3 dimensinal structure and history of seismic Janlt of 1923 type Kanto Earthqnakc

相模湾位于北美板块和菲律宾海板块的交界处，具有独特的地质构造背景。在相模湾，北美板块的特征是非火山岩，与几个小圆丘和银行平行的边界对齐。其形态不象中村（1986）所认为的张性构造，而象挤压构造。另一方面，菲律宾海板块以火山碎屑岩为特征，除舞鹤穹丘外，没有发现明显的挤压变形构造。在海湾西南部的伊豆半岛上沿着可见到一些单生火山。北美板块;在MCS（多道地震）剖面上识别出与板块边界有关的反转断层和褶皱。东京峡谷穿越板块边界的深拖啁啾声纳剖面也揭示了表层沉积物的弯曲 ...更多信息 这表明变形是相当活跃的。因为东京峡谷的沉积率估计非常高。OBS测量得到的地壳深部结构显示，板块边界以西存在向东倾斜的层状结构，边界处存在地壳不连续性。我们认为这个不连续面是由逆断层形成的。此外，Izanagi海底图像显示了发育良好的冲沟结构，特别是在非火山岩丘和河岸的西南边缘。我们认为，水力冲断是假设发生在欧亚板块的西南边缘，由于高孔隙压力，引起的菲律宾海板块俯冲到北美板块之下。菲律宾海板块;横穿Manazuru山丘的MCS剖面显示Manazuru山丘南缘存在向北倾斜的逆冲断层。OBS数据支持MCS剖面的解释。根据Izanagi数据获得的线性构造和潜水观测发现的蛤群的线性分布，确定了沿着伊豆半岛的NNW-SSE趋势的其他主要断层。由岩墙空间分布确定的sigma Hmax为NNW，表明存在左旋走滑断层，走向为NNW-SSE。我们解释单成因火山的岩浆假设为沿着断层侵入，因为单成因火山分布靠近断层。

Sagami Bay is quite unique in terms of geo-tectonic setting, becasuse it locates on the plate boundary between the North-American and the Philippine Sea plates. In the Sagami Bay, the North-American plate is charcterized by non-volcanic terrane with alignment of several knolls and banks, parallel to the boundary. The morphology seems to represent compressional tectonis feature rather than tentioaal one as was proposed by Nakamura (1986). On the other hand, the Philippine Sea plate is characterized by volcanic terrane and no distinct structure characterized by compressional deformatiom is identified on the Philippine Sea plate except Maizuru Knoll. Some monogenic volcanoes are seen along the Izu Peninsula in south-western part of the bay.North-American Plate ;Revease faults and folding in relation to plate boundary are identified on the MCS (multichannel seismic) profiles. Deep tow chirp sonar profile from the Tokyo Canyon crossing plate boundary, also, reveals flexture of surface sedim … More ents, suggesting that the deformation is quite active. Because the sedimentation rate in the Tokyo Canyon is estimated to be very high. Deep crustal structure obtained by OBS survey shows eastward dipping layr west of the plate boundary and crustal discontinuity at the boubary. We interprete the discontinuity to be formed by reverse fault. Moreover Izanagi sea floore image shows well developed gully structure, particularly on the southwestern margin of knolls and bank in non-vocanic terrane. We interprete that hydroflucturing is assumed to occur on the southwestern margin of the Eurasian plate due to high pore pressure, induced by underthrusting of the Philippine Sea plate below the North-American plate. Consequently, we can conclude that the plate boundary between the North-Americn and Philippine Sea plates is convergent margin.Philippine Sea palte ;The MCS profile runnig across the Manazuru knoll shows thrust faults at the southern margin of the Manazuru knoll dipping to the north. OBS data support the interpretation of MCS profile. Additional major fault is identified with a trend of NNW-SSE along the Izu Peninsula based on lineament obtained by Izanagi data and linear distribution of clam colonies found out by diving observation. sigma Hmax determined by spatial distribution of dykes is NNW,suggesting the occurrence of left lateral strike-slip fault with a trend of NNW-SSE.We interprete Magmas of monogenic volcanoes is assumed to intrude along the fault, because the monogenic volcanoes distribute close to the fault Less