Practical Application of a New exploration Technique Using Microtremors for Reconnaissance Survey to estimate Geological Structure down to a Depth of 3, 000 Meters.

本文介绍了一种利用周期大于1秒的地脉动探测3000米深度地质构造的新技术。由于可以在任何时间、任何地点观测到微震，因此该技术可以比任何其他地震技术更容易、更快、更经济地覆盖给定区域。因此，该技术可用于新勘探区的普查，也可替代常规地震技术，特别是在城市地区。微动本质上是体波和表面波的随机集合，因此我们观察到的微动波形非常复杂，然而，表面波必然在功率上更占优势。本技术利用了这种微震动中表面波的色散特性。本文主要研究地脉动面波相速度的测量问题。 ...更多信息 en发达。数据采集是由这样一个阵列观测系统进行的，该系统同时收集数据，其中由10个地震仪组成的阵列的观测点彼此隔离。使用高精度编码石英钟，数据被单独记录，并在处理时进行关联。由于该系统不需要电缆或无线电传输，因此在阵列设计中获得了很大的灵活性。使用的地震仪是便携式三分量地震仪UP 255（Shindo Giken Co.，有限公司）、在数据处理中，传统的频率-波数谱方法，通过在互谱计算中引入新的AR建模算法，改进了F-K谱分析，将空间自相关法从复杂波列中提取面波的有效方法推广到更高形式的地震计阵列布置中，30阵列测量提供了成功的估计的瑞利波的基模的相速度的高精度。少

A new exploration technique using microtremors with periods longer than 1s has been developed for estimating geological structure to a depth of about 3, 000m. Since microtremors can be observed at any time in any place, the technique makes it possible to cover a given area more easily, quikly, and economically than any other seismic techniques. The technique is, therefore, useful for reconnaissance survey in areas to be newly explored, and also alternative to the conventional seismic techniques especially in urban areas. The microtremor is essentially a random ensemble of body and surface waves, so that the microtremor we observe is very complex in waveform in which, however, the surface waves must be inevitably more predominant in power. The present technique utilizes the dispersion characteristics of the surface waves in such microtremors. The research mainly deals with measurement of phase velocities of surface waves in microtremors, for which data acquisition and processing have be … More en developed. The data acquisition is made by such an array observation system that the data are simultaneously collected for which the observation points of an array consisting of 10 seismometers are isolated from each other. With high-precision coded quartz crystal clocks, the data are recorded separately and correlated at the time of processing. Since the system does not require cable or radio transmission, a great flexibility is attained in array design. The seismometer used is the portable 3-component seismometer UP255 (Shindo Giken Co., Ltd.), its natural period being reset from 1s to 8s.For the data processing, the traditionally used frequency-wavenumber spectrum (F-K spectrum) analysis is improved by introducing a new AR-modeling algorithm into calculation of cross-spectrums, and the spatial autocorrelation method efficient to detection of surface waves from complex wave train is extended to a higher form in arrangement of seismometer array.The new technique examined about more than 30 array measurements provided successful estimation of the phase velocity of the fundamental mode of Rayleigh waves with high accuracy. Less