A STUDY ON THE INVERSION OF RUPTURE PROCESS BY USING THE COMPOUND MODEL METHOD

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.