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Shallow Velocity Structure at the Shagan River Test Site in Kazakhstan

机译：哈萨克斯坦沙干河试验场的浅层速度结构

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摘要

— During 1997 and 1998, twelve chemical explosions were detonated in boreholes at the former Soviet nuclear test site near the Shagan River (STS) in Kazakhstan. The depths of these explosions ranged from 2.5 to 550 m, while the explosive yield varied from 2 to 25 tons. The purpose of these explosions was for closure of the unused boreholes at STS, and each explosion was recorded at local distances by a network of seismometers operated by Los Alamos National Laboratory and the Institute of Geophysics for the National Nuclear Center (NNC). Short-period, fundamental-mode Rayleigh waves (Rg) were generated by these explosions and recorded at the local stations, resultingly the waves exhibited normal dispersion between 0.2 and 3 seconds. Dispersion curves were generated for each propagation path using the Multiple Filter Analysis and Phase Match Filtering techniques. Tomographic maps of Rg group velocity were constructed and show a zone of relatively high velocities for the southwestern (SW) region of the test site and slow propagation for the northeastern (NE) region. For 0.5 sec Rg, the regions are separated by the 2.1 km/sec contour, as propagation in the SW is greater than 2.1 km/sec and less in the NE region. At 1.0 sec period, the 2.3 km/sec contour separates the two regions. Finally, for 1.5 and 2.0 sec, the separation between the two regions is less distinct as velocities in the NE section begin to approach the SW except for a low velocity region (<2.1 km/sec) near the center of the test site. Local geologic structure may explain the different regions as the SW region is composed predominantly of crystalline intrusive rocks, while the NE region consists of alluvium, tuff deposits, and Paleozoic sedimentary rocks. Low velocities are also observed along the Shagan River as it passes through the SW region of the test site for shorter period Rg (0.5–1.0 sec). Iterative, least-squares inversions of the Rg group velocity dispersion curves show shear-wave velocities for the southwestern section that are on average 0.4 km/sec higher than the NE region. At depths greater than 1.5 km the statistical difference between the models is no longer significant. The observed group velocities and different velocity structures correlate with P-wave complexity and with spatial patterns of magnitude residuals observed from nuclear explosions at STS, and may help to evaluate the mechanisms behind those observations.
机译：—在1997年和1998年期间，哈萨克斯坦沙干河（STS）附近的前苏联核试验场的井眼中发生了12次化学爆炸。这些爆炸的深度范围从2.5到550 m，而炸药的产量从2到25吨不等。这些爆炸的目的是为了关闭STS上未使用的钻孔，并且每次爆炸都是通过洛斯阿拉莫斯国家实验室和国家核中心地球物理研究所（NNC）运作的地震仪网络在局部距离上记录的。这些爆炸产生了短周期的基模瑞利波（Rg）并记录在本地台站，结果这些波在0.2到3秒之间表现出正常的色散。使用多重滤波器分析和相位匹配滤波技术为每个传播路径生成了色散曲线。构造了Rg群速度的断层扫描图，并显示了测试地点的西南（SW）区域相对较高的速度区域以及东北（NE）区域的较慢传播区域。对于0.5秒的Rg，区域之间的距离为2.1 km / sec，因为西南地区的传播速度大于2.1 km / sec，而NE地区的传播速度较小。在1.0秒的时间段内，2.3 km / sec的轮廓将两个区域分开。最后，在1.5和2.0秒内，两个区域之间的间隔不太明显，因为NE区域中的速度开始接近西南，除了靠近测试地点中心的低速区域（<2.1 km / sec）。西南部地区主要由晶体侵入岩组成，而东北地区则由冲积层，凝灰岩沉积层和古生代沉积岩组成，当地的地质结构可能解释了不同的区域。在沙干河沿较短的Rg时间（0.5-1.0秒）穿过试验区的西南地区时，也观察到了较低的速度。 Rg组速度弥散曲线的迭代最小二乘法反演表明，西南剖面的剪切波速度平均比东北地区高0.4 km / sec。在大于1.5 km的深度处，模型之间的统计差异不再显着。观测到的群速度和不同的速度结构与P波的复杂性以及STS核爆炸观测到的震级残量的空间格局有关，可能有助于评估这些观测背后的机制。

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  • 来源
    《Pure and Applied Geophysics》 |2001年第11期|2017-2039|共23页
  • 作者

    J. L. Bonner; D. C. Pearson; W. S. Phillips; S. R. Taylor;

  • 作者单位

    Southern Methodist University Dept. of Geological Sciences P.O. Box 0395 Dallas TX 75275 U.S.A. E-mail: bonner@passion.isem.smu.edu;

    Los Alamos National Laboratory EES-3 MS C335 Los Alamos NM 87545 U.S.A. E-mails: cpearson@lanl.gov wsp@lanl.gov taylor@lanl.gov;

    Los Alamos National Laboratory EES-3 MS C335 Los Alamos NM 87545 U.S.A. E-mails: cpearson@lanl.gov wsp@lanl.gov taylor@lanl.gov;

    Los Alamos National Laboratory EES-3 MS C335 Los Alamos NM 87545 U.S.A. E-mails: cpearson@lanl.gov wsp@lanl.gov taylor@lanl.gov;

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  • 正文语种 eng
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  • 关键词

    Key words: Rg; shear wave velocity structure; Shagan River Test Site.;

    机译：关键字：Rg;剪切波速度结构沙干河试验场。;

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