广东地震预警网三类站环境地噪声水平评估OACSTPCD

Ambient ground noise calculations were performed for 71 reference stations,201 strong motion stations,and 900 intensity stations of Guangdong Earthquake Early Warning(EEW)Network.The overall assessment was favorable,meeting national observational standards.Specifically,noise levels from the seismic channels of the reference stations fell between NHNM and NLNM,significantly lower than the M1.5 amplitude spectrum models,with RMS values primarily in the order of magnitudes of 10-9-10-8 m/s.In addition,65 reference stations at level I were assessed as high-quality stations.The noise levels from strong seismic channels of the reference stations was generally lower than the M1.5,approaching NHNM,with RMS values primarily in the order of magnitudes of 10-7-10-6 m/s2.The noise levels of strong motion stations were generally lower than the M2.5,with RMS values primarily in the order of magnitudes of 10-6-10-5 m/s2.The noise levels of intensity stations were lower than the M3.5,with RMS values mainly in the order of magnitude of 10-4 m/s2.In most intensity stations,strong seismic channels of some reference stations,and a few strong motion stations,the ambient noise mainly reflects the inherent self-noise of intensity meters or accelerometers,which was meaningless for cross-correlation analysis of background noise.Additionally,the vertical component noise of intensity stations was significantly louder than the horizontal component noise(by approximately 0.5 times)due to the performance of intensity meters.