震级频度与古登堡-里克特关系式偏离的前兆意义

Precursory significance of the deviation of the magnitude-frequency from the G-R relation

地震震级频度的古登堡-里克特关系式(简称G-R关系式)一直是许多地震学问题研究的重要前提之一,然而实际分布常常与这一关系式有一定的偏离。文中利用已有的对含有凹凸体、挤压雁列破裂及Ⅲ型剪切破裂等三种类型的岩石实验结果,对接收到的声发射事件序列分别进行了分段地震震级频度的G-R关系式拟合,重点考察了每一时间窗内表征实际地震震级频度与这一关系式偏离程度的线性拟合系数r值的变化。研究结果表明,含有凹凸体、挤压雁列破裂的岩石声发射序列在加压-破裂过程中,分段扫描分别计算得出的r值在标本失稳前出现数字下降的现象,表明临近岩石失稳,实际地震震级频度与G-R关系式偏离程度有加大的趋势;而含Ⅲ型剪切破裂的岩石在标本失稳前,声发射序列r值数字下降的现象不明显。部分实际震例也表明,在一些中强地震前也存在着这种偏离。研究结果可能对利用区域地震活动资料探求部分类型的中强地震前可能存在的前兆信息具有一定的参考意义。

The G R relation between the earthquake magnitude and frequency has been an important premise in seismological study, but its actual distribution often deviates from its theoretic result. Based on the experimental results of the three types of rock samples containing macro asperity, compressional en-echelon fracture and model-Ⅲ shear fracture, this paper has newly fitted the G-R relation in the sequences of the rock sample＇s acoustic emission by the different scales of magnitude and frequency, and emphatically reviewed the change of the linear fitting coefficient value , which figures the actual deviation degree of earthquake magnitude and frequency from the G R relation within every time window. The results show that the value that counted separately is becomes lower before the instability occurred in the process of deformation of the three types of rock samples, indicating that the deviation degree of earthquake magnitude and frequency from the G R relation is increases. Some earthquakes cases tell us that the deviation degree exactly exists before the occurrence of moderate earthquakes. The results provide certain useful reference in searching the precursors before the occurrence of moderately strong earthquakes by using the data of the regional seismic activity.