Faults, Earthquake Geology, and Special Earthquake Studies

Photo of scientists using balloon Lidar
USGS scientists and collaborators surveying the San Andreas Fault using a 3D laser scanner lofted by a helium balloon.

Near-Field Geodesy

The USGS is at the cutting edge of measuring ongoing deformation of the Earth’s surface, a field known as geodesy. 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. USGS scientists have long established alignment arrays, which are stable markers that cross faults zones and can be measured to determine the rate of slip on the fault zone. USGS scientists, along with collaborators from universities, have established a network of hundreds of alignment arrays across the major faults of northern California.

USGS scientists are also at the leading edge of utilizing 3D laser scanning to map the Earth’s surface and objects at and near the Earth’s surface in order to quantify the rates and patterns of crustal deformation. This includes using 3D laser scanning technology from tripod mounts as well as mobile platforms (vehicles, backpacks, balloons, etc) that enable measurement of landscapes at centimeter-level precision over large areas. These techniques allow USGS scientists to provide rapid scientific response to damaging earthquakes, and to advance our understanding of the physics of earthquakes and how earthquakes affect the Earth in three-dimensions and through time.

photo of mobile laser scanner
USGS scientist Ben Brooks operating a truck-mounted mobile laser scanner capable of measuring fine-scale details of surface deformation following an earthquake.
map depicting fault slip following the Napa earthquake
USGS scientists were able to use 3D laser scanner technology to map the patterns of fault slip that occurred in the days weeks and months following the 2014 South Napa Earthquake. This map shows the direction and amount of offset that occurred across the fault in one study area.
USGS geologists responded to the 2014 South Napa Earthquake using tripod and mobile laser scanning technology to map and measure the deformation that occurred at the Earth’s surface. Here, USGS student interns create a 3D scan of the fault surface rupture trace through a horse paddock.
USGS scientists use a variety of measurement methods such as this backpack mounted mobile 3D laser scanner to image faults zones and better understand movement along faults.