Three-dimensional topography of the sediment/basement interface in the Tokyo metropolitan area, central Japan
Three-dimensional topography of the sediment/basement interface in the Tokyo metropolitan area, central Japan
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日本中部东京都市区沉积物/基底界面的三维地形
DOI：
10.1785/bssa0820062328
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发表时间：
1992
影响因子：
3
通讯作者：
S. Higashi
中科院分区：
文献类型：
--
作者：
K. Koketsu;S. Higashi
在日本中部的东京大都市地区进行了广泛的地震折射实验，以揭示该地区的三维盆地结构在14年内发射了14年。
对于我们的反转，地下室被认为是两个均匀的区域，假定沉积物的速度均匀。在解决方案中。在层状上，界面的形状很好地确定了其他地球物理调查的结果，例如井眼测量和重量观测值。
先前的二维分析表明，在南部地下室的最高部分中有4.5 km/sec的层，但我们以简单的态度忽略了它，因此，在南部地区，估计的深度可能被1到2公里低估了提供该地区盆地结构的第一个详细图像，这将有助于强烈的运动和地震危险研究作为其他约束。
An extensive seismic refraction experiment was conducted in the Tokyo metropolitan area, central Japan, to reveal the three-dimensional basin structure in this area. Sixty-three explosions were fired over 14 years and more than 2000 travel times were picked for several phases.
For our inversion, the basement is divided into two homogeneous regions where the sediment is assumed to be of uniform velocity. The interface separating the sediment and basement is then parameterized by bi-cubic B-splines and a smoothness constraint is imposed to avoid oscillatory artifacts in the solution. The relative weight of the constraint to data residuals is determined by minimizing Akaike's Bayesian information criterion. About 1500 travel times of refracted P waves are inverted tomographically, and the interface shape determined agrees well with the results of other geophysical surveys such as borehole measurements and gravimetric observations. The basement velocities in the northern and southern regions are 5.7 and 5.4 km/sec, respectively.
Previous two-dimensional analyses suggested there is a 4.5 km/sec layer in the uppermost part of the southern basement, but we ignore it for simplicity so that estimated depths are likely underestimated by 1 ∼ 2 km in the southern region. Nevertheless, this study provides the first detailed image of the basin structure in the area, which will help strong motion and earthquake hazard studies as additional constraints.