Earthquake mechanisms in the Himalayan, Burmese, and Andaman Regions and continental tectonics in central Asia
Earthquake mechanisms in the Himalayan, Burmese, and Andaman Regions and continental tectonics in central Asia
复制标题
喜马拉雅、缅甸和安达曼地区的地震机制与中亚大陆构造
DOI：
10.1029/jb075i014p02699
复制
发表时间：
1970
期刊：
影响因子：
--
通讯作者：
T. Fitch
中科院分区：
文献类型：
--
作者：
T. Fitch
提出了兴都库什和苏门答腊之间13次地震的震源机制，包括沿喜马拉雅山前的4次浅源地震和缅甸山脉下的2次中深度地震。所有机制都是基于长周期仪器记录的初动P波和s波数据。喜马拉雅前缘构造机制证实了逆冲断裂的存在，并有中生代后的地质证据。中亚逆冲断层的其他证据来自俄罗斯研究人员最近发表的基于其他地震数据的震源机制。缅甸山脉下面中间深度的最小压缩轴（T轴）大致沿着地震带的倾斜方向，其他几个地震带中间深度的T轴也是如此。从中国西部两次浅层地震中得到了一个与走滑断裂一致的机制解和一个与正断层一致的机制解。喜马拉雅山区内的一次浅层地震产生了正常的断层机制，西缘的一次地震和安达曼海北部边界附近的两次地震也产生了正常的断层机制。与喜马拉雅山下逆冲运动相一致的滑动矢量具有几乎均匀的北至东北走向。这一证据以及大震级地震发生的频率表明，浅层地震滑动可能解释了印度洋和欧亚板块沿喜马拉雅山前的汇聚。
Focal mechanisms are presented for thirteen earthquakes between Hindu Kush and Sumatra, including four shallow-focus events along the Himalayan mountain front and two events at intermediate depth beneath the Burmese mountains. All mechanisms are based on first-motion P- and S-wave data recorded by long-period instruments. The mechanisms along the Himalayan front confirm the existence of thrust faulting for which there is post-Mesozoic geologic evidence. Additional evidence for thrust faulting in central Asia comes from focal mechanisms based on other seismic data published recently by Russian investigators. The axis of minimum compression (the T axis) at intermediate depths beneath the Burmese mountains is oriented approximately down the dip of the seismic zone, as are T axes at intermediate depths in several other seismic zones. A mechanism solution consistent with strikeslip faulting and another consistent with normal faulting were derived from two shallow earthquakes in western China. One shallow earthquake within the Himalayas yielded a normal faulting mechanism, as did one event from the western margin and two events near the northern border of the Andaman Sea. Slip vectors consistent with underthrusting beneath the Himalayas have a nearly uniform north to northeasterly strike. This evidence, as well as the frequency of occurrence of large-magnitude earthquakes, suggests that seismic slip at shallow depths may account for the convergence between the Indian Ocean and the Eurasian plates along the Himalayan mountain front.