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龙门山断裂带二侧的地壳厚度和速度结构存在很大差异,所以过去采用的单一均匀速度模型定位方法并不合适。Hypo2000定位程序对震中所在的不同区域进行分区分层对应,得出非均匀速度模型。用Hypo2000定位程序对汶川8·0级地震前后十余年187个地震台网记录进行了整理、筛选,得出震中分布图显示震前龙门山断裂带北端,即北川以北没有太多地震,主要还是活跃在中南部映秀地带,汶川8·0级地震也发生在这个地区,震后沿龙门山断裂带往北,北川以北出现了较多的余震。从余震深度剖面图看出,龙门山余震带南段断裂带呈上陡下缓的铲形断裂形态,余震带北段具有近乎直立的陡倾破裂结构,且地表破裂的二侧均有余震分布。
The thickness and velocity structures of the crust on both sides of the Longmen Shan fault zone are quite different. Therefore, the single uniform velocity model location method adopted in the past is not suitable. Hypo2000 positioning program to subdivide and map the different regions where the epicenter is located to obtain a non-uniform velocity model. Using Hypo2000 locating program, 187 records of seismographs over the past ten years after Wenchuan Ms 8.0 earthquake were sorted out and screened. The epicenter distribution map shows that there is not much earthquakes in the north of Beimen fault zone before the earthquake, Mainly still active in the Yingxiu area of central and southern China, the 8.0 Wenchuan earthquake also occurred in this area. After the earthquake, there were more aftershocks northward along the Longmenshan fault belt and north of Beichuan. As seen from the aftershock profile, the southern fault zone of the Longmen Shan aftershock zone shows a steep-downdrapping, spatulate fracture pattern. The northern section of the aftershock zone has a nearly upright steep-dumping structure with aftershock distribution on both sides of the surface rupture .