Seismic velocity changes caused by the Earth tide: Ambient noise correlation analyses of small‐array data
Seismic velocity changes caused by the Earth tide: Ambient noise correlation analyses of small‐array data
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地球潮引起的地震速度变化：小阵数据的环境噪声相关分析
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
Sachiko Tanaka
中科院分区：
文献类型：
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作者：
Tomoya Takano;T. Nishimura;H. Nakahara;Y. Ohta;Sachiko Tanaka
我们通过对日本东北部由7台地震仪组成的小型阵列记录的环境地震噪声进行相互关联函数（CCF）分析，研究了由于地球潮汐引起的地震速度变化。我们计算了从理论潮汐体积应变预测的膨胀和收缩事件的ccf。两期的CCFs高度相关，但其阶段差异很小。在1-2 Hz时，地震速度变化为- 0.19±0.06%，解释了相位差，这是由于潮汐应变引起浅层地下裂缝或孔隙的打开/关闭造成的。地震速度变化的应变敏感性估计为6.9 × 104应变−1，这与以往人工震源研究的结果基本一致。
We examine seismic velocity changes due to the Earth tide by conducting cross‐correlation function (CCF) analyses of ambient seismic noise recorded at a small array composed of seven seismometers in northeastern Japan. We calculate CCFs for the dilatational and contractional episodes that are predicted from theoretical tidal volumetric strains. CCFs of the two episodes are highly correlated, but tiny differences are found in their phases. The phase differences are explained by seismic velocity changes of −0.19 ± 0.06% at 1–2 Hz, which are interpreted to be caused by opening/closure of cracks or pores in the shallow subsurface due to the tidal strain. Strain sensitivities of the seismic velocity changes are estimated to be 6.9 × 104 strain−1, which are almost consistent with those reported in previous studies using artificial sources.