Research on Fault Activity in the North Anatolian Fault Zone

土耳其北方东西向伸展的北安纳托利亚断裂带存在着一个所谓的地震空区，因而被认为是地震预报研究的试验场。本项目的目的是作为地震预报基础研究的一部分，通过对活动断层的深入调查，研究地震的发震特征。迄今为止，我们进行了地震观测、重力观测、活动断层地貌研究、地磁观测和电观测等各种各样的调查。这些调查的概要如下。(1)地震观测为了监测差距地区的微震活动，我们建立了一个无线电连接的地震观测系统，该系统由一个基站和五个卫星站组成，基站上安装了一个三分量地震仪，卫星站上安装了一个垂直分量地震仪。观测结果表明，在差距地区有微地震发生。(2)重力测量建立了跨活动断裂的精密重力测量网，并进行了首次重力测量。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)连续应变测量精密应变仪安装在非常靠近活动断层的站点，以监测与断层位移相关的可能应变变化。(4)连续的地磁和电场测量七个地磁站和两个电场站已经投入运行，以监测与试验场地震有关的地磁场和电场的可能变化。(5)地貌研究在北安纳托利亚断裂带的西部进行了广泛的地貌研究，可以估计断层位移的累积量。

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.