The National Reseach Center for Disaster Prevention (NRCDP) has completed a high quality, digital network for microearthquake and ground tilt observations in the Kanto-Tokai area, Japan. There are 71 stations, including the three deep borehole observatories with depths of from 2300 to 3500 m which the NRCDP completed in 1980 to overcome artificial noise at the surface in and around Tokyo.All data observed is digitized and transmitted through telephone lines to the NRCDP in Tsukuba Science City, about 50 km northeast of the center of Tokyo. Application of new techniques, Automatic Network Timing (ANT) with a high level of accuracy and an error of less than a few m sec, wide dynamic range quantization, 78 dB for seismic data and 96 dB for tilt data, and high density transmission of 9600 bps, is a warranty for high quality which has never been achieved by conventional telemetry systems.Stress is put on quick data processing as a short-term-prediction-oriented system. One computer system, which is directly connected to the telemetry system, carries out the filing of observed data and monitors the crustal activity on a realtime basis. Further data processing steps, such as hypocenter determination by rationalized semi-automatic methods, are executed by the other computer system.Playing an important role in monitoring crustal activity, particularly in the Tokai area where there is an impending earthquake, the present network has been contributing to a variety of studies on seismic activity and tectonics as well as earthquake prediction.
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- A High Quality Digital Network for Microearthquake and Ground Tilt Observations in the Kanto-Tokai Area, Japan
- Springer Netherlands