论文部分内容阅读
利用首都圈数字地震台网接收人工地震信号,进行地下结构研究具有重要意义.但人工震源释放的能量小,激发的地震波以短周期为主,因此本文较全面地研究了地震台网对短周期微弱信号(1～20 Hz)的检测能力:(1)分析了台网的背景噪声,结果表明基岩台址的地震台噪声比沉积盖层台址的地震台噪声低约13 dB,这相当于近1个震级的检测阈值;夜间的噪声比白天低约5 dB;噪声有逐年增高的趋势,2006年比2001年噪声提高约4 dB.(2)分析了在台网内进行的药量为25 kg的陆地井下爆破实验,一次爆破相当于0.69级(M_L)的天然地震,有18个地震台可辨认爆炸产生的 Pg、Pm 或 Pc 波;离爆破点218 km 的基岩台,仍可以接收到振幅只有1.6 nm 的 Pm 波.这个结果可为地震勘探实际工作提供参考.(3)研究了台网外核爆试验的信号特征,2006年发生在朝鲜的地下核试验是一次检验台网检测微弱信号能力的好机会.波形记录经1～5Hz 滤波后,台网中噪声小的18个基岩台可以清晰辨认核爆破产生的 P 波或 Lg 波,P 波平均振幅为16 nm,计算的平均震级为 m_b 4.3,和 NEIC 给出的震级相同;分析还表明背景噪声是影响台站信号检测能力的主要因素之一.
It is of great significance to study the underground structure by using the artificial seismic signal from the digital seismic network in the metropolitan area, but the energy released by the artificial source is small and the excited seismic waves are dominated by the short period. Therefore, Weak signal (1 ~ 20 Hz) detection ability: (1) Analyzing the background noise of the network, the results show that the seismic noise of the bedrock station is about 13 dB lower than the seismostat of the sedimentary cover station, which is quite The detection threshold of nearly 1 magnitude was lower; the nighttime noise was about 5 dB lower than that of daytime; the noise tended to increase year by year, and the noise was increased by about 4 dB in 2006 compared with 2001. (2) For a 25 kg downhole borehole blasting experiment, the first blast corresponds to a natural earthquake of 0.69 level (M_L) with 18 stations recognizing the Pg, Pm or Pc waves generated by the explosion; the bedrock station 218 km away from the blast site Can receive the Pm wave with an amplitude of only 1.6 nm.This result can provide reference for the practical work of seismic exploration. (3) Studied the signal characteristics of the nuclear explosion test outside the Taiwan network. The underground nuclear test that occurred in North Korea in 2006 was a testing platform Network detection weak signal ability is good After the waveform record is filtered by 1 ~ 5Hz, the 18 bedrock stations with small noise in the network can clearly identify the P wave or Lg wave generated by nuclear explosion, the average amplitude of P wave is 16 nm and the average magnitude is calculated as m_b 4.3 , And NEIC gives the same magnitude; the analysis also shows that background noise is one of the main factors that affect the station signal detection capability.