Co-seismic Displacements of the 1995 Hyogo-ken Nanbu Earthquake
Co-seismic Displacements of the 1995 Hyogo-ken Nanbu Earthquake
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1995 年兵库县南部地震的同震位移
DOI：
10.4294/jpe1952.44.255
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
T. Tada
中科院分区：
文献类型：
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作者：
M. Hashimoto;T. Sagiya;H. Tsuji;Y. Hatanaka;T. Tada
本文介绍了1995年1月17日兵库县南部地震的同震位移，它是由GPS（全球定位系统）连续观测、运动型GPS测量和水准测量所探测到的。连续的GPS观测给出了一个一致的模式的位移与那些预期的从右侧滑动的NE-SW走向的垂直断层在远场：约50公里的震中东和西的站向震中移动了约4厘米，而站北和南移动远离震中。通过与10年前的经纬仪测得的测线长度进行比较，发现淡路岛上的大部分控制点都向西南或南部移动，这可能是由于切断地表的野岛断层的运动。另一方面，在科比及其周边地区，六甲断层系统西北方向的控制点向东北方向移动，而另一侧的控制点则略微向西移动。水准测量数据显示，六甲断层系统的一个成员-苏马断层西北侧隆起19厘米，而该断层以东下沉7厘米。此外，在科比市的中部观察到约5厘米的隆起，在科比以东检测到5厘米的沉降。野岛断层北方延伸段的水平位移和垂直位移没有明显的空区，表明该次地震的破裂过程较为复杂。淡路岛东海岸的水准测量显示，在过去20年中，该隆起区域的两个边缘都有轻微的沉降，但隆起约20 cm。通过拟合上述大地测量数据，我们寻找了一组最佳的位错模型参数。根据余震分布和震源机制，我们假定从科比到淡路岛有6条近垂直的NE-SW向断层。淡路岛断层约250 cm左右的右旋滑移是由野岛断层附近的大水平位移引起的。科比断层可被一个与余震群大致对应的无滑移带分为两段，其滑移量为100-200 cm。野岛断层的南部、明石海峡附近和科比中部以北可能有100 cm的大推力分量。我们还研究了在严重破坏区下方存在埋藏断层的可能性。由于该模型不能解释观测到的大地测量数据，估计的滑动与震源机制不一致，这些可能的隐伏断层可能不会发挥重要作用，如果有的话。
We present co-seismic displacements of the Hyogo-ken Nanbu earthquake of January 17, 1995, detected by continuous GPS (Global Positioning System) observation, campaign type GPS survey and leveling. Continuous GPS observation gives a consistent pattern of displacements with those expected from a right lateral slip on a NE-SW trending vertical fault in far field: stations about 50 km east and west of the epicenter moved toward the epicenter by about 4 cm, while stations north and south moved away from the epicenter. By comparing with line lengths obtained by geodolite about 10 years ago, the campaign type GPS revealed most control points on Awaji Island moved to the southwest or south, which may be attributed to the movement of the Nojima Fault which cut the surface. On the other hand, control points northwest of the Rokko fault system moved toward the northeast and those on the other side moved slightly to the west, in and around Kobe. Leveling data revealed uplift of 19 cm on the northwestern side of the Suma Fault, a member of the Rokko fault system, and subsidence of 7 cm just east of this fault. Furthermore, uplift of about 5 cm was observed in the central part of Kobe City, and subsidence of 5 cm was detected east of Kobe. There is no significant gap in horizontal and vertical displacements around the northern extension of the Nojima Fault, which implies a complicated rupture process of this event. Leveling on the east coast of Awaji Island revealed a significant uplift of about 20 cm with slight subsidence at both edges of this uplift region during the past 20 years. By fitting the above geodetic data, we searched for an optimal set of parameters of a dislocation model. We assumed six nearly vertical faults trending NE-SW from Kobe to Awaji Island on the basis of aftershock distribution and focal mechanism. About 250 cm of the right lateral slip for the fault on Awaji Island is derived from large horizontal displacements near the Nojima Fault. The fault in Kobe may be divided into two segments with 100-200 cm slip by a slip-free zone which roughly corresponds to the cluster of aftershocks. The southern part of the Nojima Fault, segments near the Akashi Strait, and north of central Kobe may have significantly large thrust components of 100 cm. We also examined the possibility of buried faults beneath the zones of severe damage. Since this model cannot explain the observed geodetic data and the estimated slips are inconsistent with focal mechanism, these possible buried faults may not play a significant role, if any.