MULTIDISCIPLINARY RESEARCH ON FAULT ACTIVITY IN THE WESTERN PART OF THE NORTH ANATOLIAN FAULT ZONE

北安纳托利亚断裂带西部存在一个地震空区，该断裂在地震空区分为两个分支，北方分支具有宽的地堑状构造，而南分支显示为右旋走滑型活动断层，我们称南分支为伊兹尼克-我们建立了一个当地的地震观测网，并进行了临时观测，发现伊兹尼克断层的地震活动很低，Mekece断层。这与北方分支的高地震活动性相反，在那里间歇性地震群也很明显。Iznik-Mekece断层目前可能处于第二类地震空区的稳定状态。在小的短暂河流的通道处进行了挖沟，显示出一个右-约40米的台阶偏差。表层土壤以下的地层由崩积层组成，崩积层下面是厚的泥石流沉积物。上部崩积层没有受到任何扰动，而下部崩积层和泥流层则与Iznik断层有关，取自未扰动层的标本显示其年代约为200年前，在断层扰动的崩积层底部附近发现了一个距今约500年的样品，推断该断层最近一次大地震发生在距今200-500年之间。持续监测可能的地磁变化是重要的。我们开始持续测量地磁总强度和自电位。还定期测量地下水的化学成分和土壤气体中的氡浓度。

There exists a saismic gap in the western part of the North Anatolian Fault Zone.This fault is separated into two branches in the seismic gap area.The northern branch is characterized by a wide,graben-like structure, while the southern branch shows an active fault of right-lateral strike-slip type.We call the southern branch the Iznik-Mekece fault.We established a local seimsmic observation network and made temporary observations found that seismic activiry is very low at the Iznik-Mekece fault.This is wuite contrary to high seismicity at the northern branch where intermittent earthquake swarms are also notable.The Iznik-Mekece fault may currently be at the stabe of seismic gap of the second kind.Trenching was made at the channel of the small ephemeral stream showing a right-step defiection of about forty meters.The layer below surface soil is composed of colluvium deposits which are underlain by thick mud-flow deposits.The upper colluvium layer has not suffered any disturbances, whereas the lower colluvium layer and the mud-flow layer were disturbed in association with faulting on the Iznik-Mekece fault.The spcimens taken from the umdisturbed layer show the date of about 200 years B.P., indicating that no significant faulting has taken place since 200 years B.P. One specimen specimen showing about 500 years B.P. was found near the bottom of the colluvium laver which suffered disturbances due to faulting.It is concluded that the latest large earthquake at this fault must have taken place 200-500 years B.P.For earthquake prediction studies,continuous monitoring of possible precursoy changes is important.We started continuous measurements of geomagnetic total intensiry and self-potential.Chemical components of groundwater and radon concentration in soil gas have also been measured routinely.