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已经证实,在一条条路径上传播的Lg震相,以全球的m_b震级和核爆当量作为其相对标度,有着不寻常的稳定性和精度。然而,有着一定震级的Lg的定标斜率,在不同的传播路径上时常存在相当大的差别,这些不好解释的效应常纠缠到核监测过程。本文通过资料分析和数字模拟,揭示影响Lg定标的因素。分析了前苏联巴拉潘的核试验场的爆破在欧亚宽频带地震台的数字地震资料。该资料得出,震源谱的当量定标与每一传播路径上的频率选择特性的结合,可反映观测到的定标斜率的变化。由于衰减而引起的高频能的损失导致沿某些路径的定标斜率偏高。场地效应和仪器响应中的变化也能够对Lg定标斜率的分散产生影响。用于计算理论定标率的数字模拟,支持了这些论断。
It has been demonstrated that the Lg seismic phase propagating on a single path has unusual stability and accuracy with its global m_b magnitude and nuclear explosion equivalent as its relative scale. However, the calibration slopes of Lg with a certain magnitude often have quite different differences in propagation paths, and these poorly explained effects often entangle the nuclear monitoring process. In this paper, data analysis and numerical simulation revealed the factors that affect Lg calibration. The digital seismic data of the Eurasian broadband seismic station during the blasting of the nuclear test site in Ballapan of the former Soviet Union was analyzed. This data shows that the combination of the equivalent calibration of the source spectrum with the frequency-selective characteristics on each propagation path can reflect the observed change in the calibration slope. The loss of high frequency energy due to attenuation leads to a high calibration slope along certain paths. Changes in site effects and instrumental responses can also affect the dispersion of the slope of the Lg calibration. The numerical simulations used to calculate the theoretical scaling rate support these assertions.