| 缅甸山弧地区Benioff带的形态及其应力状态 |
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| 引用本文： | 臧绍先.缅甸山弧地区Benioff带的形态及其应力状态[J].地球物理学报,1987,30(2):144-158. |
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| 作者姓名： | 臧绍先 |
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| 作者单位： | 北京大学地球物理系 |
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| 摘 要： | 研究了缅甸山弧附近的中源地震分布,发现h>70km的地震主要分布在20°N-27°N之间,形成明显的条带分布,24°N以南走向近南北,24°N以北走向逐渐接近NE;通过垂直剖面的研究,发现缅甸山弧下的Benioff带形态是变化的,在南北两端倾角较小,且较为平直,延伸深度浅,小于100km;在地震带的中间部分,Benioff带的倾角逐渐加大,且倾角随深度加深而增大,延伸深度可达180km。在一些剖面上出现双地震层,一般出现在45-100km的深度范围内,两层间的距离从10-25km不等;在同一剖面上,两层间在浅部间距大,在深部间距小。研究了沉降带上的应力状态,发现沉降带上P轴的优势方向位于NE-SW,T轴分布较分散;P、T轴随深度没有明显变化;在上地震层中,T轴明显接近于Benioff带的倾向;通过地壳内及沉降带上地震机制解的对比,发现前者的优势方向相对于后者逆时针旋转了一定角度。
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| 关 键 词： | 沉降带 Benioff带 缅甸山弧 应力状态 |
| 收稿时间： | 1985-07-04 |
THE CHARACTERISTICS OF THE SUBDUCTION ZONE BENEATH THE BURMESE ARC AND ITS STRESS STATE |
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| ZANG SHAO-XIAN.THE CHARACTERISTICS OF THE SUBDUCTION ZONE BENEATH THE BURMESE ARC AND ITS STRESS STATE[J].Chinese Journal of Geophysics,1987,30(2):144-158. |
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| Authors: | ZANG SHAO-XIAN |
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| Affiliation: | Department of Geophysics, Peking University, Beijing |
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| Abstract: | The distribution of the intermediate depth earthquakes in the area of the Burmese arc was studied by using the data from 1. S. C. for the period of 1965-1982. It is found that the earthquakes with depths more than 70 km mainly occurred in the region from 20°N to 26.5°N and formed a seismic belt. The distribution of the earthquakes was studied in detail by examihg seven profiles perpendicular to the seismic belt. It confirms existence of the Benioff Zone Beneath the Burmese, arc. The geometry of the Benioff Zone changes along the seismic belt. Its dip direction is eastward in the south part from 24°N and graduatly changes to nearly south-eastward in the north part. In both southern arid northern ends of the seismic belt the Benioff Zone is nearly straight with a smaller dip angle than that in the middle part of the belt, and it extends to the depth of 100 km. In the middle part of the seismic belt the dip angle of the Benioff Zone graduatly increases with depth aand the Benioff Zone extends to 180 km. In the depths from 45 km to 100 km the double seismic zones appear on some profiles, the distances between the upper and the lower zones are different in different profiles, varying from 10 km to 25 km.The stress state on the subduction zone was studied by using fault plane solutions. It is found that the P axes distribute mainly in the azimuths from 210° to 270° and the T axes do not have a predominant direction. The predominant direction of P axes for earthquakes in the crust is different from the one of earthquakes on the subduction zone, suggesting that the direction of the compression stress in the crust rotates nearly 20° counterclockwise related to that on the subduction zone. The directions of T axes on the upper seismic zone are coincident with the dip direction of the subduction zone. |
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| Keywords: | Subduction zone Benioff Zone Burmese arc Stress state |
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