| Earthquake forecasting is an important problem demanding prompt solutions, which is also a universal scientific problem maybe solved by exploring for a long time. The relationship between crustal deformation and earthquake should be studied not only through the directional distribution of crustal deformation but also the dynamic changes of deformation time course. We focus on Yanshan--bohai seismic zone in this paper, in which there are plentiful crustal deformation observations. Firstly, we studied the relative motion and mode of texturing, strain accumulation and its sub-features of Yanshan--Bohai Zone by processing the GPS velocity data. Secondly, we got the tidal LURR dynamic changes with time by processing continuous tilt observations based on the knowledge of the strain accumulation of Yanshan--Bohai Zone. Furthermore, the tidal Load and unload response ratio anomalies before Wen'an Ms5.1 earthquake was discussed, and its seismic predictive efficiency was evaluated.In this part, we first studied the suitability of rotation in the rigid block model (RRM),rotation in the entire block and homogeneous strain model (REHSM) and rotation in the entire block and linear strain model (RELSM) for North China by processing 1999~2001,2001～2004,2004～2007 GPS velocity field. After that, we used the GPS velocity data whose noise was removed by least squares collocation method as the input of REHSM to analyze the motion and deformation of Yanshan--Bohai Zone and then calculated the relative movement of different parts in different periods.In the second part, we studied the variation and evolution of the LURR of tidal factors of O1 and M2 waves which belongs to diurnal waves and semidiurnal waves respectively through processing tilt tidal observations of four stations in North China based on Load and Unload response ratio theory. In brief, we got some rudimental result by analyzing large and small scale crustal deformation respectively.1. We find that the rotation in the entire block and homogeneous strain model (REHSM) is the most suitable model for North China judged by the dispersion of velocity residual.2. During 1999~2001 period, Yinshan Zone was a left-lateral extension strike slip belt with the slip rate less than 1.0mm/a and extension rate less than 1.35mm/a. In 2001~2004 and 2004~2007 period, Yinshan Zone was also left-lateral strike slip with the rate of 0.04mm/a~1.59mm/a, but the extensional feature was not very obvious. Furthermore, its motion became obviously slow in 2001~2004. The deformation character of Zhangjiakou--Bohai Zone was left lateral strike slip in the three periods with amplitude of 0.7mm/a~1.55mm/a. Though its deformation state varied from time to time, the rate was always less than 1.0mm/a. In conclusion, it squeezed in the north and west of Yanshan--Bohai Zone while tensed in the southern and eastern part.3. Though the tendency of YO 1 and YM 2 fits well, the amplitude of YO 1is larger than YM 2, which means that O1 wave is more sensitive to crustal deformation than M2 wave.4. After we analyzed two kind of tilt observations of four stations in North China, we find that the time and amplitude of earthquake precursor is related to the distance between station and epicenter, instrument performance,working atmosphere and the direction. And the distance is shorter, the time is earlier and duration is longer. In brief, not only the efficiency of YO 1, but also of YM 2 are significant before Wen'an earthquake.This study is just desk study of strain tidal response ratio, which is to provide reference to further studies. |
PDF Full Text Request