海原断裂在地壳深处的几何形态及其动力学意义
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摘要
用速度和界面联合反演方法对海原深地震反射资料进行了重新处理 .通过折波以及断层面反射波的走时反演 ,确定了深度为 1 0km以内海原断裂几何形态及断层内和围岩的速度结构 .观测资料表明 ,桩号从 3 7～ 3 9km这两千米的范围内 ,观测地震图的振幅大大衰减 ,表明断层在地下有相当的宽度 .结果表明 ,在海原断裂以北 ,基底面由西南向东北隆起 ,形成一个平缓的大单斜 ,在西安州附近中生代褶皱基底深约 3km ,向东北方向逐渐变浅 .在海原断裂以南 ,在西华山和南华山之间的盆地内 ,褶皱基底深约 2km ,向西南方向逐渐变浅 .断层在深度为 3km以内的倾角约 70° ;在深度为 3～ 1 0km范围内的倾角约 60°.从本文结果及其它多方面的引证 ,我们认为海原断裂从地表到地壳 1 0km深处均处于陡立状态 .
The deep seismic reflection data on profile HY2 are reprocessed by the method of simultaneous inversion of velocity distribution and interface position. By the travel-time inversion with the data of the diving wave Pg and fault plane reflection wave, we determine the geometric form and velocity of Haiyuan fault zone interior and surrounding rock down to 10 km depth. The measured data show that the amplitudes have strong attenuation in the range of stake number 37～39 km, suggesting the fault zone has considerable width in the crustal interior. The results of this paper indicate that to the north of the fault zone the crystalline basement interface upheaves gradually from southwest to northeast and becomes shallow gradually towards northeast, and that to the south of the fault zone, within the basin between Xihua and Nanhua mountains, the folded basement becomes shallow gradually towards southwest. The obliquity of the fault zone is about 70° above the 3 km depth, about 60° in the range of the 3～10 km depths. From the results of this paper and other various citations, we believe that Haiyuan fault zone is in steep state from the Earth′s surface to the depth of 10 km.
The deep seismic reflection data on profile HY2 are reprocessed by the method of simultaneous inversion of velocity distribution and interface position. By the travel-time inversion with the data of the diving wave Pg and fault plane reflection wave, we determine the geometric form and velocity of Haiyuan fault zone interior and surrounding rock down to 10 km depth. The measured data show that the amplitudes have strong attenuation in the range of stake number 37～39 km, suggesting the fault zone has considerable width in the crustal interior. The results of this paper indicate that to the north of the fault zone the crystalline basement interface upheaves gradually from southwest to northeast and becomes shallow gradually towards northeast, and that to the south of the fault zone, within the basin between Xihua and Nanhua mountains, the folded basement becomes shallow gradually towards southwest. The obliquity of the fault zone is about 70° above the 3 km depth, about 60° in the range of the 3～10 km depths. From the results of this paper and other various citations, we believe that Haiyuan fault zone is in steep state from the Earth′s surface to the depth of 10 km.
引文
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李松林,吴宁远,宋占隆,等.1997a.速度分布和界面位置的联合反演[J].地震学报,19(4):383～392
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李松林,樊计昌,吴宁远.1995.利用地震层析成像技术确定横向非均匀介质中速度分布和界面位置(英文)[J].地震研究,18(4):430～444
汤锡元,郭忠铭,陈荷立,等.1992.陕甘宁盆地西缘逆冲推覆构造油气勘探[M].西安:西北大学出版社,1～97
StadtlanderR ,BrownL .1997.Turningwavesandcrustalreflectionprofiling[J].Geophysics,62(1):335～341
TapponnirP ,MolnarP .1977.ActivefaultinganCenozonictectonicsofChina[J].JGeophysRes,82:2905～2930
国家地震局《鄂尔多斯周缘活动断裂系》课题组.1988.鄂尔多斯周缘活动断裂系[M].北京:地震出版社,1～152
国家地震局地质研究所,国家地震局兰州地震研究所.1990.海原活动断裂带[M].北京:地震出版社,99～116
李松林,张先康,张成科,等.2002.玛沁—兰州—靖边地震测深剖面地壳速度结构的初布研究[J].地球物理学报,45(2):210～217
李清河,郭守年,吕德徽.1999.鄂尔多斯西缘与南缘深部结构与构造[M].北京:地震出版社,13～15,229
李松林,吴宁远,宋占隆,等.1997a.速度分布和界面位置的联合反演[J].地震学报,19(4):383～392
李松林,宋占隆,石金虎,等.1997b.利用地震折波资料反演界面位置和速度分布[J].地震研究,20(4):402～409
李松林,樊计昌,吴宁远.1995.利用地震层析成像技术确定横向非均匀介质中速度分布和界面位置(英文)[J].地震研究,18(4):430～444
汤锡元,郭忠铭,陈荷立,等.1992.陕甘宁盆地西缘逆冲推覆构造油气勘探[M].西安:西北大学出版社,1～97
StadtlanderR ,BrownL .1997.Turningwavesandcrustalreflectionprofiling[J].Geophysics,62(1):335～341
TapponnirP ,MolnarP .1977.ActivefaultinganCenozonictectonicsofChina[J].JGeophysRes,82:2905～2930
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