中国东南地区塑性流动波与地震迁移(Ⅰ)

PLASTIC-FLOW WAVES AND EARTHQUAKE MIGRATION IN SOUTHEAST CHINA (Ⅰ)

根据岩石圈塑性流动网络与塑性流动波 (网络波 )的观点 ,在采用和改进以往对于亚洲中东部其它地区网络波研究方法的基础上 ,通过地震活动沿塑性流动网带的迁移、速度场及边界起波期等研究 ,绘制了中国东南地区网络波走时等值线图和波峰带分布图 ,初步展示了网络波控制下的地震能量背景 ,为进一步的研究及该地区地震能量背景的物理预测提供了依据。

It is known from the paper (Ⅰ) that earthquakes, controlled by the plastic flow waves, or called network waves, occur mainly in the wave crest belts in which energy concentrates relatively. Based on the distribution of earthquake released energy (Fig.1), the distribution of energy along the direction normal to wave crest belts (Fig.2) and the attenuation of energy with propagation distance (Fig.3) are analyzed further in this paper. In addition, the distribution of earthquake occurrence probabilities is estimated in consideration of its relation to the seismic background energy. As a result, the distribution map of earthquake occurrence probabilities associated with the seismic energy background in the southeastern China region (Fig.4) is given as one of the supports for earthquake prediction. The distribution of relative values of earthquake released energy along the direction normal to wave crest belt, p , is approximately shown as the Gaussian distribution (eq.1 and Fig.2), where Δ T=T-T av , T av is the average travel time for the wave crest belt, corresponding to the position of the belt's mid line, S is the standard error in travel time. The total energy for each wave crest belt, Σ E , attenuates as an exponential function of its travel time (Fig.3) and the tendency of the decrease in earthquake magnitude with increasing propagation distance can be expressed by the attenuation coefficient α . The distribution maps of wave crest belts given in the paper (Ⅰ) and the seismic energy background map expressed by earthquake occurrence probabilities given in this paper show the propagation characteristics of the network waves originated from the Taiwan driving boundary in the southeastern China region. The former can be used as a basis for preliminarily determining the seismic energy background zones and the latter is one of the bases for the quantitative prediction of seismic risk regions. Both of them will be examined in the practice of earthquake prediction and revised progressively to approach the actual situation of the propagation of plastic flow waves. As the 'cloud chart' used for weather forecasting, showing the distribution of water necessary for precipitation, the seismic energy background map (Fig.4) provides an 'energy chart' for earthquake prediction, showing the distribution of energy necessary for earthquakes. It is noteworthy that the seismic background 'energy chart' can be established and used for earthquake prediction on the basis of the ideas of plastic flow network and plastic flow waves through other approaches, such as the inversions of ground deformation or other geophysical fields, in addition to the time space distribution of earthquakes stated in this paper. It may be more effective to synthesize the results obtained from different approaches for improving the reliability of the seismic 'energy map'.