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流动地震观测背景噪声的台基响应

DOI: 10.6038/cjg20130315, PP. 857-868

Keywords: 宽频带地震计,流动地震台站,噪声,功率谱密度,台基处理,对比观测

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Abstract:

大规模流动地震台阵技术发展为高分辨率深部结构成像提供了重要基础,背景噪声是影响流动地震观测质量的关键因素.为掌握流动地震观测噪声规律,发展流动地震观测降噪技术,编制流动地震观测技术规范,我们开展了针对不同台基流动地震观测背景噪声的观测实验与分析.其中,山西省临汾市五个地点架设了共22个对比观测台站,进行了超过一年半的连续观测.通过计算不同频段范围内背景噪声记录的加速度功率谱密度,研究了不同场地条件和环境噪声下流动地震观测台站的噪声特征及其台基响应,分析了不同台基处理方式对噪声的抑制效果.结果表明:(1)高频人为噪声和长周期自然噪声是影响流动地震观测质量的主要噪声,可以通过增加台基深度和改善台基处理方式等方法降低其影响;(2)增加台基深度能有效地降低长周期噪声和高频噪声,2m深坑能使高人为噪声台站各分量的高频频段和长周期频段分别降低5dB和10dB;(3)由于其不稳定性,沙子台基的水平分量在长周期频段一般要高于摆墩台基5dB,流动地震观测中推荐使用摆墩台基;(4)台站位置、台站内部温度和空气流动都是影响台站噪声的重要因素.在此基础上提出了不同场地条件和噪声环境下的台基处理建议和适合国情的移动地震台阵台站建设参考方案,有助于流动地震观测野外工作的标准化和规范化.

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