【摘要】 应用Yoshimitsu Okada及Steketee静态断裂位错模型及目前汶川地震研究成果,理论上反演龙门山近断裂区域在汶川地震中从震源深处至地表的变形(应变)场分布.通过矢量合成及坐标变换方法将Yoshimitsu Okada单一静态断裂位错模型应用于龙门山断裂带错裂研究中,重点研究汶川地震中因龙门山中央主断裂中、北段和山前断裂中段共同错动形成的应变场.模拟揭示了应变场平面和垂直分量的空间分布特征.研究发现:应变场垂直分量的幅值在震源深处大于地表,但在地表分布范围较大;应变场沿断裂走向分量的幅值和影响范围由震源深度至地表均逐渐增加;应变场垂直于断裂走向分量的变化情况类似于垂直向应变场;震源深度附近的大变形可能为龙门山断裂在地震中强烈挤压形成的塑性变形.研究表明从震源至地表,所有应变场分量从断裂两侧附近位置至远离断裂,幅值均迅速衰减;其中地表部分的最大变形与现有计算成果近似,变形场的变化特征与地表科考近似,断裂两盘变形方向与震后InSAR资料揭示的情况一致.更多还原

【Abstract】 Based on the Yoshimitsu Okada and Steketee s dislocation model and present achievements of scientific researches on Wenchuan earthquake,we theoretically compute the distribution of deformation (strain) fields from the focal depth to ground surface in the region near the Longmenshan faults belt.Through the vector synthesis and coordinate transformation method,we expand Okada s single static dislocation model to the research of Longmenshan faults belt,specially the deformation fields caused by the slide motion of middle and north part of central segment and middle part of foreland segment of Longmenshan fault belt in Wenchuan earthquake.The research shows the spatial distribution features of level and vertical components of deformation fields.Through the simulation,we find that the vertical component of strain field is greater in magnitude but smaller in scope at the focus than that on the ground surface,the strain component along the strike direction increases gradually in both magnitude and influencing scope from focal depth to ground surface,and the variation of strain component perpendicular to the fault strike is similar to that of the vertical component. The large deformation near the focus perhaps stems from the plasticity.Moreover,our simulation also shows the variation of strain field with the distance to the fault outcrop.The simulation result on the ground surface agrees with the present scientific research.At last,by comparing with InSAR observation data,the deformation direction obtained by simulation agrees with the observation data.更多还原