摘要
本文根据非线性动力学观点,从地震活动特征和岩石模拟实验两个方面研究了大地震孕育和发生的动力学过程。初步结果得到:地震活动特征具有统计自相似性,且其时、空分布特征比较复杂,具有非整分维,分别类似于康托尔集合或一维连续统⊕康托尔集合。而且我们发现在主震前,地震活动在相空间呈现一种低维浑沌状态。它们都有一个维数比较低的奇怪吸引子,表现为一种浑沌序。主震后,其地震活动表现为一种维数很高且无饱和值的类随机噪声。岩石失稳破裂前,其声发射活动频度的分布也表现为一种浑沌态,其关联维数值为3.1,高于地震。在信息维研究中,首次发现在大地震发生前和岩石失稳破裂前,均有一个明显的降维过程,表现为一种有序态。随后不确定性增大,其维数值增高,直至大震发生和岩石失稳。同时发现标度性发生变化。首次得到大震前或岩石失稳前无标度区急剧变窄,表现出强烈的临界不稳定性。其它期间包括主震后均不存在上述现象。显然这对探索短期预报具有重要意义。
This paper,based on the point of view of nonlinear dynamics,studies the dynamic processes of seismogeny and occurrence of large earthquakes from the two aspects of seismicity characteristics and rock experiment.Primary results got are that seismicity chara- cteristics possesses self-similarity in statistics,is more complex in features of temporal -spatial distribution,has non-integral fractal dimension and is respectively simular to Cantor set or one-dimensional continuum⊕Cantor set.But we have found that seismic activities show a low dimensional chaotic state in phase space before the mainshock;and these seismic activities all have a strange attractor of lower dimension and appear as a chaotic order. after the mainshock the seismicity displays a kind of random noise with very high dimension and no saturation value. Before rock failure fracture,the frequency distribution of acoustic emission activity also appears in a chaotic state and its correlation dimension value is 3.1,which is above that of the earthquake.In studies of information dimension,it has been found for the first time that there always exists an evident process of decreasing dimension,with an orderly state,before the occurrence of a large earthquake and rock failure fracture.And then,indeterminacy increases and so does the dimension value until the occurrence of the large earthquake or rock failure fracture.At the same time the scaling changes,and it has been found for the first time that before the occurrence of a large earthquake or rock failure,the non-scaling area abruptly narrows,showing extremely critical instability.The phenomena mentioned above do not appear at other periods,including the post-mainshock period.Obviously this is significant in the exploration of the laws for short-period earthqua- ke prediction.
出处
《国际地震动态》
1992年第4期1-6,共6页
Recent Developments in World Seismology
