河西走廊中部地区三维速度结构研究
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摘要
利用天然地震记录资料,对河西走廊中部地区三维速度结构与震源参数进行了反演,获得了该区的三维速度图像。分层速度结果反映出研究区深部结构的一些重要信息。①浅部沉积层的速度为5.00~6.15km/s,垂直速度梯度接近0.15km/s;结晶基底埋深约7km,速度为6.15km/s。②上地壳深达18km,速度约为6.33km/s;民乐盆地速度略高于祁连山和龙首山,阿拉善地块存在明显的向河西走廊下插的现象。③中地壳底部深约30km,速度为6.58km/s;较显著的速度变化区正位于北祁连与河西走廊过渡带。④下地壳厚度显示祁连山偏厚,莫霍面埋深为54km;河西走廊稍薄,莫霍面深约为52km;阿拉善地块莫霍面深53.5~53.0km,介于祁连山与河西走廊之间。在34~42km深度存在明显的低速层,速度约为6.5km/s。研究认为,龙首山断裂带可能是逆冲性质的上地壳断层,昌马—俄博断裂可能是一条近直立的中地壳断层。
The 3-D velocity tomography image of central Hexi Corridor was obtained by the joint inversion of 3-D velocity structure and focal parameters based on the S-P data of micro-earthquakes recorded by the digital seismic network. The inversed layering velocity structure does reflect some important features of the deep structure in the study area: ① The velocity of shallow deposition is about 5.00~6.15 km/s and the vertical velocity gradient is close to 0.15 km/s; the depth of the crystalline basement is about 7 km, with the velocity being 6.15 km/s. ② The depth of the upper crust is some 18 km, with the velocity being 6.33 km/s; the velocity of Minle basin is slightly higher than that of the North Qilian Mountain and the Longshou Mountain. The Alxa block is obviously thrusting under the Hexi Corridor. ③ The bottom of the middle crust is about 30 km in depth with the velocity being 6.58 km/s, and the low-velocity zone is located just between the Qilian Mountain and the Hexi Corridor. ④ The depths of the lower crust imply that the Moho depth is 54 km in the Qilian Mountain, 53.5~53.0 km in the Minle basin and 52 km in the Alxa block, and that there obviously exists a low-velocity layer of 6.5 km/s at the depth of 34~42 km. The research results show that the Longshou Mountain fault may be a reverse one in the upper crust and the Changma-Ebo fault is probably a vertical one reaching the middle crust.
The 3-D velocity tomography image of central Hexi Corridor was obtained by the joint inversion of 3-D velocity structure and focal parameters based on the S-P data of micro-earthquakes recorded by the digital seismic network. The inversed layering velocity structure does reflect some important features of the deep structure in the study area: ① The velocity of shallow deposition is about 5.00~6.15 km/s and the vertical velocity gradient is close to 0.15 km/s; the depth of the crystalline basement is about 7 km, with the velocity being 6.15 km/s. ② The depth of the upper crust is some 18 km, with the velocity being 6.33 km/s; the velocity of Minle basin is slightly higher than that of the North Qilian Mountain and the Longshou Mountain. The Alxa block is obviously thrusting under the Hexi Corridor. ③ The bottom of the middle crust is about 30 km in depth with the velocity being 6.58 km/s, and the low-velocity zone is located just between the Qilian Mountain and the Hexi Corridor. ④ The depths of the lower crust imply that the Moho depth is 54 km in the Qilian Mountain, 53.5~53.0 km in the Minle basin and 52 km in the Alxa block, and that there obviously exists a low-velocity layer of 6.5 km/s at the depth of 34~42 km. The research results show that the Longshou Mountain fault may be a reverse one in the upper crust and the Changma-Ebo fault is probably a vertical one reaching the middle crust.
引文
董治平.1989.民乐盆地活断裂与潜在地震危险区的分析.内陆地震,3(2):129~135.
董治平,赵广昆,马尔曼,等.2004.2003年10月25日甘肃民乐—山丹6.1、5.8级地震.甘肃科学学报,16(3):49~53.
董治平,赵仪泉,慕文斋,等.2005.1954年山丹71/4级地震概述.西北地震学报,27(增刊):19~25.
国家地震局地质研究所,国家地震局兰州地震研究所.1993.祁连山—河西走廊活动断裂系.北京:地震出版社.
李清河,张元生,涂毅敏,等.1998.祁连山—河西走廊地壳速度结构及速度与电性的联合解释.地球物理学报,41(2):197~209.
彭聪.2005.中国西部布格重力异常特征和地壳密度结构.地球学报,26(5):417~422.
石特临,汤泉,李清河,等.1994.河西祁连山中段地震危险基础研究.北京:地震出版社.
杨文采.1997.地球物理反演的理论与方法.北京:地质出版社,112~261.
张必敖,赵文星,朱佐全.1992.河西走廊地区地壳低阻层及其与地质构造和地震活动的关系.西北地震学,14(增刊):66~71.
张元生,李清河,徐果明.1998.联合利用走时与波形反演技术研究地壳三维速度结构(Ⅰ)—理论与方法.西北地震学报,20(2):8~15.
张元生,李清河,刘耀炜,等.2003.地震层析成像软件.西北地震学报,25(2):170~174.
张元生,周民都,荣代潞,等.2004.祁连山中东段地区三维速度结构研究.地震学报,26(3):247~255.
Dong Zhiping.1989.Analysis of the active fault and potential earthquakerisk zone in Minle basin.Inland Earthquake,3(2):129~135(inChinese with English abstract).
Dong Zhiping,Zhao Guangkun,Ma Erman,et al.2004.The earth-quakes of M6.1and M5.8occurring on October25,2003in Minle-Shandan,Gansu province.Journal of Gansu Sciences,16(3):49~53(in Chinese with English abstract).
Dong Zhiping,Zhao Yiquan,Mu Wenzhai,et al.2005.Outline of theShandan earthquake of Ms71/4in Gansu province on February111954.Northwestern Seismological Journal,27(Suppl):19~25(in Chinese with English abstract).
Institute of Geology and Lanzhou Institute of Seismology,State Seismolog-ical Burean.1993.The Qilian Mountain-Hexi Crridor active faultsystem.Beijing:Seismological Press(in Chinese).
Koch M.1993a.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅰ.De-velopment,validation and optimal regularization of the method.Geophys J.Int.,112:385~412.
Koch M.1993b.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅱ.Ap-plication to the northern Rhine Graben/Rhanish Massif Region,Germany.Germany,Geophys J.Int.,112:413~428.
Koch M.1993c.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅲ.Ap-plication to the southern Rhine Grabern,Germany.Geophys J.Int.,112:429~447.
Li Qinghe,Zhang Yuansheng,Tu Yimin,et al.1998.The combined in-terpretation of crustal velocity and electrical resistivity in QilianshanMountain-Hexi Corridor region.Chinese J.Geophys,41(2):197~209(in Chinese with English abstract).
Peng Cong.2005.Bouguer anomalies and crustal density structure inWestern China.Acta Geoscientica Sinica,26:417~422(in Chi-nese with English abstract).
Shi Telin,Tang Quan,Li Qinghe,et al.1994.Background research onseismic risk in the middle segment of Qilian Mountain-Hexi Corri-dor.Beijing:Seismological Press(in Chinese).
Yang Wencai.1997.Theory and methods of geophysical inversion.Bei-jing:Geological Publishing House,112~261(in Chinese).
Sambridge M.1992.Genetic algorithms in seiemic waveform inversion.Geophy J.Int.,109:323~342.
Zhang Biao,Zhao Wenxing,Zhu Zuoquan,et al.1992.Low-resistivity layer at crustal bottom of Hexi Corridor region and its relation to ge-ological structures and seismicity.Seismological Journal,14(Sup-pl):66~71(in Chinese with English abstract).
Zhang Yuansheng,Li Qinghe,Xu Guoming.1998.Combined inversiontechnique to study3-D crustal velocity structure by using seismicwave travel-time and wave form(Ⅰ)-Theory and method.North-western Seismological Journal,20(2):8~15(in Chinese withEnglish abstract).
Zhang Yuansheng,Li Qinghe,Liu Yaowei,et al.2003.The seismictomography software.Northwestern Seismological Journal,25(2):170~174(in Chinese with English abstract).
Zhang Yuansheng,Zhou Mindu,Rong Dailu,et al.2004.3-D velocitystructure in the central-eastern part of Qilianshan.Acta Seismologi-ca Sinica,17(3):272~281(in Chinese with English abstract).
董治平,赵广昆,马尔曼,等.2004.2003年10月25日甘肃民乐—山丹6.1、5.8级地震.甘肃科学学报,16(3):49~53.
董治平,赵仪泉,慕文斋,等.2005.1954年山丹71/4级地震概述.西北地震学报,27(增刊):19~25.
国家地震局地质研究所,国家地震局兰州地震研究所.1993.祁连山—河西走廊活动断裂系.北京:地震出版社.
李清河,张元生,涂毅敏,等.1998.祁连山—河西走廊地壳速度结构及速度与电性的联合解释.地球物理学报,41(2):197~209.
彭聪.2005.中国西部布格重力异常特征和地壳密度结构.地球学报,26(5):417~422.
石特临,汤泉,李清河,等.1994.河西祁连山中段地震危险基础研究.北京:地震出版社.
杨文采.1997.地球物理反演的理论与方法.北京:地质出版社,112~261.
张必敖,赵文星,朱佐全.1992.河西走廊地区地壳低阻层及其与地质构造和地震活动的关系.西北地震学,14(增刊):66~71.
张元生,李清河,徐果明.1998.联合利用走时与波形反演技术研究地壳三维速度结构(Ⅰ)—理论与方法.西北地震学报,20(2):8~15.
张元生,李清河,刘耀炜,等.2003.地震层析成像软件.西北地震学报,25(2):170~174.
张元生,周民都,荣代潞,等.2004.祁连山中东段地区三维速度结构研究.地震学报,26(3):247~255.
Dong Zhiping.1989.Analysis of the active fault and potential earthquakerisk zone in Minle basin.Inland Earthquake,3(2):129~135(inChinese with English abstract).
Dong Zhiping,Zhao Guangkun,Ma Erman,et al.2004.The earth-quakes of M6.1and M5.8occurring on October25,2003in Minle-Shandan,Gansu province.Journal of Gansu Sciences,16(3):49~53(in Chinese with English abstract).
Dong Zhiping,Zhao Yiquan,Mu Wenzhai,et al.2005.Outline of theShandan earthquake of Ms71/4in Gansu province on February111954.Northwestern Seismological Journal,27(Suppl):19~25(in Chinese with English abstract).
Institute of Geology and Lanzhou Institute of Seismology,State Seismolog-ical Burean.1993.The Qilian Mountain-Hexi Crridor active faultsystem.Beijing:Seismological Press(in Chinese).
Koch M.1993a.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅰ.De-velopment,validation and optimal regularization of the method.Geophys J.Int.,112:385~412.
Koch M.1993b.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅱ.Ap-plication to the northern Rhine Graben/Rhanish Massif Region,Germany.Germany,Geophys J.Int.,112:413~428.
Koch M.1993c.Simultaneous inversion for3-D crustal structure and hy-pocentres including direct,refracted and reflected phases-Ⅲ.Ap-plication to the southern Rhine Grabern,Germany.Geophys J.Int.,112:429~447.
Li Qinghe,Zhang Yuansheng,Tu Yimin,et al.1998.The combined in-terpretation of crustal velocity and electrical resistivity in QilianshanMountain-Hexi Corridor region.Chinese J.Geophys,41(2):197~209(in Chinese with English abstract).
Peng Cong.2005.Bouguer anomalies and crustal density structure inWestern China.Acta Geoscientica Sinica,26:417~422(in Chi-nese with English abstract).
Shi Telin,Tang Quan,Li Qinghe,et al.1994.Background research onseismic risk in the middle segment of Qilian Mountain-Hexi Corri-dor.Beijing:Seismological Press(in Chinese).
Yang Wencai.1997.Theory and methods of geophysical inversion.Bei-jing:Geological Publishing House,112~261(in Chinese).
Sambridge M.1992.Genetic algorithms in seiemic waveform inversion.Geophy J.Int.,109:323~342.
Zhang Biao,Zhao Wenxing,Zhu Zuoquan,et al.1992.Low-resistivity layer at crustal bottom of Hexi Corridor region and its relation to ge-ological structures and seismicity.Seismological Journal,14(Sup-pl):66~71(in Chinese with English abstract).
Zhang Yuansheng,Li Qinghe,Xu Guoming.1998.Combined inversiontechnique to study3-D crustal velocity structure by using seismicwave travel-time and wave form(Ⅰ)-Theory and method.North-western Seismological Journal,20(2):8~15(in Chinese withEnglish abstract).
Zhang Yuansheng,Li Qinghe,Liu Yaowei,et al.2003.The seismictomography software.Northwestern Seismological Journal,25(2):170~174(in Chinese with English abstract).
Zhang Yuansheng,Zhou Mindu,Rong Dailu,et al.2004.3-D velocitystructure in the central-eastern part of Qilianshan.Acta Seismologi-ca Sinica,17(3):272~281(in Chinese with English abstract).
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