青藏高原中段现今构造应力场的数值模拟

NUMERICAL MODELING OF THE PRESENT TECTONIC STRESS FIELD IN THE CENTRAL QINGHAI-TIBET PLATEAU

将地壳岩石看成粘性流体,对青藏高原中段进行了构造应力场和速度场的有限元模拟。模拟结果表明:青藏高原总体向北和向东位移,向北的位移速度是南部最大,由南向北逐渐减小;向东的位移速度以唐古拉断裂附近最大,南北两侧逐渐减小,形成“挤出”现象。最大主应力方向在南部以NNW向为主,北部以NNE向为主,总体为近SN向。将模拟结果与构造勘察、地震活动和GPS测量结果进行了对比,它们具有很好的一致性,良好地揭示了青藏高原构造活动规律、断层活动强度和东向位移的驱动机理,青藏高原现今活动是印度板块向北推挤和深部物质东流共同作用的结果。

Considering crustal rocks as viscous fluids, the tectonic stress field and velocity field of the central segment of the Qinghai-Tibet Plateau are modeled by using the finite element method. The results of modeling indicate that the Qinghai-Tibet Plateau is generally displaced toward the north and east. The velocity of north-directed displacement is highest in the south and gradually decreases form south to north. The velocity of east-directed displacement is highest near the Tanggula fault and gradually decreases toward the south and north sides, showing an ＂extrusion phenomenon＂. The maximum principal stress is oriented mainly in a NNW direction in the south and in a NNE direction in the north, generally in a N-S direction. Comparison of the modeling results with the results of tectonic survey and earthquake activity and GPS measurements shows that they are in good agreement. This well reveals the characteristics of tectonic activity, intensity of fault activity and driving mechanism of east-directed displacement in the Qinghai-Tibet Plateau. The present activity of the Qinghai-Tibet Plateau is the results of combined action of northward push and compression of the Indian plate and eastward flow of deep materials.