Faults, Earthquake Geology, and Special Earthquake Studies

The goals of USGS earthquake geology and paleoseismology research are 1) to make primary observations and develop ideas to improve our understanding of the geologic expression of active faulting, and 2) to acquire data that will improve the National Seismic Hazard Model. Geological research allows us to characterize faults, including the identification of secondary seismogenic structures, to study...

The Intermountain West contains some of the fastest growing urban centers in the United States, and several are exposed to a substantial level of seismic hazard. It is critical to accurately quantify this hazard, and ultimately, the associated risk.

The Central and Eastern U.S. (CEUS) is subject primarily to moderate earthquakes like the 2011 Virginia Mw5.8 earthquake, the ongoing induced earthquakes primarily in the central U.S., the ongoing 2019-2020 earthquake sequence in southern Puerto Rico, and the 2020 M5.1 earthquake in North Carolina. These earthquakes have all caused moderate to light damage, but they highlight the potential for a...

The principal faults of the San Andreas Fault (SAF) system and Pacific-North American plate boundary in northern California pose significant hazard to people, infrastructure, and the economy. Interestingly, in the later twentieth and early twenty-first centuries, the earthquakes that have affected the United States most significantly have not ruptured the primary faults of the greater SAF system...

The USGS employs a variety of methods, including LIDAR, the Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), creepmeters, and alinement arrays to make geodetic measurements. Geodetic measurements of crustal motion are uniquely suited to observing a range of processes relevant to earthquake occurrence and effects that cannot be observed with other methods such as...

Large earthquakes on the 1100-km-long plate-boundary fault of the Cascadia subduction zone beneath Washington, Oregon, and northern California pose a significant hazard to population centers of the U.S. Pacific Northwest. Tsunamis from a Cascadia megathrust earthquake, and from earthquakes on other trans-Pacific subduction zones, pose a threat along the Pacific Coast in Washington, Oregon, and...

Southern California has the highest level of earthquake risk in the United States, with half of the expected financial losses from earthquakes in the Nation expected to occur in southern California. Sitting astride the Pacific - North American plate boundary at the Big Bend of the San Andreas Fault, Southern California has over 300 faults capable of producing magnitude 6 and larger earthquakes...

USGS scientists conduct research and provide scientific response to damaging earthquakes in active tectonic regions of the United States and around the world.

Studying Earthquake Hazards and Rifting Processes in the Imperial and Coachella Valleys

Repeated earthquakes shape the Earth over the millennia and fault zones often have unique and diagnostic landforms caused by the faulting process. In order to measure the rate at which the Earth’s crust deforms between, during and after earthquakes, precise measurements need to be made along active faults zones.

The constant plate tectonic motions between the Pacific and North American plates guarantees that the crust in the western US is continually building up stress. Crustal deformation refers to the changing earth’s surface caused by tectonic forces that are accumulated in the crust and then cause earthquakes.