Analog Seismogram Archives at the Earthquake Research Institute, the University of Tokyo

Abstract

Abstract The Earthquake Research Institute (ERI) of the University of Tokyo maintains archives of analog seismograms and mareograms. The main collection is ∼236,000 Japanese historical seismograms recorded at the University of Tokyo (at various buildings and using various instruments around Hongo [Tokyo] with a total of 189,000 records from 1881 to 1993), at the Tsukuba observatory (∼11,000 records from 1921 to 1986), and at the Wakayama seismological network (∼12,650 records from 1928 to 1968). Seismograms recorded by temporal stations at various locations in Japan for several years, typically following large earthquakes, are also included. Different types of instruments were used to record the data. The oldest record from a large earthquake is from the 1891 Nobi earthquake recorded at Hongo on a circular seismogram using an Ewing-type seismograph. Teleseismic seismograms include those from the 1899 Alaska earthquake at Hongo on an Omori-type seismograph. Imamura-type and Omori-type tremometers and strong-motion seismographs had also been used for a long time. While these seismograms were microfilmed by the 1990s, the original smoked paper records have also been archived. Foreign seismogram collections include those from earthquakes in Taiwan between 1904 and 1917 recorded in both Japan and Taiwan and those from the Canadian Seismograph Network between 1981 and 1989. For the Worldwide Standardized Seismograph Network stations, almost all (∼5,000,000) microfilm records at 167 stations from 1963 to 1988 are archived. High-resolution image scanning of analog daily seismograms at the Wakayama microearthquake network is currently being performed, and the scans are provided using Leaflet software so that the users can easily access and enlarge parts of seismograms. The tsunami waveform archive contains ∼3100 records on Japanese tide gauges from large earthquakes between 1911 and 1996. The available data, with dates and types of instruments, can be searched from the database through the website of the ERI.