Seismicity, gravity, and tectonics of northeast India and northern Burma
Seismicity, gravity, and tectonics of northeast India and northern Burma
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印度东北部和缅甸北部的地震活动、重力和构造
DOI：
10.1785/bssa0660051683
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发表时间：
1976
影响因子：
3
通讯作者：
M. Ahluwalia
中科院分区：
文献类型：
--
作者：
R. K. Verma;M. Mukhopadhyay;M. Ahluwalia
实际上，整个印度东北部和缅甸北部都具有异常重力场和高地震活动区的特征。该地区的布格异常变化范围从西隆高原的+44 mgals到阿萨姆谷北Lakhimpur附近的-255 mgals。这些区域的等静压异常 (Hayford) 变化范围为 +100 至 -130 mgals。若开山和缅甸平原上空的均衡异常范围为 -20 mgals 至 -100 mgals。
该地区地震高发区包括喜马拉雅东部（包括阿萨姆邦构造）、若开-耀玛（包括特里普拉邦褶皱带）、伊洛瓦底江盆地、西隆高原、道基断层和孟加拉盆地北部。异常的重力和地震活动与该地区主要发生在白垩纪和新生代时期、由于印度、青藏和缅甸板块相互作用而发生的大规模构造运动有关。高地震活动表明运动仍在继续。缅甸下方的地震带大致呈 V 形，在若开-耀玛下方向东倾斜。缅甸的大多数中震源地震都位于负均衡异常区域的下方，这表明若开-佑玛和缅甸平原下方可能存在俯冲带。
西隆高原自白垩纪以来就有垂直隆起的历史。如果这一说法属实，那么高原的隆起早于喜马拉雅构造运动，始于 20 至 30 米。在印度大陆与欧亚板块发生牢固接触之前。该高原的特点是大的正均衡异常以及高地震活动性。正均衡异常可能是由于地幔中的碱性物质侵入或并入高原下方的地壳所致。这些侵入可能是通过道基断层等深层断层发生的，也可能是其隆起的原因。
Practically the whole of northeastern India and northern Burma is characterized as an anomalous gravity field as well as an area of high seismicity. The Bouguer anomaly in the region varies from +44 mgals over Shillong Plateau to −255 mgals near North Lakhimpur in Assam Valley. Isostatic anomaly (Hayford) varies from +100 to −130 mgals in these areas. Over Arakan-Yoma and the Burmese plains, the isostatic anomalies vary from −20 mgals to −100 mgals.
Regions of high seismicity in the area include the eastern Himalaya (including Assam syntaxis), Arakan-Yoma including the folded belt of Tripura, Irrawaddy basin, Shillong Plateau, Dauki fault and the northern part of Bengal basin. The abnormal gravity and seismicity are related to large scale tectonic movements that have taken place in the area mostly during the Cretaceous and Cenozoic times, due to interaction of the Indian, Tibetan, and Burmese plates. The high seismicity indicates that the movements are continuing. The seismic zone underlying Burma is approximately V shaped and dips toward the east underneath Arakan-Yoma. Most of the intermediate-focus earthquakes in Burma underlie the area characterized by negative isostatic anomalies, indicating the probable existence of a subduction zone underneath the Arakan-Yoma and the Burmese plains.
The Shillong Plateau has a history of vertical uplift since Cretaceous times. Provided this statement is true, the uplift of the plateau preceded Himalayan tectonics starting 20 to 30 m.y. before continental India made solid contact with the Eurasian plate. The plateau is characterized by large positive isostatic anomalies as well as high seismicity. The positive isostatic anomalies may be due to intrusion or incorporation of basic material from the mantle into the crust underlying the Plateau. These intrusions may have taken place through deep seated faults such as the Dauki and could be responsible for its uplift as well.