Apparent Weekly and Daily Earthquake Periodicities in the Western United States
Apparent Weekly and Daily Earthquake Periodicities in the Western United States
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DOI：
10.1785/0120080217
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发表时间：
2009-08-01
影响因子：
3
通讯作者：
Gao, Stephen S.
中科院分区：
文献类型：
--
作者：
Atef, Ali H.;Liu, Kelly H.;Gao, Stephen S.
利用美国西部>= 1级地震对视地震活动率（ASR）进行分析，证实存在周期为1天和7天的显著谱峰。1963-2008年期间，周日记录的地震次数比平日高5%左右，更显著的是，清晨的ASR比白天的ASR增加9%。周变化和日变化在空间分布上的显著相似性表明，这两种类型的变化具有相同的来源，并且都源于导致地震台网可探测性周期性变化的文化噪声的周期性变化。与高速公路交通流数据的比较表明，高速公路上的交通流并不是观察到的周期性的唯一重要因素。相反，来自所有地面交通、操作机械和建筑物震动的环境噪声可能是观测到的明显周期性的主要原因。观察到的ASR反映的环境噪声的时间变化可以作为选择对噪声敏感的科学实验的最佳时间/天的客观准则。
Analysis of apparent seismicity rate (ASR) using magnitude >= 1 earthquakes located in the western United States confirmed the existence of prominent spectral peaks with periods of 1 and 7 days. The number of recorded earthquakes on Sundays for the duration of 1963-2008 is about 5% higher than that on weekdays, and, more significantly, there is a 9% increase of ASR in the early morning compared with that in the middle of the days. Significant similarities in the spatial distributions of the weekly and daily variations suggest that the two types of variations have the same sources and both originate from periodic variations in cultural noise that lead to periodic variations in the detectability of the seismic networks. Comparisons with freeway traffic flow data suggest that traffic flow on the freeways is not the only significant factor in the observed periodicities. Instead, ambient noise from all the ground traffic, operating machineries, and building shaking is probably the major cause of the observed apparent periodicities. The observed temporal variations in ambient noise as reflected by the ASR can be used as objective guidelines for choosing the best time/day for noise-sensitive scientific experiments.