Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

132 A. D. Gvishiani and Wilbur A. Rinehartwas used for selecting the seismograms to be photographed for the Historical SeismogramFilming Project, begun in 1977 under the auspices of the U.S. GeologicalSurvey. In the first stage, Dr. Gordon Stewart of the California Institute of Technologyprepared a list of significant earthquakes from the time when seismometerswere first used at observatories throughout the world (about 1900). The final list ofearthquakes for the Historical Seismogram Filming Project contained data on earthquakesthat have a magnitude sufficient to be recorded by the relatively low-gainseismometers of the 1900 to 1960 time period. Their locations are shown on a worldmap in Figure 1. Seismograms of the events included in this list were microfilmed,forming the base of the NGDC archive of historical seismograms.In the seismological data base maintained by NGDC, a unified format is used.The major data fields are: (1) source code; (2) year-month-day; (3) hour-minutesecond;(4) latitude; (5) longitude; (6) depth; (7) rng magnitude; (8) intensityI,; (9) Ms magnitude; (10) geological effects codes; (11) cultural effects, codes;(12) Flinn-Engdahl codes; (13) magnitude reported by other sources; (14) InternationalDeclared Event (IDE); (15) number of stations and quality indicator;(16) source authority for time and coordinates; and (17) local magnitude - typeand source code. This format makes the earthquake data available using FOR-TRAN 77 retrieval programs.Another large earthquake computer-readable data base wits independently developedbeginning in 1975 by the Institute of the Physics of the Earth (IPE), Academyof Sciences, USSR. A significant part of this data base is information on historicalseismicity. Data exchange between IPE and NGDC gave an opportunity to fill inthe gaps in both data bases and to have sufficient and complete information aboutearthquakes in all regions of the world. The NOAA data base was supplementedby the earthquake hypocenter data file of the USSR. In return, the worldwide catalogof the NOAA data base is regularly provided by NGDC to update the IPEdata base.As a result of the exchange of data, NGDC prepared a map (Figure 2) of thestrong earthquakes in the territory of the USSR from ancient times to 1977.6.0 5 M < 8.0Figure 1. 1900-1960 earthquake locations proposed for the historical microfilmingproject.