Images

The standard deviation is how much a set of data is different from the curve it should make when plotted on a graph. Or, the square root of the average of the squares of deviations about the mean of a set of data. Standard deviation is a statistical measure of spread or variability.

When the force trying to make the block (m) slip becomes greater than the frictional force causing it to stick, the block will slip.

The dots on the left make a regular pattern, but the dots on the right make a random, or stochastic, pattern.

Strain is the small changes in length and volume associated with deformation of the earth by tectonic stresses or by the passage of seismic waves.

Teleseismic is pertaining to earthquakes at distances greater than 1,000 km from the measurement site.

A transform fault is a special variety of strike-slip fault that accommodates relative horizontal slip between other tectonic elements, such as oceanic crustal plates. Often extend from oceanic ridges.

A velocity structure is a generalized regional model of the earth's crust that represents crustal structure using layers having different assumed seismic velocities.

A sketch of the thinner crust and thicker mantle. The crust and top portion of the mantle are labelled "Lithosphere "strong'" and the bottom portion of the mantle (bottom) labelled "Asthenosphere "weak.'" 

A diagram with 3 yellow squares with arrows pointing to indicate steps. The first step is labelled "Time 1: pure parent isotope," the second step is labelled "After 1 half life: 1/2 parent and 1/2 daughter isotope," and the third step is labelled "After 2 half lives: 1/4 parent and 3/4 daughter isotopes." 

A diagram showing the Earth's crust with continental and oceanic crust.

The crust is the outermost major layer of the earth, ranging from about 10 to 65 km in thickness worldwide. The uppermost 15-35 km of crust is brittle enough to produce earthquakes.

Fault scarp produced by the M7.1 Hector Mine, Calfornia earthquake. (Photo by Ken Hudnut, U.S. Geological Survey)

Focal mechanism examples. A fault plane solution is a way of showing the fault and the direction of slip on it from an earthquake, using circles with two intersecting curves that look like beach balls. Also called a focal-mechanism solution.

Illustration of Isaac Newton sitting under an apple tree, a reference to the well-known story of the epiphany Newton had when an apple fell on his head and lead to him discovering gravity.

Photo of the Grand Canyon located in Grand Canyon National Park, Arizona, Untied States.

Photo of GPS site with instrument on a tripod and a solar panel. (Photo by John Galetzka, U.S. Geological Survey)

Diagram of great circle. The shortest path between two points on the surface of a sphere lies along a great circle.

Liquefaction and lateral spreading occurred along the west side of Sunset Lake trailer park in Tumwater.

Lithologic cross-section example with descriptions of lithology at different depths. 

Compare the fault area of the magnitude 7.3 (top) with that of the magnitude 5.6 (smallest one near the bottom).

Liquefaction potential map of the San Francisco Bay Area, California. (Image courtesy of the Association of Bay Area Governments-ABAG)

Plate Tectonics is the theory supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. Slip on faults that define the plate boundaries commonly results in earthquakes.