Historical Seismogram Filming Project: Fourth Progress Report

摘要

World Data Center A for Solid Earth Geophysics has collected, microfilmed, and archived historical seismograms from selected seismograph stations and earthquakes worldwide. The purpose of this project is to preserve and archive historically important seismograms for both present and future researchers. Acquisition of seismograms from seismograph stations at Mt. Hamilton and Pasadena, Calif., has brought the number of records in the historical microfilm archive to about 235,000.