DETERMINATION OF EARTHQUAKE SOURCE PARAMETERS FROM WAVEFORM DATA FOR STUDIES OF GLOBAL AND REGIONAL SEISMICITY
DETERMINATION OF EARTHQUAKE SOURCE PARAMETERS FROM WAVEFORM DATA FOR STUDIES OF GLOBAL AND REGIONAL SEISMICITY
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DOI：
10.1029/jb086ib04p02825
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发表时间：
1981-01-01
影响因子：
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通讯作者：
WOODHOUSE, JH
中科院分区：
文献类型：
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作者：
DZIEWONSKI, AM;CHOU, TA;WOODHOUSE, JH
利用波形资料不仅可以导出地震的震源机制，而且可以确定给定频率下“最佳点源”（应力剩余密度的质心）的震源坐标。因此，地震学的两个经典问题被合并成一个单一的过程。给定一个估计的起源时间，震中坐标和深度，一个初始的力矩张量推导使用的方法详细描述的吉尔伯特和Dziewonski（1975）的变化之一。这组参数表示迭代过程的起始值，在该迭代过程中，发现矩张量的元素的扰动与震源参数的变化同时发生。总的来说，该方法稳定，收敛速度快.虽然这种方法是一种通用的方法，但我们在分析SRO和ASRO数字网络仪器记录的长周期体波数据的背景下提出了这种方法。似乎可以使用这种特殊方法处理的地震震级上限在7.5和8.0之间;此时下限约为5.5，但可以通过扩大分析的通带来扩展，以包括周期短于45 s的能量。由于每年有数百次震级超过5.5级的地震，现在不仅可以详细研究重大事件的震源机制，还可以研究余震系列等。我们研究了1977年8月19日松巴地震的前震和几次余震，结果表明主震断层区应力状态的时间变化。49天后，距震中西北约150公里的一个地区成为地震活跃区。这些事件的走滑机制的意义与爪哇海沟北部板块的压缩应力松弛一致。我们分析的另一个有趣的结果是，对于11个中深度和大深度地震中的5个，矩张量的中间主值是显著的，而对于其余6个，它基本上是零，这意味着它们的机制与简单的双力偶表示一致。这两组地震之间有明显的区别。
It is possible to use the waveform data not only to derive the source mechanism of an earthquake but also to establish the hypocentral coordinates of the ‘best point source’ (the centroid of the stress glut density) at a given frequency. Thus two classical problems of seismology are combined into a single procedure. Given an estimate of the origin time, epicentral coordinates and depth, an initial moment tensor is derived using one of the variations of the method described in detail by Gilbert and Dziewonski (1975). This set of parameters represents the starting values for an iterative procedure in which perturbations to the elements of the moment tensor are found simultaneously with changes in the hypocentral parameters. In general, the method is stable, and convergence rapid. Although the approach is a general one, we present it here in the context of the analysis of long‐period body wave data recorded by the instruments of the SRO and ASRO digital network. It appears that the upper magnitude limit of earthquakes that can be processed using this particular approach is between 7.5 and 8.0; the lower limit is, at this time, approximately 5.5, but it could be extended by broadening the passband of the analysis to include energy with periods shorter that 45 s. As there are hundreds of earthquakes each year with magnitudes exceeding 5.5, the seismic source mechanism can now be studied in detail not only for major events but also, for example, for aftershock series. We have investigated the foreshock and several aftershocks of the Sumba earthquake of August 19, 1977; the results show temporal variation of the stress regime in the fault area of the main shock. An area some 150 km to the northwest of the epicenter of the main event became seismically active 49 days later. The sense of the strike‐slip mechanism of these events is consistent with the relaxation of the compressive stress in the plate north of the Java trench. Another geophysically interesting result of our analysis is that for 5 out of 11 earthquakes of intermediate and great depth the intermediate principal value of the moment tensor is significant, while for the remaining 6 it is essentially zero, which means that their mechanisms are consistent with a simple double‐couple representation. There is clear distinction between these two groups of earthquakes.