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对于天然地震的成因研究多关注于板块相互作用以及流体、断裂等因素.震区地壳结构本身的不稳定性是发生地震的重要因素.伽师地区位于塔里木盆地西端,为塔里木地块、天山造山带、西昆仑造山带、帕米尔构造结的交接部位,具有典型的地壳结构不稳定性,地震频发.地震宽角反射/折射、近垂直反射等地震资料显示伽师地区地壳结构具有特殊的不稳定性.地震宽角反射/折射资料提供了盆地约75 km以上的二维速度结构剖面,地壳速度结构较为复杂,可以识别出高速块体和低速块体相间与堆叠的形态.近垂直地震反射剖面展示了20 s双程到时深度以上更为精细的结构特征,盆地盖层为成层性较好的反射,反射事件C,D构成了地壳之下的稳定带,而反射事件A,B,E则为地壳不稳定结构.建立了伽师地区地壳结构不稳定性的模型,地壳高速块、低速块(即刚性强、弱)相间并堆叠构成的不稳定带置于反射事件C,D构成的稳定带之上,挤压作用与近垂直的隐伏断裂加剧了这种不稳定性.地壳结构不稳定是导致天然地震的重要因素,同样表现存在于日本列岛以及鄂尔多斯盆地等地.
The study on the causes of natural earthquakes mostly focuses on the plate interaction and fluid, fracture, etc. The instability of the crustal structure in the earthquake zone is an important factor in the earthquake.The Jiashi area is located at the western end of the Tarim Basin, which is the Tarim block, Belt, the West Kunlun orogenic belt and the junction of the Pamir structural knot, with typical crustal structural instability and frequent earthquakes. Seismic wide-angle reflections / refractions and near-vertical reflections show that the crustal structure in the Jiashi area has a special Instability.The seismic wide-angle reflection / refraction data provide a 2D velocity structure profile of about 75 km above the basin, and the crustal velocity structure is more complex, which can identify the interphase and stacking patterns of high-velocity blocks and low-velocity blocks. The reflection profile shows a more elaborate structural feature at 20 s two-way-to-arrival depth. The basin cover is a well-stratified reflection and reflection event C and D which form a stable zone below the crust. The reflection events A, B, and E are the unstable crustal structures.A model of crustal structural instability in the Jiashi area was established, and the crustal high-velocity blocks and low-velocity blocks (ie, strong and weak) were interlaced and stacked The instability zone is placed above the stability zone formed by the reflection events C and D. The extrusion and near-vertical concealed faults aggravate this instability.The instability of crustal structure is an important factor leading to natural earthquakes, Exist in the Japanese archipelago and the Ordos Basin and other places.