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

8 W. H. h‘. Lee, H. Meyers, and K. Shimazaki5. Major Historical EarthquakesThe traditional definition of a major earthquake is that its magnitude be greaterthan or equal to 7. However, it was pointed out that this magnitude criterionprecluded important earthquakes of smaller magnitude. WDC-A has resolved thisproblem by considering two sets of major historical events: (a) those of magnitudegreater than or equal to 7 and (b) events located in and around the United Statesof smaller magnitude, but important for other criteria (see WDC-A Report SE22). This policy could be adopted for selection of events whose records are to becopied in other countries. A useful guide in identifying significant earthquakes hasbeen published by WDC-A: “Catalogue of Significant Earthquakes 2000 BC-1979:Including Quantitative Casualties and Damage” (Report SE-27, July 1981).6. Available Seismological RecordsThe President of the European Seismological Commission (ESC), Dr. Ritsema,reported recent activities related to this project. He mentioned that, upon requestby WDC-A, ESC has identified seismological stations where historical seismogramsare stored in Europe. For this purpose the Commission had sent questionnaires toselected members for their suggestions of five to ten stations in western Europe thatwould be willing to participate in the U.S.-organized project. Some stations posedfinancial conditions in participation, but if these difficulties could be solved theywould hope to join the project actively. He had received positive replies from severalobservatories to participate. They are stations at Toledo (records available since1909), Stuttgart (1910), Gottingen (1903), Uppsala (1904) , Vienna (1906), Uccle(1906), De Bilt (1908). In addition, Dr. Lopez Arroyo stated that the followingstations in Spain may offer access to records for WDC-USGS project. They possessrecords from the early 19OO’s, for instance, San Fernando station has data from 1899,Cartuja from 1903, Toledo from 1909, etc. He warned that these old seismograms arefragile, not stored in good condition, and urged copying quickly before destruction.Dr. Nikolaev expressed the possible participation from observatories in the easternEuropean countries. They are: Alma Ata which has records from 1922, Bakufrom 1940, Vladivostok from 1929, Irukutsk from 1901, Tbilisi from 1940, etc. Inaddition, several stations from the regions such as German Democratic Republic andBulgaria, are now in a position to join in the activities. He stressed that copyingwork may be carried out by local scientists if appropriate sets of copying equipmentare provided. It is preferable to work with mobile equipment at individual stationsinstead of gathering records at a central point. Prof. Miyamura commented thatsome stations stored old records from other stations in the past, such as Gottingenand Leningrad. This fact should be taken into account in selecting stations whoserecords may be copied. Dr. Denham explained the situation in Australia. Somestations, such as Riverview, started observing from early in this century, and heexpects its records would be in good condition. It was, however, very unfortunatethat floods in 1970 destroyed many of the old records from the Brisbane station.The main problem in his country would probably not be the lack of funds, but toobtain technical staff to carry out the copying. However, with a reasonable leadtime, the available records could be annotated properly for copying. It was also