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

426 Kezin QuTable 1. Seismogram Statistics from the Sheshan and Dalian StationsDalian StationInstrument type Time of operation Number of Monthly(year.month) seismograms aver ageOmori* 1904 - 1943 301 1 .oWiechert 1930 - 1945 304 1.68Type 51 1955.08 - 1955.11 179 44.81956.01 - 1963.12 2920 601964.01 - 1965.09 243 11.6Kirnos 1967.01 - 1970.12 1460 601971.01 - 1971.12 35 2.9Sheshan StationOmori 1904.01 - 1918.09 2380 13.4Wiechert 1909.04 - 1950.03 4900 10.2G alit zin 1915.04 - 1949.04 2789 6.8Galitzin 1954.01 - 1956.09 701 21.2Galit zin- Wilip 1932.04 - 1936.03 857 18.2Wiechert 1950.04 - 1970 8518 36.1G alitzin- Wilip 1950.08 - 1966.12 3406 17.3K’ rnos 1956.02 - 1981.12 10249 33.0Type 54 1954.12 - 1957.06 770 17.9Type 64 1969.08 - 1975.11 3206 42.2DD- 1 1973.07 - 1981.12 3643 35.7(*) = The Omori seismograms are for the years 1918-1943.7. ProgressSeismogram microfilming is undoubtedly an important factor in the establishmentof a worldwide seismic database. Our work on the microfilming of seismograms wasintroduced briefly at the Tokyo Workshop in 1982 (Qu, 1982).The work can be divided into two parts: (1) data sorting and labelling; and(2) microfilming. Seismic data sorting includes three parts: (a) Seismograms -the station code, recording date, and types of instruments are checked and thenlabelled on each seismogram. The Institute of Geophysics collects and sorts eachrecord. As the seismogram storage place and the office in charge has changed manytimes, identification of historical seismograms is both difficult and time-consuming.(b) Seismograph parameters - the seismograph parameters and timing system ofeach st ation are checked and registered according to types of seismographs anddifferent periods of recording. (c) The seismological bulletins compiled by individualstations are inventoried and sorted. After microfilming and careful checking, theseismograms are filed in chronological order.Data sorting is completed at the Institute of Geophysics, State SeismologicalBureau, and the Seismological Bureaus of Gansu, Yunnan, Jiangsu, and Shanghai