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1976年6月9日云南省龙陵地区发生了一次6.2级余震。本文对这次地震的强震记录进行了数值模拟,并通过合成地震图与观测资料的对比,研究了这次地震的断层长度、破裂方式以及位错分布的特点。分析结果得到这次地震是由北向南的右旋走滑型破裂,断层长度约为20km,破裂速度接近0.9倍剪切波速,断层上的平均错距为60cm,平均应力降约为23bar。近场记录中的丰富高频成分表明断层上的位错分布和上升时间分布是极不均匀的,相应的局部错距和局部应力降分别为189cm和200—300bar,远高于其平均值。通过模拟过程可以看出近场记录对于震源断层的长度和破裂方式等都有较强的约束作用,因此分析强震记录是研究震源过程的一种有效手段。
On June 9, 1976, a 6.2-magnitude aftershock took place in Longling, Yunnan Province. In this paper, the strong earthquake records of this earthquake are numerically simulated. By comparing the synthetic seismograms with the observed data, the fault length, rupture modes and dislocation distribution of this earthquake are studied. The results show that the earthquake is a dextral strike-slip rupture from north to south with a fault length of about 20km and a rupture velocity close to 0.9 times shear wave velocity. The average fault offset is 60cm and the average stress drop is about 23bar. The abundance of high-frequency components in near-field records indicates that the dislocation distribution and rise time distribution on the fault are extremely inhomogeneous, with corresponding local errors and local stress drops of 189 cm and 200-300 bar, respectively, much higher than their average values. It can be seen from the simulation that near-field recording has a strong constraint on the length of the source fault and the mode of rupture. Therefore, the analysis of strong earthquake records is an effective method to study the source process.