Importance of Historical Seismograms for Geophysical Research

Abstract

Among the most important data in geophysics are the seismograms which have produced most of the basic and quantitative information concerning the seismic source and the Earth's interior. Modern seismographic instruments provide high quality seismograms with a wide dynamic range and frequency band. The analysis of these seismograms, together with the recent developments in theory and methodology, has resulted in an order of magnitude increase, both in quantity and quality, of our knowledge of the Earth's interior and physics of earthquakes. However, the earthquake cycle is a long-term process so that study over a long period of time is essential for a thorough understanding of the earthquake phenomenon. Furthermore, since earthquakes may not repeat in exactly the same way, detailed analyses of earthquakes in the past are important. For more than a century, a large number of seismograms have been recorded at many stations in the world, but many of them have not been fully utilized mainly because theories and methods had not been developed well enough to fully interpret the seismograms at the time when the earthquakes occurred. In many cases, methods developed in later years enabled seismologists to investigate existing records of earlier events, searching for further information. In this paper, we illustrate the importance of historical seismograms for various geophysical studies.

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