1982年卢龙M_S6.1地震余震序列震源机制的矩张量反演
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摘要
用矩张量反演的方法,通过对1982年10月19日河北卢龙MS6.1地震的余震序列的震源机制求解,认为卢龙盆地的主压应力轴方位角为N74°E,近东西向;而盆地的北边变为N43°E;在盆地中心有些部位主压应力轴转为北西方向,与盆地周边的主压应力轴方位几乎垂直.这说明在卢龙地震中构造的不同部位地壳应力方位很不一致,反映出卢龙地区构造活动的复杂性.一方面,由于卢龙位处中国大陆东部,受到来自东部的日本海盆地在太平洋板块驱动力作用下的挤压;另一方面,卢龙又夹持在燕山地块与华北板块之间,因而受块体边界的限制也是很明显的.
Using the moment tensor inversion method, we calculate the focal mechanisms for the aftershock sequence of the M_S6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the principal compressive stress axis in Lulong basin is nearly in the east-west direction with an azimuth of N74°E. However, in the north of the basin the stress axis changes to N43°E; and in some places near the center of the basin it changes to the northwest that is almost perpendicular to the P axis obtained by us from those events around the basin. This feature illuminates that in Lulong earthquake sequence, the stress direction is different in different parts of crustal structure, which shows that the tectonic movement in Lulong region is complex. This is because that Lulong is located in the eastern part of Chinese mainland and is subject to the compression of Japanese Sea Basin driven by the Pacific Plate. On the other hand, nipped by the Yanshan and North China blocks, Lulong is obviously restricted by the block boundaries.
Using the moment tensor inversion method, we calculate the focal mechanisms for the aftershock sequence of the M_S6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the principal compressive stress axis in Lulong basin is nearly in the east-west direction with an azimuth of N74°E. However, in the north of the basin the stress axis changes to N43°E; and in some places near the center of the basin it changes to the northwest that is almost perpendicular to the P axis obtained by us from those events around the basin. This feature illuminates that in Lulong earthquake sequence, the stress direction is different in different parts of crustal structure, which shows that the tectonic movement in Lulong region is complex. This is because that Lulong is located in the eastern part of Chinese mainland and is subject to the compression of Japanese Sea Basin driven by the Pacific Plate. On the other hand, nipped by the Yanshan and North China blocks, Lulong is obviously restricted by the block boundaries.
引文
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李文军,王培德,李春来,等.2005.近场精确定位在卢龙ML6.2地震发震构造研究中的应用[J].地震学报,27(4):377~384
王培德.1987.近震源强地面运动研究[D]:[学位论文].北京:国家地震局地球物理研究所,21~22
张四昌,刁桂苓.1992.唐山地震序列的构造过程[J].中国地震,8(2):73~80
张培震,邓起东,张国民,等.2003.中国大陆的强震活动与活动块体[J].中国科学,D缉,33(增刊):12~20
周云好.2002.2000年6月4日印度尼西亚苏门答腊南部MS8.0地震的时空破裂过程[J].中国地震,18(3):221~229
KennettBLN.1980.Seismicwavesinastratifiedhalfspace—Ⅱ.Theoreticalseismograms[J].GeophysJRastrSoc,61:1~10
KennettBLN,KerryNJ.1979.Seismicwavesinastratifiedhalfspace[J].GeophysJRastrSoc,57:557~583
MadariagaR.1983.EarthquakeSourceTheory:AReviewinEarthquakes,Observation,TheoryandInterpretation[M].Amsterdam,NewYork,Oxford:North-Holland,1~44
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