西拉木伦断裂带东沿背景噪声特征分析

Characteristics of ambient noise along the east of Xar Moron fault zone

摘要:

利用中国地震局的“中国地震科学台阵——华北地区东部”(简称科学台阵3.2期)项目西拉木伦断裂带东沿地区26个流动台站连续观测数据,通过计算其加速度功率谱密度和相应的概率密度函数及1~20 Hz频段速度均方根值,研究西拉木伦断裂带东沿地区背景噪声特征。研究结果表明,高频段背景噪声时空分布差异性显著,噪声源主要来自人类活动;微震频段背景噪声主要来自海洋活动,其中高频微震频段背景噪声没有时空分布差异;低频微震频段背景噪声有一定的时空分布差异,白天差异性相比夜间更突出,这主要因温度变化和观测井微变形引起;低频段,白天三分向噪声水平大于夜间,且水平向噪声水平和动态范围大于垂直向,主要因白天环境温度变化和地倾斜影响大于夜间,且水平向对温度和地倾斜比垂直向更敏感导致。

Abstract:

This paper analyzed the characteristics of ambient noise on the east side of Xar Moron fault zone according to three key values: root mean square (RMS) of velocity at 1-20 Hz, power spectral density (PSD) of acceleration, and corresponding probability density function (PDF). The continuous data were recorded by 26 mobile seismic stations in the study area set up under the project "ChinArray-eastern North China". The results indicate that the temporal and spatial distributions of ambient noise in the study area show various characteristics at three different frequency bands: (1) The temporal and spatial distribution of ambient noise in the high frequency band is significantly different, and the noise source mainly comes from human activities. (2) The ambient noise in micro-seismic frequency band mainly comes from marine activities. The temporal and spatial distribution of ambient noise at high-frequency micro-seismic frequency band has no difference, while that at low-frequency micro-seismic frequency band has certain difference, which is due to the temperature change and micro deformation of observation wells; the difference is more prominent in the daytime than at night. (3) In the low frequency band, the three-component noise in the daytime is larger than that at night, and the level and dynamic range of noise in the horizontal direction are higher than that in the vertical direction, for the influence of ambient temperature change and ground tilt in the daytime is greater than that at night, and the horizontal direction is more sensitive to temperature and ground tilt than the vertical direction.