龙门山断裂带地壳结构的三维建模

Three-dimensional modeling of the crust structure of Longmenshan fault zone

为了实现龙门山区域地质信息的科学管理与共享,推动该区域地球物理资料的统一管理,本文在整理现有二维地球物理探测数据的基础上构造了龙门山断裂带区域的三维地壳结构模型,并结合实测的布格重力异常数据对模型进行了分析。结果表明,地层模型正演的整体重力场与实测布格重力异常基本吻合,初步证明该模型的正确性。局部重力场显示:在该模型的尺度下,沉积层对整体重力场的变化贡献较小;中上地壳有不同程度的隆起和坳陷,与前人研究所揭示的低速异常体吻合;地幔表现为规则的自西北至东南单调上升的重力异常梯度带,与前人反演结果的趋势一致,从而证明了模型的可靠性。最后在重力资料约束下对模型进行了反演,进一步修正了模型。

3D geological modeling can realize the intuitive and complete expression of the spatial relationship among geological bodies,therefore it is an effective way to achieve the scientific management and sharing of geological information. At the same time,a well-established 3D model supports slices in any direction,which can predict the shape of unknown areas and infer structural history. This paper constructed a 3D crustal structure model of the Longmenshan fault zone by collating existing 2D geophysical data,and analyzed the model with the measured Bouguer gravity anomaly data. The result show that the overall gravity field of the formation model is basically consistent with the measured Bouguer gravity anomalies,which preliminary proves the correctness of the model. The local gravity field shows that the sedimentary layer contributes less to the change of the overall gravity field with the scale of the model. The middle and upper crust develops uplifts and depressions to different degree,which coincides with the existence of low-velocity anomalies revealed by previous researches. The gravity anomaly gradient zone regular monotonously rises from northwest to southeast,which is consistent with the trend from previous inversion results,thus basically proving the reliability of the model.Furthermore,we do model inversion under the constraint of gravity data,and the model was modified.