Distribution of precarious rocks at the Nevada Test Site: Comparison with ground motion predictions from nuclear tests
Distribution of precarious rocks at the Nevada Test Site: Comparison with ground motion predictions from nuclear tests
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内华达试验场不稳定岩石的分布：与核试验地面运动预测的比较
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
A. Anooshehpoor
中科院分区：
文献类型：
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作者：
J. Brune;D. V. Seggern;A. Anooshehpoor
[1] 不稳定的岩石被认为是已经存在了数千年的地动地震仪，从而为地震灾害估计提供了重要的限制。内华达试验场 (NTS) 的大型核爆炸区域存在许多不稳定的岩石。核试验的地面运动记录提供了地面加速度和地面速度与距离和爆炸当量的函数关系的回归方程，以便与不稳定岩石的约束进行比较。非常靠近大型 NTS 爆炸，没有不稳定的岩石或半不稳定的岩石。悬崖面被破碎，许多最近的落石表面覆盖着钙质，这证明落石是由爆炸引起的。随着距爆炸的距离增加和预测的地面运动轮廓减小，观察到的落石越来越少，一些半不稳定的岩石开始出现，最后，发现了大量不稳定的岩石，但没有近期落石的证据。为了量化不稳定岩石和地面运动的校准，我们（1）对岩石进行现场测试以确定准静态和动态倾倒加速度，（2）使用 NTS 爆炸波形的估计进行计算机测试，以及（3）将结果与核爆炸经验回归预测的地面运动进行比较。我们的结论是，这些比较为不稳定岩石方法提供了重要验证，并为倾覆加速度的初步估计提供了近似验证。
[1] Precarious rocks have been proposed as ground motion seismoscopes that have been in place thousands of years, thereby providing important constraints on seismic hazard estimates. Numerous precarious rocks exist in the region of large nuclear explosions at Nevada Test Site (NTS). Ground motion recordings from nuclear tests have provided regression equations for ground acceleration and ground velocity as a function of distance and explosion yield for comparison with constraints from precarious rocks. Very near large NTS explosions, there are no precarious rocks or semiprecarious rocks. Cliff faces are shattered and numerous recent rockfalls have fresh white surfaces covered by caliche: proof that the rockfalls have been caused by the explosions. As the distance from the explosions increases and the contours for predicted ground motion decrease, fewer and fewer rockfalls are observed, some semiprecarious rocks begin to appear, and finally, numerous precarious rocks are found with no evidence of recent rockfalls. To quantify the calibration of precarious rocks and ground motion we (1) do field tests on the rocks to determine the quasi-static and dynamic toppling accelerations, (2) carry out computer tests using estimates of waveforms from NTS explosions, and (3) compare the results with ground motions predicted by empirical regressions for nuclear explosions. We conclude that these comparisons provide an important validation of the precarious rock methodology and an approximate validation of preliminary estimates of toppling accelerations.