汶川8.0级地震序列联合定位研究
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摘要
使用联合定位方法对2008年5月12日至7月7日ML≥3.0的1 028次地震进行重新定位。针对EVT格式的波形数据,重新求取视出射角参数和到时参数,建立地震波到时与视出射角联合定位方法。视出射角参数对深度较敏感,其联合定位结果能保证经度和纬度方向上的定位精度,特别是能提高对深度的分辨能力。联合定位结果表明,地震序列平均震源深度为12.8 km,深度分布在4~20 km(上地壳),其优势分布在8~18 km,最终汇集到埋深约20 km滑脱面(带)上。地震深度分布显示断层具有分段性,南段以逆冲为主,北段以走滑为主。地震集中位于断层的断坡部位,其断坡部位是应力易于积累的区域(深度约为8~18 km),是主震的发震位置。
In this paper 1028 aftershocks from May.12 to Jul.7,2008 have been relocated precisely using Multiparameter Seismic Joint Location method.The parameters of apparent emergence angles and arrival time are extracted according to the wave data with EVT format.The objective function in the method of Multiparameter Seismic Location with apparent emergence angles and arrival time was founded.The apparent emergence angle has the very strong sensitivity to depth.The results of Multiparameter Seismic Location are able to guarantee the accuracy in the directions of latitude and longitude,especially to enhance the depth resolution effectively.The average depth of the earthquake sequence is about 12.8 km,distributing in a range from 4 to 20 km(up crust),and the superiority distribution is from 8 to 18 km,coming together on the detachment plane(belt) with a depth of 20 km approximately.The depth distributing shows segmented fault.The southern and northern segments are thrust and strike-slip respectively.The aftershocks located intensively at the fault ramp,which is the region of stress accumulation(with depth about 8 to 18 km) and the main shock occurred at this location.
In this paper 1028 aftershocks from May.12 to Jul.7,2008 have been relocated precisely using Multiparameter Seismic Joint Location method.The parameters of apparent emergence angles and arrival time are extracted according to the wave data with EVT format.The objective function in the method of Multiparameter Seismic Location with apparent emergence angles and arrival time was founded.The apparent emergence angle has the very strong sensitivity to depth.The results of Multiparameter Seismic Location are able to guarantee the accuracy in the directions of latitude and longitude,especially to enhance the depth resolution effectively.The average depth of the earthquake sequence is about 12.8 km,distributing in a range from 4 to 20 km(up crust),and the superiority distribution is from 8 to 18 km,coming together on the detachment plane(belt) with a depth of 20 km approximately.The depth distributing shows segmented fault.The southern and northern segments are thrust and strike-slip respectively.The aftershocks located intensively at the fault ramp,which is the region of stress accumulation(with depth about 8 to 18 km) and the main shock occurred at this location.
引文
[1]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),2008,38(10):1 242-1 249.
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[4]陈九辉,刘启元,李顺成,等.汶川MS8.0地震余震序列重新定位及其地震构造研究[J].地球物理学报,2009,52(2):390-397.
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[11]徐锡伟,闻学泽,郑荣章,等.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(D辑),2003,33(增刊):151-162.
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[13]徐锡伟.5.12汶川8.0级地震地表破裂图集[M].北京:地震出版社,2009.
[14]聂晓红,李莹甄.2008年8月30日和静MS5.6地震序列及震前部分测震学异常分析[J].内陆地震,2010,24(2):116-123.
[15]唐明帅,王海涛,段天山.利用和田地震台阵数据对2008年于田7.3级地震序列重新定位[J].内陆地震,2010,24(3):227-235.
[16]杨成荣,唐明帅.新疆于田7.3级地震及部分强余震震源参数的重新测定[J].内陆地震,2010,24(1):18-24.
[2]吕坚,苏金蓉,靳玉科,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):67-74.
[3]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):98-105.
[4]陈九辉,刘启元,李顺成,等.汶川MS8.0地震余震序列重新定位及其地震构造研究[J].地球物理学报,2009,52(2):390-397.
[5]李稳,张元生,何斌.地震波到时与视出射角联合定位方法研究[J].西北地震学报,2009,31(3):34-39.
[6]李稳.地震波到时与视出射角联合定位方法研究[D].兰州:中国地震局兰州地震研究所,2008.
[7]何斌,张元生,李稳.计算地震初至波视出射角方法[J].西北地震学报,2010,32(1):11-15.
[8]刘启元,陈九辉,李顺成,等.汶川MS8.0地震:川西流动地震台阵观测数据的初步分析[J].地震地质,2008,30(3):584-596.
[9]陈九辉,刘启元,李顺成,等.川西地区地壳厚度和泊松比结构研究[J].中国地球物理,2008.
[10]陈运泰.汶川特大地震的震级和断层长度[J].科技导报,2008,26(10):26-27.
[11]徐锡伟,闻学泽,郑荣章,等.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(D辑),2003,33(增刊):151-162.
[12]徐锡伟,张培震,闻学泽,等.川西及其邻近地区活动构造基本特征与强震复发模型[J].地震地质,2005,27(3):446-461.
[13]徐锡伟.5.12汶川8.0级地震地表破裂图集[M].北京:地震出版社,2009.
[14]聂晓红,李莹甄.2008年8月30日和静MS5.6地震序列及震前部分测震学异常分析[J].内陆地震,2010,24(2):116-123.
[15]唐明帅,王海涛,段天山.利用和田地震台阵数据对2008年于田7.3级地震序列重新定位[J].内陆地震,2010,24(3):227-235.
[16]杨成荣,唐明帅.新疆于田7.3级地震及部分强余震震源参数的重新测定[J].内陆地震,2010,24(1):18-24.
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