文摘
The moment tensor solution, source time function and spatial-temporal rupture process of the M s6.4 earthquake, which occurred in Ning’er, Yunnan Province, are obtained by inverting the broadband waveform data of 20 global stations. The inverted result shows that the scalar seismic moment is 5.51×1018 Nm, which corresponds to a moment magnitude of M W 6.4. The correspondent best double couple solution results in two nodal planes of strike 152°/dip 54°/rake 166°, and strike 250°/dip 79°/ rake 37°, respectively. Considering the isoseismals and geological structures in the meizoseismal region, the first nodal plane (strike 152°/ dip 54°/ rake 166°) is preferred to be the seismogenic fault. Thus, the M s6.4 earthquake occurred mainly along a right-lateral fault striking 152°. The source time function shows that the duration time of the earthquake is about 14 s. The most of the energy releases within the first 11 s and in 11-4 s the rupture is weak. The snapshots of the slip-rate indicate that the rupture process has 3 more detailed stages. In the first stage of the first 4 s after rupture initiation, the rupture propagates simultaneously toward both strike and dip directions; in the second stage of the following 3 s, the rupture extends to down-dip direction; and in the third stage, the rupture looks to be scattering on the fault. In general, this earthquake is of bilateral rupture, and the rupture mainly takes place in strike-dip direction. The major ruptured area is in the shape of a diamond with a dimension of 19 km. On the whole fault plane, the maximum slip is about 1.2 m, the average slip is about 0.1 m, the maximum slip-rate is 0.4 m/s and the average slip-rate is 0.1 m/s. The features of the co-seismic theoretical displacement field of the Ning’er earthquake fault, calculated based on the inverted fault parameters, are consistent with those of the observed isoseismals.