South Kanto Monitoring Chain on Crustal Activities and Its Processing System of Multi-Dimensional Data

Abstract

The group of university scientists in crustal movement studies has constructed a series of Monitoring Chains on Crustal Activities (MOCCA) in Japan. The Chain is a concentrated station system for monitoring of crustal activities along a belt, which crosses areas of seismotectonic importance in such a way as to involve the existing observatories and principal routes of geodetic surveys. Each Chain is about 150 km long with 8–10 multi-purpose stations at average separation of 15–20 km. The close spacing of stations will allow our cross-correlational discrimination of the seismic precursory signals which might originate from the interior of the earth’s crust.

The Chain in the South Kanto district operated by the Earthquake Research Institute takes a route from Suruga Bay to Tokyo Bay, crossing the northern extension of the Suruga and Sagami Troughs. Each of the eight stations are equipped with borehole tiltmeters and wide-band seismographs (vertical component), and each station has several auxiliary channels available for data collection from other geophysical instruments. The system employs an ordinary telephone line for the store-and-forward system of data. The local stations are polled every hour automatically by the control station at Tokyo, where the daily report is obtained at the end of the day. Seismic channels are triggered only when an earthquake is detected. All the data are stored in an editing file at the control station and are later transferred to permanent files on magnetic floppy disks for further analyses.

The central system is supported by a subsystem consisting of a desk-top computer, which assists our searching the multi-dimensional data domain for seismic precursory anomalies. Test experiments have proved its usefulness for efficient processing of large-size multi-dimensional data of crustal activities.