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Earthquake Geology & Paleoseismology

USGS and university geologists study the walls of a trench across a recently discovered strand of the Seattle fault.

Earthquake geology in the broad sense is the study of the history, effects, and mechanics of earthquakes within and on the Earth's crust. Most often, earthquake geology is synonymous with active tectonics, a term used to describe the study of tectonic movements that are expected to occur within a future time span of concern to society. Such definitions overlap considerably with other research topics on this site, such as Crustal Deformation, Seismology and Earth Structure, and Strong Motion and Site Response. Important aspects of earthquake geology include the study of tectonic landforms on the Earth's surface and folds and faults within its crust produced by many earthquakes over thousands to millions of years.

Paleoseismology is the study of the timing, location, and size of prehistoric earthquakes. Paleoseismology differs from other aspects of earthquake geology in its focuses on the almost instantaneous deformation of landforms and sediments during individual earthquakes. This focus permits study of the distribution of earthquakes in space and over time periods of hundreds to tens of thousands of years. Such paleoseismic histories help us understand other aspects of earthquake geology, such as regional patterns of tectonic deformation and the long-term behavior of specific faults. More importantly, knowledge of when, where, and how often, large earthquakes occur is crucial for characterizing the seismic hazard of a region.

Geologic Studies Outside of the United States

  • Multiple large earthquakes in the past 1500 years on a fault in metropolitan Manila, The Philippines
    Recent assessment of the earthquake hazard posed by crustal faults in cities highlight the need for evaluating potentially active crustal faults in urban areas. Manila--with a metropolitan population of about 10 million--is similarly subject to earthquakes on nearby crustal faults, as well as earthquakes on more distant plate-boundary faults. from BSSA publication
  • Paleoseismic Study of the Gurvan Bulag Thrust Fault: Gobi Altay, Mongolia
    Scientists studied a total of five exposures (hand-dug trenches and cleaned stream cuts) along the main Gurvan Bulag thrust, and one exposure across a subsidiary fault.
  • USGS Scientific Expedition: Earthquake in Turkey - 1999
    Scientists and engineers from the U.S. Geological Survey departed for the epicentral region on August 19, 1999, less than 2 days after the quake occurred, to join in an international scientific effort that will deploy seismic and geodetic instruments, make geologic field measurements and assess and record the structural damage.
  • USGS Scientific Expedition: Mongolia - 1998
    In September 1998, USGS and other scientists investigated surface ruptures associated with the 1905 Bulnay earthquakes. During the field expedition, they sent updates of their observations and progress in near real-time. These reports summarize their geologic findings and approaches, along with their experiences and observations from Mongolia (along with a few photographs, too).

Quaternary Faults & Folds

Regional Studies

California

  • Portfolio of Landscape, Seascape and Faults of the San Francisco Bay Area
    Developed by Robert E. Crippen (JPL) and Ross Stein (USGS), these images drape Landsat TM satellite imagery over Digital Elevation Models to show the bay as it has never been seen before.
  • Quaternary-Active Fault Map
    Shows the distribution of faults in the San Francisco Bay region most likely to generate future earthquakes, with information about active faults and how geologists find them and study them.
  • San Francisco Bay Region Geologic Map
    Shows the distribution of geologic materials and geologic structures that are visible at the Earth's surface, with information about geologic materials, geologic time, fossils, and the geologic history of the San Francisco Bay region.
  • The Hayward Fault
    An introduction to and photographic tour of the Hayward fault, by Dr. Sue Hirschfield, California State University, Hayward.
  • The Parkfield, California Earthquake Experiment
    A comprehensive, long-term earthquake research project on the San Andreas fault to better understand the physics of earthquakes.
  • The San Andreas Fault
    Good general introduction to the fault, its geologic setting and the earthquakes on it, with nice photos. By Sandra S. Schulz and Robert E. Wallace.

Intermountain West

  • Intermountain West Project
    Collecting and analyzing data that directly contribute to improving the National Seismic Hazard maps, and that better quantify the frequency and characteristics of earthquake-generated strong ground motion in seismically hazardous parts of the Intermountain West, particularly in the more heavily populated urban corridors of the region.

Pacific Northwest