对汶川8·0级地震前后震源的重新定位
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摘要
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 crustal thickness and velocity structure in both sides of Longmenshan fault zone are very different,so in the past using a single uniform velocity model was not appropriate positioning method,Hypo2000 locator epicenter located in different regions of the partition layer corresponds to come to non-uniform velocity model.In this paper,Hypo2000 locator for 187 seismic Network records before and after Wenchuan 8.0 earthquake 10 years are sorted and filtered.Draw the epicenter distribution shows the earthquake was not too much in the north of Longmenshan fault zone including the north of Beichuan before earthquakes,mainly still active in Yingxiu south area,and 8.0 magnitude earthquake happened in this region.After the earthquake Longmen mountains to the north along the fault zone to the north of Beichuan appeared more aftershocks.From the depth profile of aftershocks Longmen mountains,it shows that southern aftershocks belts has the characteristics of fault zone steep slowly shovel form fracture form,but in the north of the aftershocks belt,it has almost vertical steep loose broken structure,and the surface of the broken in both sides are corresponded to the aftershocks distribution.
The crustal thickness and velocity structure in both sides of Longmenshan fault zone are very different,so in the past using a single uniform velocity model was not appropriate positioning method,Hypo2000 locator epicenter located in different regions of the partition layer corresponds to come to non-uniform velocity model.In this paper,Hypo2000 locator for 187 seismic Network records before and after Wenchuan 8.0 earthquake 10 years are sorted and filtered.Draw the epicenter distribution shows the earthquake was not too much in the north of Longmenshan fault zone including the north of Beichuan before earthquakes,mainly still active in Yingxiu south area,and 8.0 magnitude earthquake happened in this region.After the earthquake Longmen mountains to the north along the fault zone to the north of Beichuan appeared more aftershocks.From the depth profile of aftershocks Longmen mountains,it shows that southern aftershocks belts has the characteristics of fault zone steep slowly shovel form fracture form,but in the north of the aftershocks belt,it has almost vertical steep loose broken structure,and the surface of the broken in both sides are corresponded to the aftershocks distribution.
引文
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[2]朱介寿.汶川地震的岩石圈深部结构与动力学背景[J].成都理工大学学报:自然科学版,2008,35(4):350.
[3]傅莺,范军.Hypocenter和Hypo2000地震定位方法在攀枝花—会理地震序列中的应用[J].四川地震,2010:8.
[4]黄媛,吴建平,张天中,等.汶川8.0级大地震及其余震序列重定位[J].中国科学D辑:地球科学,2008,38(10):1242.
[5]吕坚,苏金蓉,斩玉科,等.汶川8.0级地震序列重新定位及其发震构造初探[J].地震地质,2008,30(4):917.
[6]王勤彩,陈章立,郑斯华.汶川大地震余震序列震源机制的空间分段特征[J].科学通报,2009,54(16):2350.
[7]朱艾斓,徐锡伟,刁桂苓,等.汶川8.0地震部分余震重新定位及地震构造初步分析[J].地震地质,2008,30(3):763.
[8]贾东,陈竹新,贾承造,等.龙门山褶皱冲断带构造解析与川西前陆盆地的发育[J].高校地质学报,2003,9(3):463.
[9]徐朝繁,潘纪顺,王夫运,等.龙门山及其邻近地区深部地球物理探测[J].大地测量与地球动力学,2008,28(6):32.
[10]徐锡伟,闻学泽,叶建青,等.汶川Ms8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):598.
[11]朱艾斓,徐锡伟,周永胜,等.川西地区小震重新定位及其活动构造意义[J].地球物理学报,2005,48(3):629.
[12]张国民,邵志刚,刘桂萍,等.汶川8.0级地震构造动力成因分析[J].地震,2009,29(1):164.
[13]蒋国芳.利用地震转换求取四川地壳厚度的初步尝试[J].四川地震,1987(3):36.
[14]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学:D辑地球科学,2008,38(10):1187.
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