault Observatory at Depth
Scientists will drill a 4-km-deep hole into the San Andreas fault zone near Parkfield in order to learn more about the nature of stresses responsible for earthquakes. The study will address fundamental questions regarding the physical and chemical processes acting within the San Andreas and other major plate-bounding faults.

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

Heat Flow Studies and California Heat Flow Database
The Heat Flow Studies Group conducts research on the thermal regime of the Earth's crust, with a focus on seismic hazards, geothermal energy, hydrologic processes, and the evolution of sedimentary basins.

Modeling of fault zone hydraulics and rheology of the San Andreas Fault near Parkfield
Scientists are developing models for the time-evolution of hydraulic and rheological properties of fault zone rocks throughout the earthquake cycle. These models will be applied to the San Andreas Fault near Parkfield, where the soon-to-be-performed drilling through the fault at depth will provide a rare opportunity to test model predictions.

Parkfield Earthquake Experiment

The USGS and the State of California are conducting a multi-disciplinary, long-term project aimed at better understanding the earthquake process. The project involves recording a variety of geophysical signals before, during and after the expected earthquake at Parkfield, testing a short-term earthquake prediction, and (proposed) drilling into the San Andreas fault.

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