【摘要】 2014年8月3日云南鲁甸发生M_s6.5地震,震源机制显示该地震为左旋走滑型,断层破裂面以北西向为主,与昭通断裂带近乎垂直.本文基于三维重力反演技术,采用Crust1.0地壳结构模型和最新Moho面深度模型联合约束,反演得到了该地震震源区及周边的三维密度结构特征.反演结果表明:鲁甸地震震源区南北两侧块体运动受到昭通断裂不同程度阻隔,在地质时间尺度上,昭通断裂北段地壳物质运移的阻挡能力相比南段更强.通过进一步调查距离震中较近的流动重力测点的点值变化发现,从2014年3月至2014年6月大海村(P1)重力点值减小,减小幅度达到19μGal,而位于昭通断裂东北侧的江底(P5)重力点值同期变化显示为增加,其他距离较远测点在震前重力变化不明显.综上结果对鲁甸地震的成因机制给出了初步解释.本文结果对于认识孕震区深部结构及地球物理场时空变化特征具有一定的意义.对识别与局部重力变化有关的地震前兆也同样具有参考意义.更多还原

【Abstract】 The August 3,2014,Ludian,Yunnan,Ms6.5 earthquake which focal mechanism is the left-lateral slip.The rupture surface of earthquake is the NW direction and almost perpendicular to Zhaotong fault.In our study,we used the 3D gravity inversion approach to inverse 3D density structure,and made a high-quality reference model as initial model with the Crust 1.0 and the newest Moho relief derived by ChinArray project.The 3D density structure shows that the block movement located at the south and north part of Ludian earthquake had been resisted by the Zhaotong fault(ZTF)in the geological time scale,respectively.The resisted ability of north part ZTF is stronger than the south part.Furthermore,we found the significance decrease of gravity field at the Dahaichun(P1)from Oct.2012 to Jun.2014.But the gravity change of Jiangdi(P5)measurement point shows the increase tendency.The significant gravity change can’t be found at the other points.At last,we give a seismogenic model by the gravity approach.Our results are very important to understand the deep structure of seismogenic region,and also like the key to find the seismic precursor which related to the local gravity change.更多还原