Click on the links below to view animations created specifically for Earth: Portrait of a Planet.
Animations require Macromedia's Flash Plug-in.

Types of Faults

This animation shows the differences between the three types of faults and illustrates how they are formed. View 1 shows a normal fault, View 2 shows a reverse fault, and View 3 shows a strike-slip fault.

Offset Fence Along San Andreas Fault

The photo shows a wooden fence built across the San Andreas Fault. During the 1906 San Francisco earthquake, slip on the fault broke and offset the fence; the displacement of the fence indicates that the fault is strike-slip, as we see no evidence of up or down motion. The amount the fence was offset indicates the displacement on the fault.

Seismic Wave Motion

Seismologists distinguish between different types of seismic waves based on how they move, and whether they travel along the Earth’s surface (surface waves) or pass through its interior (body waves). This animation shows two types of body wave motion: View 1 shows shear body waves (also called S-waves) and View 2 shows compressional body waves (P-waves).

How a Seismograph Works

Seismologists use two basic configurations of seismographs, one for measuring horizontal ground motion, like the one shown in this animation, and the other for measuring vertical ground motion. Both work on the principle of inertia as described by Newton’s law, which states that an object at rest tends to remain at rest unless acted on by an outside force. Thus, during an earthquake, vibrations cause the frame of the seismograph to move. The pendulum apparatus remains fixed as the paper cylinder moves back and forth beneath it.

Additional Resources

The abundance of geology-related websites speaks to the active and exciting nature of this field. In the space below we link to external websites that explore topics covered in this chapter.

These links are selected carefully and updated regularly; however, their contents may change over time. Please click here to report a bad or missing link.

» Search for specific topics » Browse the Link Library

	Earthquake Hazards Program 9/20/2004 USGS
		Information on worldwide earthquake activity, earthquake science, and earthquake hazard reduction.

	Animated Graphics: Faulting 9/20/2004 PBS
		Scroll down to see animated gifs that illustrate normal, blind thrust, strike slip and dip slip faulting.

	Savage Earth: Earthquake! 9/20/2004 PBS
		This animation illustrates the movement of an earthquake as it travels outwards from its focus.

	Savage Earth: Tsunami Attack 9/20/2004 PBS
		This animation shows how a tsunami may form as the result of fault slip displacement of the sea-floor surface.

	What is Soil Liquefaction? 10/14/2004 University of Washington
		This page explains when, where, why, and how shocks and vibrations can cause soil to become liquid and includes informative photos, animations and laboratory simulations.