| The previous researches on the seismogenic process emphasized particularly on single earthquake source model and theory, and studied the phenomena and mechanisms of long term medium term and short-term earthquake preparation process according to its temporal and spatial dynamic evolvement of stress field and strain field in earthquake source and its neighboring area. However, the facts of seismic activities show that strong earthquakes aren't isolated each other, they have consanguineous relationship. Some of strong group earthquakes are the outcome of the same seismogenic process. Scientists have put emphasis on interaction of strong earthquakes since 1990's. The interaction and influence of earthquakes each other is one of an important factor, which is also of the complexity of seismic activities.In the article, from phenomenon to theory, we have studied the characteristics of strong group seismogenic earthquakes and group activities and tried setting up 3D finite element model and studied the mechanism of strong earthquakes group activities, particularly, aiming at Sichuan-Yunnan special region, applying the latest research result of geologic structure and deep physical geography. It is only the original intention to set up a theoretical basal platform for earthquake analysis and prediction and to search for some ways for physical prediction.First, let us take the history record of activities of the earthquakes on the mainland as the sample of statistics to analyze the distribution characteristics of the mainland earthquakes in both time and space. It shows that no matter we take the mainland as a whole to study, or take the mainland as two sections(the east and the west), even take the activities of the earthquakes in a certain region to study, the mainland activities occur in cluster in both time and space. That is to say there is a clear objectivity in the characteristic of the activities of the strong mainland earthquakes-group activity.Then, a simple way that is At-value scanning method is adopted to make a semi-quantitative research on the correlative characteristics of inter-earthquakes and to calculate the change of the strain release before and after region strong earthquakes occurred. Through the large range responding condition described by spatial scanning image, we have analyzed the seismic activities before and after strong earthquakes in north of China, southwest region and northwest region. Analysis of a great many data shows that some strong earthquake will arouse seismogenic zone loading and bring the increase of stress, accelerate accumulation of nonlinear strain of medium. It will make the earthquake source rupture of high stress status in unsteadiness in advance, which resulting the proceeding earthquake occur in advance. So strong earthquakes is associated in time and space.Then, we have made a further research for Sichuan-Yunan district. Based on the Okata theory of stress triggering, we make a systemic analysis on the triggering each other of strong earthquakes and group activities of earthquake. The statistical result shows that about 50 percent of earthquakes occurred in the positive area of coulomb rupture stress of the preceding earthquake. 30 percent of earthquake occurs in the negative area and20 percent of them occurred in the boundary area.Based on above research, the 3D finite element research on mathematic modeling research has been carried out for group activities and interaction of earthquakes. First, We try setting up 2D finite element model of stress evolvement and seismic activities for tectonic blocks of Qinghai-Tibet Platean. Study the relationship of stress evolvement, adjustment and group seismogenic activities of strong earthquakes and make a preliminary modeling the interaction characteristic between strong earthquakes in tectonic blocks of Qinghai-Tibet Platean.The research shows that we can simulate and calculate the function of adjustment and influence of stress by the way of finite element, and determine the increasi...
|
PDF Full Text Request