Multidisciplinary Research on Fault Activity in the Western Part of the North Anatolian Fault Zone (The Second Phase)

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The aim of this research is to investigate fault activity in the western part of the North Anatolian Fault Zone. First we made seismic observations to examine microseismic activity in the so-called seismic gap area. The result of observations at 9 stations during three months indicates that seismic activity is very low at the southern section, whereas activity is high in the northern section. We also made a trenching work in order to reveal the recurrence rate of major earthquakes. It turned out that major earthquakes occur every 300-400 years. This rate is extremely short compared with active faults in Japan. Geomorphological work also delincated the extension of an active fault which has so far been vague. Electric and magnctic work disclosed anomalies associated with fault structure and based on the anomalies, continuous measurements of the geomagnetic field has been made at 7 stations. So far slight anomalous changes seem to have been detected in association with slight increase in seismic energy. Continuous electric measurements have also been made in the vicinity of the fault. Radon concentration in soil gas has been monitored routinely at some sites near the active fault. We complied these results in a report. We have been requested to send copies of this report to scientists over the world since we reported the results at an international meeting on earthquake prediction.