用复合型法反演震源破裂过程的研究
A STUDY ON THE INVERSION OF RUPTURE PROCESS BY USING THE COMPOUND MODEL METHOD
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摘要: 本文探讨了用P波频谱研究不对称双侧破裂方式与正交破裂方式的方法,研究了用复合型法反演震源参数的可行性。 用这种方法反演了1966年3月8日邢台马兰6.8级地震及1966年3月22日东旺6.7级地震的震源参数。通过与用网格尝试法反演的结果及余震分布等进行比较,认为这种反演方法除了与过去的网格尝试法类似,可以得到最优拟合参数解外,还可以大大减少计算量,实现了网格尝试法难以实现的更复杂的震源模式的反演。 本文还用此方法研究了1962年3月19日广东河源6.1级地震及1969年7月26日广东阳江6.4级地震的破裂过程。研究结果表明:河源地震的破裂方式是正交三侧破裂。北西方向为主破裂,破裂长度8km,破裂速度0.6km/s. 南东方向破裂长度较短,约2km,破裂速度2.0km/s.正交侧指向南西,破裂长度3km,破裂速度0.5km/s,这个结果与余震分布图所显示的图象很相象。阳江地震的破裂方式是不对称双侧破裂。主破裂方向为北东东,破裂长度14km,破裂速度0.8km/s;朝南西西向的破裂长度5km,破裂速度0.6km/s。Abstract: In this paper, we discuss the method of studying the asymmetrical bilateral and the orthogonal ruptures of the earthquake source by using spectral amplitudes of P wave displacement, also the feasibility of the inversion about parameters of source by using the compound model method. Using this method we have calculated the rupture processes for the Malan earthquake with Ms = 6.8 of March 8, 1966 and the Dongwang earthquake with Ms = 6.7 of March 22, 1966 in the Xingtai region. In the comparison of the above results with that calculated by using the grid trial method and the distribution of aftershocks it is shown that in addition to the similarly to the grid trial method used before, by this method it is able to obtain a solution for the optimum fitting parameters; this method of inversion can also reduce the computation greatly and further achieve more complicated inversion of the source model, which was very difficult for the grid trial method to deal with.The rupture processes of the Heyuan earthquake (M = 6.1), of March 19, 1962 (Guangdong Province) have also been studied by using this method It is shown by the results that: the rupture process of the Heyuan earthquake is orthogonal and trilateral with the principal rupture striking NW, a rupture length of 8 km and a rupture velocity of 0.6 km/s. The rupture in the SE direction is shorter, which is about 2 km in length with a velocity of 2.0 km/s. The orthogonal branch extended towards SW and is about 3 km in length with a velocity or 0.5 km/s. This result is very similar to the pattern shown by the distribution of aftershocks. The way of rupture of the Yangjiang earthquake is asymmetrical and bilateral, and the direction of the principal rupture is ENE with a length of about 14km and a velocity of about 0.8 km/s. The rupture in the direction of WSW is only about 5km in length, with a velocity of rupture of about 0.6 km/s.