This reference provides an introduction to the geoid, the equipotential surface of the Earth's gravity field which best fits global mean sea level. There is a narrative of early attempts to describe the geoid, and schematic diagrams showing the geoid and its relationship to Earth's crust, local mean sea level, orthometric heights, and local dynamic ocean topography. Full description.

This animation shows how P-waves (primary, or compressional, waves) travel through a Slinky toy. It is accompanied by a brief written explanation that describes some of the properties of P-waves and how they are generated in a real Slinky. Full description.

In this activity, learners will look at some of the characteristic properties of aftershock sequences, and relate them to variables in two equations: the modified version of Omori's Law, and the Gutenberg-Richter relation for aftershock sequences. The database provided in this link can be searched to extract the magnitude and time-after-mainshock for selected earthquakes. From this information, users ... Full description.

These animations show how various types of waves are propagated during an earthquake. Users can see how P-waves travel at the surface, how they are reflected and refracted as they travel further from their source, and how multiple reflections can combine to create a surface wave. There is also an animation showing how S-waves were amplified by reflections from the Moho during the 1989 Loma Prieta ... Full description.

In this activity, students learn about the different types of seismic waves in an environment they can control. Using an interactive, online wave generator, they will study P waves, S waves, Love waves, and Rayleigh waves, and examine a combination of P and S waves that crudely simulates the wave motion experienced during an earthquake. A tutorial is provided to show how the wave generator is used. ... Full description.

This portal offers access to data on recent earthquakes and volcanic activity in the Pacific Northwest, particularly Washington and Oregon. Materials presented here include catalogs and data from previous earthquakes, including historic events, information on earthquake hazards and research activities of the PNSN, and links to news articles, frequently asked questions, and educational materials. Full description.

This is the homepage of the Broadband Seismic Data Collection Center (BSDCC). It features seismic data from several regional seismic networks, small aperture arrays and portable instrumental deployments. The webpage contains detailed information and research results for all the networks the Broadband Seismic Data Collection Center operates. Users can follow numerous seismic information links including ... Full description.

The Geomagnetic and Solar Activity Forecast Service is a service of the British Geological Survey. It provides data for daily local, global and solar geomagenetic activity. Data includes information projected up to 27 days ahead using a linear prediction method, up to 3 days ahead using a non-linear prediction method and smoothed monthly solar and geomagnetic activity for the next solar cycle using ... Full description.

This site features earthquake related Flash animations and real video footage. The visualizations illustrate how seismographs work, p and s waves, earthquake foci versus epicenters, tsunami formation, as well as an earthquake video recorded by security cameras. These resources portray a variety of environments and are suitable for use in lectures, labs, or other teaching activities. Full description.

A depiction of some of the Earths (blue) and the Suns (white) magnetic field lines from a global magnetospheric simulation. The green hemisphere is the inner boundary of the simulation. Full description.