摘要:
首先对由深部地震测深剖面观测结果综合归纳出的一个华北地区岩石圈12层三维非均匀实际模型在承受和不承受来自底面的上拱力条件下的应力场进行了数值模拟计算,并根据计算结果对唐山地震孕震条件及长期前兆进行分析研究。其次,再考虑一个唐山及外围地区含有地表及深部断裂的三维不均匀分层岩石圈模型,不对称的加载方式,用长方体形的硬包体、软包体或软-硬包体来模拟唐山大震的孕震区,采用三维有限元法来计算应力场与位移场,并根据计算结果对唐山地震的前兆场时空演化特征及孕震过程进行了分析讨论。所得的初步分析研究结果表明:(1)唐山地震震源位于华北地壳中的一个较坚固的块体之内;(2)地幔上拱力可能在唐山大震孕育中起较大作用;(3)唐山大震的前兆场时空演化特征可用坚固体(硬包体)孕震模式来得到合理的解释。
Abstract:
At first, based on the observational data of deep seismic sounding, a 12-layered 3-dimensionai heterogeneous model of the upper lithosphere of North China was established, and the stress fields under the condition of an upwarp force effecting to basement and under the condition without such an upwarp force have been calculated by using the three-dimensional finite-element method. On the basis of the numerical simulation, the seismogenic condition and long-term precursor of Tangshan great earthquake were analyzed and researched. Sceondly, one layered 3-dimensional heterogeneous model of the lithosphere of Tangshan region and its vicinity which contains the surface and deep faults was considered. The non-symmetrical load condition was taken. The seismogenic body was simulated by hard inclusion, soft inclusion, and hard-soft inclusion of rectangular shape separately for the different stages of its evolution. The stress and displacement fields have been calculated by using the three -dimensional finite-element method, and based on the results of numerical simulation, the characteristics of temporo-spatial evolution of precursor field and the seismogenic process of Tangshan great earthquake were analyzed and discussed. The results obtained show that: (1) The focus of Tangshan great earthquake was located in a hard block of the crust of North China; (2) The upwarp force effecting to Crust basement from the Upple Mantle may play an important role in seismogenic process; (3) The characteristics of temporo-spatial evolution of precursor field of Tangshan great earthquake can be interpreted rationally by using the strong body earthquake-generating model.
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