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

438 Y. Tarnura, H. Sasaki, M. Ooe, and K. Hosoyama3. New Filming ProjectOur original filming project was carried out using only the seismographs whichregistered large earthquakes. We selected a 70-mm film format to ensure highresolutioncopies. The actual operations were carried out by an expert commerciallaboratory, even though the cost was rather expensive. This project was possiblebecause the number of filmed records was only about 10% of all the observedseismograms.Now we are carrying out a new filming project for all seismograms on 35-mm filmaccording to the recommendations of IASPEI. About 60,000 seismograms, includingthose on which no earthquake is recorded, will be filmed. This project requires abudget larger than 5 million yen.As the 35-mm film size is rather small compared to the original record, we haveselected the copying film carefully, finally choosing Kodak’s Technical Pan 2415film and Technidol LC developer. This film has fine granules and high resolution inspite of its 35-mm size, and the developer provides moderate contrast for smokedpaperrecords. The filmed records have at least 0.2-mm resolution and can be usedto measure amplitude to f 0.1 mm and time to f 0.1 sec when enlarged to theiroriginal size. The reduction scale is about 1/20. The above resolution may benecessary to measure arrival times and to digitize the waveforms.We hope that these filming procedures will safely preserve these valuable seismograms.All data in the ILOM will be available to any researcher for studies ofhistorical earthquakes.REFERENCESFtika Nenpyo (Chronological Scientific Tables) (1975). geophysical part, pp. 181-212, ed.Tokyo Astronomical Observatory, Maruzen Co., Ltd.Rika Nenpyo (Chronological Scientific Tables) (1981). geophysical part, pp. 204-221, ed.Tokyo Astronomical Observatory, Maruzen Co., Ltd.Seismological Observations at Mizusawa for the Period between 1902-1967 (1984). Int.Latit. Obe. Mizusawa.