Research on Fault Activity in the North Anatolian Fault Zone

土耳其北部东西方向延伸的北安那托利亚断裂带被认为是地震预测研究的试验场，因为那里存在所谓的地震间隙。本项目的目的是通过密集的活动断层调查来研究地震发生的特征，作为地震预测基础研究的一部分。到目前为止，我们进行了各种各样的调查；地震观测、重力观测、活动断层地貌学研究、地磁和电观测。这些调查的概要如下。(1)地震观测为监测断裂带微震活动，我们建立了由1个基站和5个卫星站组成的无线电连接地震观测系统，基站分别设置了1台三分量地震仪和1台垂直分量地震仪。从观测中发现，在断裂带内发生了一些微地震。(2)重力测量在活动断层上建立了精密重力测量网，并进行了首次测量。在不久的将来，必须进行类似的调查，以监测调查区域的晶体运动。(3)连续应变测量在离活动断层非常近的站点安装了精密应变仪，以监测断层位移可能引起的应变变化。(4)连续地磁和电测量7个地磁站和2个电场站已投入运行，以监测试验场与地震有关的地磁场和电场的可能变化。(5)地貌研究：对北安那托利亚断裂带西部进行了广泛的地貌研究，估算了断层的累计位移量。

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.