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首页> 外文期刊>Pure and Applied Geophysics >Observed Evolution of Linear and Nonlinear Effects at the Dahan Downhole Array, Taiwan: Analysis of the September 21, 1999 M 7.3 Chi-Chi Earthquake Sequence
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Observed Evolution of Linear and Nonlinear Effects at the Dahan Downhole Array, Taiwan: Analysis of the September 21, 1999 M 7.3 Chi-Chi Earthquake Sequence

机译：台湾大韩井下阵列观测到的线性和非线性影响的演变：对1999年9月21日M 7.3集集地震序列的分析

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— In this paper, the site characteristics of the Dahan downhole array are studied by analyzing the September 21, 1999 M 7.3 Chi-Chi earthquake sequence including the main shock and some aftershocks. The four-level array (0 m, 50 m, 100 m and 200 m) is located to the north of Hualien City in eastern Taiwan. Polarization analysis is used to check the orientation errors of the seismometers at different levels of depth. If the surface instrument is chosen as reference, the angle between the major polarization axes of the surface and any downhole records is the orientation error that must be corrected for the downhole accelerographs. The orientation errors at depths of 50 m, 100 m and 200 m are 32°, 120° and −84°. After the corrections, the coherency between the surface and downhole records is substantially improved. Spectral ratio analysis shows that the predominant frequency of the Chi-Chi main shock shifts to a lower frequency. We also simulate ground motions at different depths by using the Haskell method with a linear velocity structure model. The record at surface is chosen as the input motion. Compared with the observed data, ground acceleration can be well reproduced for the aftershocks (weak-motion events) of the September 21, 1999 M 7.3 Chi-Chi earthquake. However, for the Chi-Chi main shock, the synthetic waveform cannot match well with the observation neither in amplitude nor in phase. This indicates that large ground shaking probably induced the nonlinear site effect at that time, and the model used cannot support it.
机译：—本文通过分析1999年9月21日M 7.3集集（Chi-Chi）地震序列（包括主震和余震）来研究大韩井下阵列的场地特征。四层阵列（0 m，50 m，100 m和200 m）位于台湾东部花莲市的北部。极化分析用于检查地震仪在不同深度处的定向误差。如果选择地面仪器作为参考，则地面的主极化轴与任何井下记录之间的夹角就是定向误差，必须对井下加速度计进行校正。深度为50 m，100 m和200 m时的定向误差为32°，120°和-84°。校正之后，地表和井下记录之间的连贯性得到了显着改善。频谱比分析表明，Chi-Chi主冲击的主要频率移至较低频率。我们还使用Haskell方法和线速度结构模型来模拟不同深度的地面运动。选择表面上的记录作为输入运动。与观察到的数据相比，可以很好地再现1999年9月21日发生的Chi-Chi M 7.3地震余震（弱运动事件）的地面加速度。但是，对于Chi-Chi主震，合成波形无论在幅度还是相位上都无法与观测值很好地匹配。这表明当时大的地面震动可能引起了非线性场效应，并且所使用的模型无法支持该效应。

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