This report describes how the work of K. Wadati, Charles F. Richter, Harry O. Wood, and Beno Gutenberg resulted in a way of rating earthquakes in southern California according to an instrumental analysis of the amount of energy they released in the form of seismic waves. This work resulted in the first use of the term "magnitude" for describing the amount of energy released by an earthquake, and in ... Full description.

This report describes how measurements of earthquake magnitude, as quantified by the Richter Scale, have gradually replaced measurements of intensity, as characterized by the Modified Mercalli scale. Topics include the advantages of the Richter Scale, such as open-endedness, its purely instrumental measure which doesn't require observers' reports, and its usefulness for measuring earthquakes located ... Full description.

Recordings on this site present 164 aftershocks as they were heard at one seismic recording station. They occurred after an earthquake with a magnitude of 6.2 beneath and near New Zealand. All events are heard in rapid sequence, without the true time intervals between them. The main shock was at a depth of 30 kilometers, 10 kilometers below the interface between the subducting Pacific Plate and the ... Full description.

Data collected by a new seismic observatory at the Amundsen-Scott South Pole Station indicate that it is the quietest listening post on the planet for observing shudders produced by earthquakes around the world as they vibrate through the Earth. The South Pole Remote Earth Science Observatory (SPRESO) is located eight kilometers (five miles) from the South Pole and the new seismometers were installed ... Full description.

In this activity, students use simple calculations of the travel times of seismic waves in a constant velocity spherical Earth and compare these with observations for the real Earth. They find that the Earth's interior is not homogeneous. The exercise provides suggestions about the actual nature of the Earth's interior structure. This activity will provide experience with graphing, calculations and ... Full description.

In this activity, students examine a seismogram display called a seismic record section in which each trace is a seismogram recorded at a specific seismograph station. The seismograms are plotted according to the distance (in degrees, geocentric angle) from the earthquake location and time from the earthquake origin. The traces are of the vertical component of ground motion, and have been filtered ... Full description.

In this activity, students construct a model that will allow them to experiment with thermal convection, illustrating how thermal energy can generate a flowing motion in a fluid. The thermal convection in this model is similar to the convection that is inferred for the Earth's mantle and can produce horizontal flow that can cause or is related to plate motions. Students will investigate the viscosity ... Full description.

Users can access the array of seismometers operated by the the University of California at Berkeley's Seismological Laboratory in northern and central California. The Berkeley Digital Seismic Network is an array of high-dynamic range, broadband seismometers. Data from these instruments are transmitted continuously to UC Berkeley for processing and analysis. Using the interface, visitors may create ... Full description.

This radio broadcast explains how the North Pole is constantly moving due to the rotation of the Earth, which in turn is determined by any changes in the mass distribution of the Earth. The clip is 2 minutes in length. Full description.

In this activity students plot the latitude and longitude involved in the movement of the Magnetic North Pole over a period of time, predict its location by the year 2000, and justify their reasoning. Students will discover that the Magnetic North Pole has been charted over the past several hundred years and that the pole shifts an average of 15 kilometers/year. They will also learn tha navigation ... Full description.