用双差定位结果分析华北地区的地震活动
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摘要
华北地区北部是阴山—燕山隆起区、华北平原和太行山隆起的交界处,区域内地震活跃,北部有张家口—渤海地震活动带(张渤带),西邻山西地震活动带。本研究采用双差定位法对华北地区2006—2009年发生的地震进行重新定位,结果显示,近年来华北地区的地震主要集中在北部的张渤带上,总体呈WNW向分布。震源深度主要集中在0～20km的中上地壳,占地震总数的96.3%,有大约57.5%的地震分布在10km以上的地壳内。张渤带东部的唐山地区是该地震带上地震最密集的地区,地震分布与区域内的断层有密切关系。华北平原中南部的邢台地区也是地震相对较密集的区域,定位结果显示,邢台地区的新河断裂可能深达Moho面,在该断裂的下方可能存在速度异常体,把邢台地区西南部的地震活动从空间上隔离成上下两部分。沿新河断裂的地震分布出现异常,在深度10km处,地震分布由北东向西南逐渐与上部的地震分离,震源深度逐渐加深,最深可达30km左右。
North of Huabei region is the junction of three tectonic elements which are Huabei subsidence,Yanshan uplift,and Taihang uplift.This region is strongly active.Zhangjiakou-bohai seismic belt is in the north of this region,and Shanxi seismic belt is in the west.Using double difference algorithm,earthquakes occurred from 2006 to 2009 are relocated.The results of relocation show that many earthquakes distribute in the Zhangjiakou-bohai seismic belt,and the direction is WNW.The depth of the earthquakes distribution is from 0 to 20 km with a proportion of 96.3%.And the depths of 57.5% earthquakes are above 10 km in the upper crust.Thangshan region is active,and the distribution of the earthquakes is closely related to seismic faults.In the middle of Huabei subsidence,Xingtai region is also active.In this region,the depth of Xinhe fault can reach to Moho.There is abnormal velocity region,in which the distribution of earthquakes is separated into two parts.The distribution of earthquakes is tilted from northeast to southwest,and the focal depth becomes deep gradually.
North of Huabei region is the junction of three tectonic elements which are Huabei subsidence,Yanshan uplift,and Taihang uplift.This region is strongly active.Zhangjiakou-bohai seismic belt is in the north of this region,and Shanxi seismic belt is in the west.Using double difference algorithm,earthquakes occurred from 2006 to 2009 are relocated.The results of relocation show that many earthquakes distribute in the Zhangjiakou-bohai seismic belt,and the direction is WNW.The depth of the earthquakes distribution is from 0 to 20 km with a proportion of 96.3%.And the depths of 57.5% earthquakes are above 10 km in the upper crust.Thangshan region is active,and the distribution of the earthquakes is closely related to seismic faults.In the middle of Huabei subsidence,Xingtai region is also active.In this region,the depth of Xinhe fault can reach to Moho.There is abnormal velocity region,in which the distribution of earthquakes is separated into two parts.The distribution of earthquakes is tilted from northeast to southwest,and the focal depth becomes deep gradually.
引文
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[2]李乐,陈棋福,陈顒.首都圈地震活动构造成因的小震精定位分析[J].地球物理学进展,2007,22(1):24-34.
[3]万永革,沈正康,刁桂苓,等.利用小震分布和区域应力场确定大震断层面参数及其在唐山地震序列中的应用[J].地球物理学报,2008,51(3):793-804.
[4]Waldhauser F.Ellsworth L W.A Double-Difference Earthquake Location Algorithm:Method andApplication to the Northern Hayward Fault[J].California Bulletin of the Seismological Society of A-merica,2000,6(90):1 353-1 368.
[5]徐杰,宋长青,楚全芝.张家口—蓬莱断裂带地震构造特性的初步探讨[J].地震地质,1998,20(2):146-154.
[6]Geiger L.Probability method for determination of earthquake epicenters from arrival time only[J].1921,Bull St Louis Univ,60-71.
[7]杨智娴,陈运泰.用双差地震定位法再次精确测定1998年张北—尚义地震序列的震源参数[J].地震学报,2004,16(2):115-120.
[8]于湘伟,张怀,陈运泰.华北地区地震重新定位结果分析[J].大地测量与地球动力学,2010,30(2):29-33.
[9]Zhao Bo,Shi Yutao,Gao Yuan.Relocation of aftershocks of the Wenchuan MS8.0earthquake andits implication to seismotectonics[J].Earthquake Science,2011,24(1):107-113.
[10]朱艾斓,徐锡伟,胡平,等.首都圈地区b值随震源深度的变化:对地震成核的意义[J].科学通报,2005b,50(9):1-5.
[11]朱艾斓,徐锡伟,刁桂苓,等.汶川MS8.0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):759-767.
[12]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研究[J].中国科学D辑:地球科学,2008,38(10):1-8.
[13]祝治平,张建狮,张先康,等.张北—尚义地震区的壳幔构造[J].中国地震,1999,15(1):65-73.
[14]王夫运,张先康,陈颙,等.张渤构造带中东段二维P波速度结构[J].地震学报,2004,26(增刊):31-41.
[15]王峻.首都圈地壳上地幔三维S波速度结构的接收函数研究[D].2007硕士论文.
[16]李志才,许才军,赵少荣,等.基于地壳分层的唐山地震断层震后变形分析[J].地球物理学进展,2005,20(4):961-968.
[17]张四昌,刁桂苓.唐山地震序列的构造过程[J].中国地震,1992,8(2):73-80.
[18]邵学钟,张家茹,张思亚,等.邢台地震区深部构造背景的地震转换波探测和研究[J].地球物理学报,1993,36(5):609-620.
[19]张家茹,邵学钟,张思亚,等.邢台强震的深部三维构造背景和孕震条件[J].地震地质,1994,16(4):319-328.
[20]尹京苑,梅世蓉,薛艳.邢台地震区地壳速度结构特征与强震孕育发生的关系[J].地球物理学报,1999,42(5):629-639.
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