APPLICATION OF PHASED ARRAYS TO ANALYSIS OF SEISMIC BODY WAVES
APPLICATION OF PHASED ARRAYS TO ANALYSIS OF SEISMIC BODY WAVES
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DOI：
10.1098/rsta.1965.0048
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发表时间：
1965-01-01
影响因子：
--
通讯作者：
WHITEWAY, FE
中科院分区：
文献类型：
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作者：
BIRTILL, JW;WHITEWAY, FE
地震仪阵列的间隔距离与信号的最长视波长相当，已用于通过速度滤波过程促进地震震相的分离和识别。阵列中的各个地震仪被记录在磁带的单独磁道上，并且在回放时通过插入时间延迟来求和以消除所需信号的传播延迟。插入的延迟具有将阵列调谐到所需速度和方位的效果，从而区分不同速度或方位的信号或噪声。弱信号初集信噪比的提高使震中位置的估计更加准确。相关方法将相关器输出表示为速度或方位角的函数，是识别地震震相的客观辅助方法。1 000公里处的实验阵列记录的Gnome核事件的速度滤波记录使至少能够识别出10个地震震相，其中许多是来自莫霍洛维奇不连续面的多次反射。反射波的传播时间可以推算出传播路径上地壳的平均厚度。举例说明了阵列技术在远震事件中的应用，包括探测和识别岩心震相，以及减少记录站附近信号产生的噪声。给出了几种阵型的理论响应，并讨论了它们的优缺点。给出了交叉阵的理论性能，包括相关方法的应用和对速度或方位角测量误差的讨论。推导了随机噪声情况下相关器信噪比的理论表达式。给出了实验阵列的详细信息，包括选址标准。还介绍了目前的模拟处理设施和正在建设中的专用计算机。
Arrays of seismometers, spaced over a distance comparable to the longest apparent wavelength of the signal, have been used to facilitate the separation and identification of seismic phases by a process ofvelocity filtering. Individual seismometers in the array are recorded on separate tracks of magnetic tape, and summed on playback with the insertion of time delays to cancel the propagation delays of the required signal. The inserted delays have the effect oftuningthe array to a required velocity and azimuth, thereby discriminating against signals or noise of different velocity or azimuth. The improvement in signal/noise ratio of weak signal onsets enables a more accurate estimate to be made of epicentre location. Correlation methods, presenting the correlator output as a function of velocity or azimuth, are an objective aid to identifying seismic phases. Velocity filtered records of the Gnome nuclear event, recorded by an experimental array at a distance of 1000 km, enabled at least ten seismic phases to be identified, many of them being multiple reflexions from the Mohorovicic discontinuity. The travel times of the reflexions enabled the mean thickness of the crust along the propagation path to be deduced. Examples are given to show the application of array techniques to teleseismic events, including the detection and identification of core phases, and reduction of noise generated by the signal in the vicinity of the recording station. The theoretical responses of arrays of several configurations are presented, and their relative merits discussed. The theoretical performance of cross arrays is given in detail, including the application of correlation methods and a discussion of errors in velocity or azimuth determination. Theoretical expressions are derived for correlator signal/noise ratios in the case of random noise. Details are given of the experimental arrays, including siting criteria. The present analogue processing facility, and a special purpose computer under construction, are also described.