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Presents information on the Aniakchak volcano in Alaska. Functions of seismographs; Characteristics of Alaskan volcanoes; Features of the Aniakchak volcano; Information on the eruption of the Aniakchak volcano.

Provides details of how an earthquake that originated in Tokyo, Japan was recorded in Washington D.C. in 1923. Use of seismographs in the prediction of earthquakes; Method used for locating the center of the earthquake; Factor responsible for the earthquake; Role of seismic frequency in determining the magnitude of the earthquake; Observations of seismic activity in the Tokyo Bay.

Provides a historic account of the great earthquake at San Francisco, California as written by the seismograph of the U.S. Weather Bureau. Measurement of the earth vibration; Amplitude and period of the waves; Speed of propagation.