Aftershock Sequence of the Izu Earthquake of August, 1956

An Example of Aftershock Observation by a Single Stationby S. Suyehiro

Abstract

Many aftershocks of the earthquake off Izu Peninsula were observed at the Matsushiro Seismological Observatory by two kinds of seismometers, the standard torsion seismometers and the short period vertical electromagnetic seismometer. Since no other seismological stations equipped with sensitive seismometers were available, the aftershocks have been investigated by the data obtained at Matsushiro alone.
First, the aftershocks are selected on the qualitative b a sis, and then in order to determine the magnitude of each shock a method to determine the magnitude by seismometer other than the standard seismometer is proposed on the theoretical and observational basis.
Lastly, some characteristics of the aftershock sequence are presented.