澜沧江流域重大水电工程地区地震层析成像
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摘要
根据云南区域地震台网记录的地震观测资料,使用澜沧江流域周边40个地震台记录到的3600多个地震的近25000条P波和S波波形数据,采用层析成像理论,反演了云南澜沧江流域地区的三维速度结构图,结果表明,上地壳速度异常分布与地表地质断裂构造有关。以澜沧江断裂为界,西侧大部分地区表现为速度负异常,扰动值在-2·0%~-4·0%;东侧大部地区为速度正异常。在30km深的剖面上,澜沧江流域西南出现一条近北东走向的负速度异常带,这可能与南汀河深大断裂有关;在45km和65km深度以下的剖面上,同样出现与澜沧江断裂和红河断裂有关的速度负异常带,并且澜沧江断裂北段与南段速度异常不同,北段总体表现为负异常,南段则表现为正异常。腾冲火山地热区从地表至地幔均出现低速异常,表明地幔热物质参与了腾冲火山的活动。研究区域层析成像三维速度异常分布揭示了澜沧江流域地球内部状态的某些特征,为澜沧江流域重大梯级电站的水库诱发地震机理研究与地震预测提供了地球内部介质结构的深部背景。
According to the observational data from the Yunnan Regional Seismic Network, we inversed the 3-D velocity structure along the Lancangjiang Basin area using about 25000 P-wave and S-wave waveforms of more than 3600 earthquakes recorded by 40 seismic stations around the area on the basis of tomography theory. The results indicate that the velocity anomaly distribution in the upper crust is related to the geological faults on the surface. Taking the Lancangjiang fault as boundary, most of the areas in the west show negative velocity anomaly and have a disturbance value between -2.0% and -4.0%; While in the east of the fault appears a positive velocity anomaly. On the 30-km-deep profile, a negative velocity anomaly belt striking near NE appears on the southwestern side of the Lancangjiang Basin, which is probably related to the Nantinghe deep fault. The same way, on the 45- and 65-km-deep profiles also appear the negative velocity anomalies related to the Lancangjiang and Honghe faults. Furthermore, the velocity anomalies in the north and south segments of the Lancangjiang fault are different. As a whole, the negative anomaly appears in the north segment and the positive one does in the south. The low velocity anomaly appears in the Tengchong volcano geoheat area from the surface to the mantle, indicating the heating materials have joined in the activity of the Tengchong volcanoes. The 3-D velocity anomaly distribution of the tomography in the studying area reveals some characteristics of the earth's interior state along the Lancangjiang Basin, which provides the deep background of the earth's interior structures for the mechanism of the reservoir induced earthquake of the key series of power stations along the Lancangjiang Basin and earthquake forecast.
According to the observational data from the Yunnan Regional Seismic Network, we inversed the 3-D velocity structure along the Lancangjiang Basin area using about 25000 P-wave and S-wave waveforms of more than 3600 earthquakes recorded by 40 seismic stations around the area on the basis of tomography theory. The results indicate that the velocity anomaly distribution in the upper crust is related to the geological faults on the surface. Taking the Lancangjiang fault as boundary, most of the areas in the west show negative velocity anomaly and have a disturbance value between -2.0% and -4.0%; While in the east of the fault appears a positive velocity anomaly. On the 30-km-deep profile, a negative velocity anomaly belt striking near NE appears on the southwestern side of the Lancangjiang Basin, which is probably related to the Nantinghe deep fault. The same way, on the 45- and 65-km-deep profiles also appear the negative velocity anomalies related to the Lancangjiang and Honghe faults. Furthermore, the velocity anomalies in the north and south segments of the Lancangjiang fault are different. As a whole, the negative anomaly appears in the north segment and the positive one does in the south. The low velocity anomaly appears in the Tengchong volcano geoheat area from the surface to the mantle, indicating the heating materials have joined in the activity of the Tengchong volcanoes. The 3-D velocity anomaly distribution of the tomography in the studying area reveals some characteristics of the earth's interior state along the Lancangjiang Basin, which provides the deep background of the earth's interior structures for the mechanism of the reservoir induced earthquake of the key series of power stations along the Lancangjiang Basin and earthquake forecast.
引文
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Hole J A.1992.Nonlinear high-resolution three-dimensional seismictravel time tomography[J].J Geophys Res,97:6553-6562.
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Thurber C H.1983.Earthquake locations and three-dimensional crustalstructure in the Coyote lake area,Central California[J].J Geo-phys Res,88:8226-8232.
Um J,Thurber C H.1987.Afast algorithmfor two-point seismic tracing[J].Bull Seism Soc Amer.77:927-986.
胡鸿翔,陆涵行,王椿镛,等.1986.滇西地区地震结构的爆破地震研究[J].地球物理学报,29(2):133-144.
阚荣举,赵晋明.1994.腾冲火山地区的壳幔结构[A].见:陈运泰,阚荣举,腾吉文主编.中国固体地球物理学进展[C]北京:海洋出版社:23-30.
刘福田,李强,吴华,等.1989.用于速度图像的层析成像法[J].地球物理学报,(32):46-58.
刘瑞丰,陈培善,李强,等.1990.云南及邻近地区三维速度图像[J].地震学报,15(1):61-67.
林中洋,胡鸿翔,张文彬,等.1993.滇西地区地壳上地幔速度结构特征的研究[J].地震学报,15(4):427-440.
秦嘉政,皇甫岗,李强,等.2000.腾冲火山及邻区速度结构的三维层析成像[J].地震研究,23(2):157-164.
王椿镛,Mooney W D,王溪莉,等.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24(1):1-16.
Hole J A.1992.Nonlinear high-resolution three-dimensional seismictravel time tomography[J].J Geophys Res,97:6553-6562.
Inous H.1990.Whole mantle P-wave travel time tomography[J].PhysEarth Planet Inter,59:294-328.
Thurber C H.1983.Earthquake locations and three-dimensional crustalstructure in the Coyote lake area,Central California[J].J Geo-phys Res,88:8226-8232.
Um J,Thurber C H.1987.Afast algorithmfor two-point seismic tracing[J].Bull Seism Soc Amer.77:927-986.
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