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

SOME REMARKS ON HISTORICAL SEISMOGRAMSAND THE MICROFILMING PROJECTS. Ma'yamuraOki Electric Industry, Ltd.Tokyo, JapanABSTRACTFor the selection of earthquakes in the seismogram filming project, differentbasic catalogs are compared. In particular, the catalogs preparedby World Data Center A (WDC-A) for the microfilming project are examined.The geographical inhomogeneity of magnitude threshold is discussed.The importance of selecting rare earthquakes far from the seismiczones is emphasized. Examples of rare earthquakes in the different partsof the Earth are shown in tables and maps.Beside magnitude, damage is usually considered for the selection ofearthquakes to be filmed. However, unlike magnitude catalogs, we have noaccurate global damage catalog of destructive earthquakes. A provisionallist of destructive earthquakes has been prepared, based on Rika Nenpyo(Science Almanac, Tokyo Astronomical Observatory), Bdth (1979), andseveral regional catalogs.In selecting stations for the filming project, it is necessary to adoptseveral stations in the same region, so as not to miss seismograms of anysignificant earthquakes. Finaliy, some problems related to the name, code,and coordinates of seismological stations are discussed.1. IntroductionFirst, it must be emphasized that the seismogram filming project should not beused as justification for: (1) discarding the original seismograms that are selectedfor the filming; and (2) neglecting to keep seismograms at the stations that are notselected for the project. Even the best copies could not replace the original records.Moreover, it is possible that records not selected for the filming will be required inthe future for some unforeseeable scientific or practical needs.Seismograph stations also have to be selected for the filming project. However,seismograms at the stations not selected sometimes become important. Often, astation of high quality failed to record a certain earthquake, but a less qualifiedstation in the same region might succeed in recording it. The information requiredto use the seismograms is expected to be furnished with the copies. However,providing complete information for each seismogram is not easy in many cases.2. Selection of Earthquakes2.1. Magnitudes in Different CatalogsThe common procedure for selecting earthquakes for the seismogram filmingproject is to define significant earthquakes by magnitude and damage. First, westudy the discrepancies of magnitudes in the different standard catalogs. Guten-Hisrorical Seismogramsand Earrhquakes of the World401 Copyright Z IVW by Academic Press, Inc.All rights of reproduction in any form reserved.