谢江涛,林丽萍,赵敏,谌亮. 2021. 四川地区地震背景噪声特征分析. 地震学报,43(5):533−550. doi: 10.11939/jass.20200148
引用本文: 谢江涛,林丽萍,赵敏,谌亮. 2021. 四川地区地震背景噪声特征分析. 地震学报,43(5):533−550. doi: 10.11939/jass.20200148
Xie J T,Lin L P,Zhao M,Chen L. 2021. Characteristics of seismic ambient noise in Sichuan region. Acta Seismologica Sinica43(5):533−550. doi: 10.11939/jass.20200148
Citation: Xie J T,Lin L P,Zhao M,Chen L. 2021. Characteristics of seismic ambient noise in Sichuan region. Acta Seismologica Sinica43(5):533−550. doi: 10.11939/jass.20200148

四川地区地震背景噪声特征分析

Characteristics of seismic ambient noise in Sichuan region

  • 摘要: 选取四川省数字测震台网2015年1月1日至2018年12月31日期间60个固定台站的三分量连续波形记录,计算了台站噪声加速度功率谱密度及相应的概率密度函数分布,统计了不同频率下的噪声功率谱密度值分布,对不同区域、不同频率下背景噪声水平的变化特征予以分析。结果表明:大部分地震台站的高频段噪声由于受到台站附近人为的、规律的作息生活和生产方式的影响,呈现明显的季节性变化和日变化,即夏季噪声水平升高,冬季降低,在农历春节期间达到全年最低值,地理空间分布特征不明显;第二类地脉动冬季噪声水平升高,夏季降低,季节性变化明显,平均变化为1—5 dB,且冬季峰值出现的频率向长周期方向移动1—2 s,呈现明显的地理空间分布特征,川东地区平均噪声水平最高,攀西地区次之,川西高原最低;与第二类地脉动相比,第一类地脉动观测到的噪声能量较弱,季节性变化不明显,地理空间分布的噪声水平差异明显减小;在20 s以上的长周期部分,台站噪声未呈明显的季节性和地理空间分布差异。此外,将地震计安置在山洞和井下,可以有效地降低台站周围干扰源、温度和压强对高频段和长周期观测的影响,噪声水平低于地表安装方式。

     

    Abstract: Based on the three-component continuous waveform data recorded by sixty permanent seismic stations in Sichuan seismic network from January 1, 2015 to December 31, 2018, this paper calculated the noise power spectral densities and corresponding probability density functions, then gave the statistical characteristics of noise power spectral density at different frequencies, and finally analyzed the characteristics of noise level at different regions and frequencies. The results show that the high-frequency seismic noises of most stations are affected by the nearby human activities, production mode and lifestyle, which has obvious seasonal and diurnal variations. The noise level increases during summer and decreases during winter with the lowest level during the Spring Festival in the whole year; and the geographical distribution is not obvious. For double-frequency microseisms, the noise level increases during winter and decreases during summer, and has obvious seasonal variation with an average of 1−5 dB, which has obvious geographical distribution characteristics. The average noise level in eastern Sichuan is the highest, followed by Panxi region, and the lowest in western Sichuan Plateau. The microseism peaks have different amplitudes and occur at different frequencies in summer and winter, with the peaks shifted by 1−2 s toward longer periods in the winter. Compared with the double-frequency microseism band, the noise energy at primary microseism band is weaker, the seasonal variation is not obvious, and the difference of noise level in geographical distribution is significantly reduced. While the long-period (>20 s) noise level has no obvious seasonal variation and no difference in geographical distribution. In addition, installing seismographs in caves and borehole can effectively reduce the influence of noise sources, temperature and pressure on high-frequency band and long-period observations, therefore the noise level is lower than that of shallow installations.

     

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