Images

Diagram of dipping slab with different focal depth events. The focal depth refers to the depth of an earthquake hypocenter.

The geologic time scale showing each eon, era, period, epoch, and their associated ages.

Photo of bridge.  Geotechnical means referring to the use of scientific methods and engineering principles to acquire, interpret, and apply knowledge of earth materials for solving engineering problems.  

Horst and graben diagram. A graben is a down-dropped block of the earth's crust resulting from extension, or pulling, of the crust. 

Iceland and plate motions. Kinematic refers to the general movement patterns and directions of the earth's rocks that produce rock deformation.

Plot showing least squares fit. When plotting data points on a graph, the least-squares-fit is the line or curve that comes closest to going through all the points.

The Landers fault (red lines at left) and the Hector Mine fault and its aftershocks (red lines and circles at right). The Hector Mine earthquake was a magnitude 7.1, and it produced thousands of aftershocks.

The natural frequency is the frequency at which a particular object or system vibrates when pushed by a single force or impulse, and not influenced by other external forces or by damping. If you hold a slinky by one end and let it hang down and then give it one push up from the bottom, the rate of up-and-down motion is its natural frequency.

A P wave, or compressional wave, is a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving.

Diagram of period.  The period is the time interval required for one full cycle of a wave.

Moment = ? A D

? = shear modulus = 32 GPa in crust, 75 GPa in mantle

A = LW = area

D = average displacement during rupture

The New Madrid seismic zone in Central U.S.

A seismic zone is an area of seismicity probably sharing a common cause. 

A seismogram is a record written by a seismograph in response to ground motions produced by an earthquake, explosion, or other ground-motion sources.

A slab is the oceanic crustal plate that underthrusts the continental plate in a subduction zone and is consumed by the earth's mantle.

This turn-of-the-century wooden residence in Los Gatos sustained major damage when it moved off its foundation during the October 17, 1989, M7.1 Loma Prieta, California earthquake.

A surface wave is a seismic seismic wave that is trapped near the surface of the earth.

A tsunami is a sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine slides, or exploding volcanic islands.

This image of the Los Angeles region combines this information to predict the total amplification expected in future earthquakes from local geologic conditions or site effects.

A diagram showing a slice of the Earth's lithosphere, including continental crust, oceanic crust, asthenosphere, and the upper mantle.

An illustration showing two stick figures doing basement excavations, one with a frown that excavated into the labelled hard, stable bedrock on the left and the other with a smile that excavated above the labelled bedrock surface.  

A diagram of a blind thrust fault resulting in ductile rock layers folding over the fault and leaving the fault under the surface.