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本文给出龙陵地震序列的应力场分布及发震断裂的分析结果。龙陵震区的区域构造背景是三条断裂所包围的三角形块体,龙陵地震序列发生在这个块体的内外。在此块体内外,地震机制有明显差别:在块体内部,大震及强余震主压应力轴方位以北北西为主,与区域应力场不一致,有一个相当大的夹角;在块体外面,强余震主压应力轴方位均为北北东,与区域应力场一致。 龙陵大震及强余震的发震断裂走向在块体内外也完全不同,并组成“”形格架。在块体内部,主震及强余震的发震断裂为北北东及北东东,在块体以外(北部)为北北西向。龙陵两个大震的发震断裂都在块体内部的规模相当小的次级断裂上,它们都不在任何一个边界断裂上。龙陵大震不是发生在大陆内部块体边界的地震,而是发生在块体内部的地震。这种震例是少见的。 作者强调指出,龙陵地震无论其区域构造背景、发震断裂分布、应力场分布及余震序列的时空发展、烈度分布、裂缝带、地表形变等实际资料均十分复杂,极具特色,是国内外少有的震例。
This paper gives the stress field distribution of the Longling earthquake sequence and the analysis results of seismogenic faults. The regional tectonic setting of the Longling earthquake zone is a triangular block surrounded by three faults, and the Longling earthquake sequence takes place inside and outside this block. In this block, there are obvious differences in the earthquake mechanism: in the block, the major compressional and strong aftershocks are dominated north and west of the principal compressive stress axis, which is not consistent with the regional stress field and has a fairly large angle; Outside, the major aftershock principal compressive stress axis azimuths are north and east, consistent with the regional stress field. Longling earthquake and strong aftershocks of the earthquake fracture in the body is completely different inside and outside, and form a “” -shaped frame. In the interior of the block, the seismogenic faults of the main and strong aftershocks are north and east and east, and north and south west of the block (north). The seismogenic faults of the two large earthquakes in Longling are all on the relatively small secondary faults inside the block, neither of which is on any boundary fault. The great earthquake in Longling is not an earthquake occurring on the boundary of the block within the continent, but an earthquake occurring inside the block. This earthquake is rare. The author emphasizes that the actual data of the Longling earthquake, regardless of its regional tectonic setting, the distribution of seismogenic faults, the distribution of stress field and the aftershock sequences, have very complicated and distinctive characteristics such as intensity distribution, fracture zone and surface deformation. Rare earthquake cases.