Survey of Geological Structure at Adapazari, The Concentrated Damage Area During 1999 Kocaeli, Turkey, Earthquake

在布格重力异常、微震SPAC和H/V分析以及地震折射测量的基础上，研究了阿塔扎里盆地的基岩结构。主要结果如下：(1)基岩在凹陷边缘逐步下沉；(2)盆地由东西向或北东-南西向三个狭窄的基底凹陷组成。(3)基于重力测量、微地震SPAC和H/V分析以及地震折射测量的结果，建立了阿塔扎里盆地深部地表结构的三维模型；(4)基于三维模型，用有限差分方法对柯凯利地震进行了模拟。结果表明，由于基岩的特殊形态，即聚焦和/或所谓的盆地边缘效应，导致了对城镇造成严重破坏的强烈地震被认为是放大产生的。指出了三维基岩形态的调查是沉积盆地上城市微区划的迫切问题，为此，对重力、微地震和折射波的对比分析具有很高的前景，因为我们可以利用不同的物理参数：地震阻抗和密度分布来获得更可靠的结构模型。研究结果如下：(1)未发现松散沙土层。这一事实表明，在主震期间不会发生典型的液化；(2)瑞典探空仪探测下沉的非常软的土层的厚度在镇上是不同的。认为影响建筑物损伤程度的因素有惯性损伤和沉降型损伤。

The bedrock structure of the basin of Adapazari was studied on the basis of Bouguer gravity anomaly, SPAC and H/V analyses of microseisms, and seismic refraction survey. The main results are as follows :(1)the bedrock subsides stepwise at the edge of depressions ;(2)the basin consists of three narrow depressions of the basement of E-W or NE-SW trending. The depth to bedrock reaches 1000-1500 m ;(3)3D model of deep ground structure of Adapazari basin based on the results of gravity survey, SPAC and H/V analyses of microseisms, and seismic refraction surveys ;(4)simulation of Kocaeli earthquake was performed using Finite Difference method based on the 3D model. The results show that strong motions, which brought severe damage to the town, is considered to have been produced by amplification due to the specific configuration of bedrock, that is, focusing and/or so-called basin-edge effect.It is pointed out that investigation of 3D bedrock configuration is an urgent issue for microzoning an urban area on a sedimentary basin, and for this, comparative analysis of gravity, microseisms and efraction wave is highly prospective, because we can obtain more reliable structural models using different kinds of physical parameters: seismic impedance and density distribution.The surveys of shallow soil profile at the down town was also performed. The results are as follows ;(1)any soil layer of loose sand was not found. This fact shows that typical liquefaction was not considered to occur during the mainshock ;(2)thickness of very soft soil layers, at which probe of Swedish sounding sink by its own weight, varies in the town. It is considered to affect the difference of damage of building between inertia type damage and settlement type damage.