【摘要】 利用云南地区43个宽频带地震台站记录的2008～2010年垂直分量数据,计算了台站对间的互相关函数并得到了5～40 s周期的瑞利面波信号。研究发现在5～10 s周期范围内,瑞利面波信号之前存在很强的前驱信号,该信号能量优势频段为0.1～0.2 Hz,其到时接近噪声互相关函数零点,视速度约为30 km/s。该信号到时随季节存在正负交替变化,进一步的质点分析表明该信号为出射角较小的P波信号。参考已有的研究,认为远场地脉动噪声源中的P波信号穿过地球深部到达云南地区,形成了噪声互相关函数中视速度较高的体波信号,并且相关的噪声源位置在冬季和夏季分别位于北太平洋和南印度洋,具有明显的季节性空间变化。更多还原

【Abstract】 Using vertical component records observed at 43 broad-band seismic stations from 2008 to 2010 in Yunnan,we calculate the noise-cross correlation functions between each station-pair and obtain Raleigh surface wave in the period from 5s to 40s.We find that in the period from 5s to 10s,and before Rayleigh wave,there is a strong precursory wave whose dominant frequency band is between 0.1 Hz and 0.2 Hz and whose arrival time is near the zero of cross correlation functions.Moreover its negative arrival-time in Winter alternates with the positive ones in Summer.Through further analysis of particle-motion,we confirm that this wave is P-wave with smaller reflection angle whose apparent velocity is about 30km/s.Referring to the relevant research results,we conclude that originating from the ambient micro-tremor noise source at a teleseismic distance,P-wave travels through deep earth to Yunnan and reaches a higher apparent velocity.The ambient noise source,which locates in South Indian Ocean in Summer and North Pacific Ocean in Winter,varies seasonally and spatially.更多还原