Investigation of Strong Ground Motion around MTL in Mikawa Area

丰桥工业大学强震观测阵列系统（TASSEM）是在丰桥市周围开发的，目的是观测该地区的强震，并调查断层等地质和地形条件的影响。地震观测及其数值分析如下所述进行。a）除了1989年建立的旧观测点（TUT周围称为站点1）之外，还于1995年在新城市（称为外部区域站点2）和蒲郡市（称为内部区域站点3）建立了强震仪。这些观测点均分布在中央构造线（MTL）周围，工程意义上设置在基底上。共观测到5次地震记录，其中4次发生在外区，1次发生在内区。B）通过对这些记录的加速度的分析，发现由于MTL内的散射，波的传播具有明显的不稳定性， ...更多信息 在地震动的放大和衰减方面，虽然有些记录显示出地震波在MTL上传播时有放大高频分量的趋势，但仅从MTL效应的角度很难断言这种结果，因为我们需要将地形条件的局部场地效应与近场土壤条件分开。另一方面，在海滨地区，无论是内区还是外区，都观测到了放大现象，这可能是由于厚冲积层的影响。d）不同观测点的相干函数在不同的震源区表现出不同的值。地震动的理论分析表明，场地条件对地震动的放大作用是显著的，但作为波传播衰减指标的MTL两侧Q值差异不大。更准确的模拟必须进行实验，以impret MTL效应。少

The TASSEM,Toyohashi University of Technology Array System for Strong Earthquake Motions, has been developed around Toyohashi city to observe the strong ground motions of this area and investigate the effects of geological and topographical conditions including fault existence. The earthquake observations and their numerical analysis were conducted as remarked as below.a) The strong motion seismograph has been set up in Shinshiro city (called site 2 in outer zone) and Gamagori city (called site 3 in inner zone) in 1995, in addition to old observation points (called site 1 around TUT) established in 1989. All these observation location are distributed around the Median Tectonic Line (MTL) and installed on the basement in engineering meaning. In total, five earthquake records were observed, four of which occurred in outer zone and one in inner.b) Based on the analysis of such recorded acceleration, unsteady properties of wave propagation due to the scattering within MTL are obvious, that … More are involved with the ratation of principal propagating direction and the occurrence of additional surface wave and different frequency distribution within inner zone and outer zone.c) On the amplification and attenuation of ground motions, even though some records showed trend to amplify the high frequency components when the seismic wave propagated over the MTL,it is difficult to assert such results only from MTL effect, because we need to separate the local site effect of topographical conditions besidea near field soil condition. On the other hand, the amplification in seaside area were always observed both in inner zone and outer zone, which is considered due to the effects of thick alluvium.d) The coherency functions of different observation sites showed various value with respect to different focal region. It is considered that both MTL and site effects on ground motions behaved associated with seismic wave propagating routes.e)The theoretical analysis on ground motion indicated that the amplification due to local site conditions was significant, but the Q value in both side of MTL,as an index of attenuation of wave propagation, showed no much difference. More accurate simulations have to be experimented to imterpret the MTL effects. Less