Determination of Subsurface Structure of Tottori Plain Using Microtremors and Gravity Anomaly
Determination of Subsurface Structure of Tottori Plain Using Microtremors and Gravity Anomaly
复制标题
利用微震和重力异常确定鸟取平原的地下结构
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
R. Nishida
中科院分区：
文献类型：
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作者：
Tatsuya Noguchi;R. Nishida
本研究的目标区域是日本山阴地区的鸟取平原，该地区在1943年鸟取地震（M7.2）中受到严重破坏。严重受损的地区集中在鸟取平原（日本建筑研究所，1944年），而鸟取市西部和南部的破坏较小。这种集中的破坏被认为是由鸟取平原局部地下结构影响的地震地面运动特性造成的。对收集了沉积层钻孔数据的地下剖面（鸟取地下研究所，1991年）进行了调查。等高线图（Akagi等人，1993年）的洪积物和冲积物的基岩已经获得。此外，PS测井（沉积层勘探）和山区弹性波勘探（如，奥约公司，1996年）已完成。重力测量发现，在平原下岩层结构（新近系或古近系地层）的几个点上，存在重力异常。然而，尚未确定详细的密度结构，仅在有限的点上进行了PS测井和弹性波勘探。有两种方法可以确定地下结构。一是利用钻孔资料进行地质剖面的可视化勘探，二是进行物探，获取弹性波速度、勘探密度等物理参数。获得弹性波速度和二维或三维基岩结构的有效方法是微动勘探和重力测量。微震的使用可分为三种类型：使用多个地震仪的阵列观测，在单个站点的三分量观测（单站点观测），以及在土壤和岩石站点的三分量观测。阵列观测记录采用空间自相关（SPAC）或F-K方法进行分析。利用这些方法可以从阵列记录中确定横波速度结构。单点观测记录可以通过水平-垂直谱比（H/V）进行分析。土、岩场地观测记录可以用水平（土场地）与水平（岩场地）的谱比进行分析。在许多地点进行了阵列观测，
The Tottori plain in the Sanin area of Japan, the target area of this study, was severely damaged by the 1943 Tottori earthquake (M7.2). The severely damaged area was concentrated on the Tottori plain (Architectural Institute of Japan, 1944), whereas there was less damage in the western and southern parts of Tottori City. This concentration of damage is thought to have been caused by the characteristics of the earthquake ground motion affected by the local subsurface structure of the Tottori plain. The subsurface cross section (Tottori Subsurface Institutes, 1991) for which borehole data on the sedimentary layer had been collected was investigated. A contour map (Akagi et al., 1993) of the bedrock of the diluvium and alluvium had already been obtained. In addition, PS logging (exploration of the sedimentary layer) and elastic wave exploration of the mountainous area (e.g., Oyo corporation, 1996) has been done. At several points in the rock layer structure beneath the plain (stratum of Neogene system or Paleogene system), gravity anomal was found by a gravity survey. No detailed density structure however has been determined and PS logging and elastic wave exploration have been done only on limited points. There are two ways to determine subsurface structures. One is to visually explore the geologic profile by means of bore-hole data The other is to make a geophysical exploration to obtain physical parameters such as elastic wave velocity and investigating density. Effective methods for obtaining elastic wave velocity and 2D or 3D bedrock structures are microtremor exploration and a gravity survey. The use of microtremors is divisible into three types: array observation using several seismometers, 3-component observation at a single site (single-site observation), and 3-component observation at soil and rock sites. Array observation records are analyzed by the spatial auto correlation (SPAC) or F-K method. The S-wave velocity structure can be determined from array records by these methods. Single-site observation records can be analyzed by means of the horizontal-to-vertical spectral ratio (H/V). Soil and rock site observation records can be analyzed by means of the horizontal- (soil site) - to - horizontal (rock site) spectral ratio. Array observations have been made at many sites in order to