Abstract: Basing on the fault dislocation model of Yoshimitsu Okada and Steketee and filed scientific investigation,we calculate theoretically space variation of the displacement fields,including vertical and horizontal displacements of the Wenchuan earthquake along the near zone(within 30km to the fault)of Yingxiu-Beichuan reverse fault.In the simulation,we interpret the space variation of the displacement field in the near zone of Yingxiu-Beichuan reverse fault in details.However,we can't describe the space variations in much detail by the field scientific investigation and limited data of GPS stations.Comparing with the results of field science investigation on surface rupture zone,our computational results show that the displacement fields have the same variation trend.At the same time,the displacement field declines drastically with distance to the outcrop of the fault,which agrees with the present research,and the velocity of this decline is much faster on the foot wall of fault than that on the hanging wall.By the simulation,we get the main conclusions:the vertical displacement of ground surface resulting from faulting in the earthquake shows the strong spatial inhomogeneity,and most large values of vertical displacement concentrate on the terminals of the fault,i.e.nearby Yingxiu and Beichuan.The displacement of the ground surface,including horizontal and vertical component,varies more drastically on both terminals of the fault than that of the middle section of the fault.The vertical displacement changes drastically along the direction of strike in the hanging wall of the fault than that of the foot wall.Except on the terminals of the fault,the horizontal displacement distributes homogenously in space.On the whole,except on the terminals of the fault,the amplitude of the displacement field on the hanging wall of the fault is larger than that of the foot wall.

Key words: M_S 8.0 Wenchuan earthquake, dislocation model, fault

摘要： 基于Yoshimitsu Okada及Steketee的断裂位错模型,从理论上反演了汶川地震时龙门山中央主断裂中段附近区域(距离断裂30km)内由断裂逆冲兼右旋错动形成的地表位移场的空间演化,包括地表垂直和水平位移场的基本特征。模拟表明了断裂错动过程中近断裂区域地表位移场的空间演化情况,而该空间演化情况通过野外科考和有限的GPS测站数据是无法细致描述的。文中将模拟结果与野外地表破裂带的科考成果进行比较,发现两者在变化趋势上近似表现一致;且位移场在离开断裂出露处迅速衰减的特征与现有研究成果一致;同时模拟结果也表明位移场的衰减速度在下盘强于上盘。模拟结果最终表明:断裂错动形成的地表垂直位移存在较大的空间不均匀性且较大的幅值主要集中于断裂的两端,即映秀和北川附近,垂直和水平位移场在断裂端部的变化都强于断裂的中部;地表垂直位移沿走向的变化在断裂上盘强于下盘;水平位移除了在断裂两端变化比较剧烈外,在空间上分布比较均匀;总体上,除断裂端部外位移场的幅值在上盘大于下盘。

关键词: 汶川地震, 位错模型, 断裂