Research on Fault Activity in the North Anatolian Fault Zone

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The North Anatolian fault zone elongated in the east-west direction in northern Turkey has been considered a test field for earthquake prediction studies, because there exists a so-called seismic gap. The purpose of this project is to investigate the characteristics of earthquake generation through intensive surveys of active faults, as part of basic researches on earthquake prediction.We have so far made various kinds of surveys ; seismic observations, gravity observations, geomorphological studies of active faults, geomagnetic and electric observations. The outline of these surveys is as follows.(1) Seismic observationIn order to monitor microseismic activity in the gap area, we have established a radio-linked seismic observation system consisting of a base station, where a three- component seismometer was set up, and five satellite stations, where a vertical-component seismometer was installed. It was found from the observations that some microearthquakes have been occurring in the gap area.(2) Gravity surveyA precise gravity survey network was established across active faults and the first survey was made. A similar survey must be carried out in the near future to monitor crystal movement in the survey area.(3) Continuous strain measurementA precise strainmeter was installed at a station located very close to an active fault to monitor a possible strain change associated with fault displacement.(4) Continuous geomagnetic and electric measurementsSeven geomagnetic and two electric stations have been in operation to monitor possible changes in the geomagnetic and electric fields associated with earthquakes in the test field.(5) Geomorphological studyExtensive geomorphological studies were made in the western part of the North Anatolian fault zone, and the cumulative amount of fault displacement could be estimated.