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依据由噪声信号提取面波格林函数的原理,利用福建省地震台网25个宽频带台站2007年7月2日—8月29日的脉动观测资料,得到了瑞雷波群速度在福建地区的分布,并将该结果作为下一步相对变化动态成像的背景速度分布.分布结果表明,福建地区周期为3—5s的瑞雷波群速度大致在2.9—3.1km/s之间,平均速度为3.0km/s,瑞雷波群速度分布呈北高南低的现象,这与福建地区北部多山、南部多平原盆地的地理环境有很好的吻合.而且,该群速度分布图在漳州盆地地区表现出一个非常明显的低速,这主要是因为受到盆地沉积层的影响.通过滑动窗(窗长为20d,步长1d)技术得到了观测区内周期约为3—5s的瑞雷波波速分布变化的连续图像;再利用扣除背景影响的技术,得到了2007年8月14日—2008年7月1日福建地区瑞雷波波速的相对变化时空动态图像.通过分析相对变化时空动态图像与该时间范围内发生的地震的对应关系,表明福建地区瑞雷波波速在多次网内中等强度的地震或震群(ML>3.0)中均表现出震前波速升高,震后下降恢复的变化趋势.初步分析认为,这可能与震前整个地区受到的应力增大震后应力得到释放所导致的介质变化有关.
Based on the principle of surface wave Greenland function extracted from noise signal and using the pulsation observation data from 25 broadband stations of Fujian Seismological Station from July 2 to August 29, 2007, the velocity of Rayleigh waves in Fujian region And the result is taken as the background velocity distribution of dynamic imaging for relative change in the next step.The distribution results show that the Rayleigh wave swarm with 3-5s periodicity in Fujian is roughly 2.9-3.1km / s, and the average velocity is 3.0km / s, the velocity distribution of the Rayleigh wave group is high in the north and low in the south, which is in good agreement with the geo-environment of the mountainous and southern multi-plains basins in the northern part of Fujian Province.Furthermore, The region shows a very obvious low velocity mainly due to the influence of the sedimentary layer in the basin.The Rayleigh wave velocity in the observation area is about 3-5s through the sliding window (window length of 20d, step size 1d) Then, using the technique of background subtraction, the space-time dynamic images of the relative change of the Rayleigh wave velocity in Fujian from August 14, 2007 to July 1, 2008 were obtained.Through the analysis of relative changes of spatio- The time range The results show that the Rayleigh wave velocity in Fujian area shows a trend of increasing velocity before the earthquake and decreasing and recovering after the earthquake in the moderate-intensity earthquakes or swarms (ML> 3.0) in multiple networks. Preliminary analysis suggests that this may be related to the change of medium caused by the release of stress after the earthquake, which is caused by the increase of stress in the whole area before the earthquake.