根据截断的G-R模型计算东北地震区震级上限

震级上限是指一个地区可能发生地震的最大震级,其概率意义为发生超过该震级地震的概率几乎为0.在有些地区,由于对其内部的地震构造研究和认识存有局限性,很难根据构造或者地质学的原则来确定震级上限.因此,根据数学模型,采用统计手段,使用地震活动性资料来计算震级上限的估计值是一种可行的方法.本文根据截断的G-R关系模型,采用最大似然计算方法,使用东北地震区的地震目录,计算了东北地震区震级上限,结果表明东北地震区的震级上限应为Mu=7.5左右.计算中我们考虑了不同震级的转换、震级误差的修正以及计算方法的影响.最终结果表明,不论采用何种方案进行计算,东北地震区的震级上限值均始终保持在7.5左右,这说明我们采用本文中方法计算得到的东北地震区的震级上限值是合理可信的,同时也说明在以往的研究中对东北地震区震级上限的估计大都是偏小的.

Calculation of upper limit earthquake magnitude for Northeast seismic region of China based on truncated G-R model

The upper bound earthquake magnitude(Mu) means the largest possible magnitude of earthquakes occurring in the seismic source zone.The expected probability of the earthquake with a magnitude exceeding the upper bound tends to zero.In some regions,because of the limited knowledge of seismic structures and the cause of earthquake formation,we can hardly estimate the value of the upper bound earthquake magnitude according to tectonics and geology.It is feasible to use statistical method and seismic catalog to calculate the estimated value of the upper bound earthquake magnitude according to a mathematical model.In this study,we estimate the upper bound earthquake magnitude from seismic catalog in Northeast seismic region according to the truncated G-R relationship.The result shows that the upper bound earthquake magnitude in Northeast seismic region Mu is about 7.5.We have considered the influence from the transformation between different magnitude scales,the correction for magnitude errors and the different mathematical methods used in calculation,the final results all show that the Mu always maintains a constant value which is about 7.5.Our study indicates that the estimated value of upper bound earthquake magnitude Mu=7.5 is reasonable,and the estimated value of upper bound earthquake magnitude Mu=7.0 in past studies is too small.