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本文研究现行测定近震震级公式M_L=logAμ+R(△)对同一个地震而言,各地震台站测定的震级大不一致的原因入手,从地震波的衰减规律探索测定近震震级方法。本文认为主要有四个原因造成近震震级测定结果不一致。(一)震级起算函数R(△)存在明显的地区性差异;(二)地震波传播过程中存在扩散作用的影响;(三)震源位错方式对辐射地震波能量和能谱具有方向性差异;(四)震源深度影响。这四方面的问题,用简单的台基校正是解决不好的。因此,首先必须建立近震震级的起算函数并重新测定出适合本地区情况的震级起算函数R(D)值。地球介质本身的性质在各个地区是不同的。它的非完全弹性、非均匀性以及地震波本身的传播还有随距离增加而振幅随之减小的扩散作用,使地震波的振幅实际按: A_μ=A_u·D~(-N)·e~(-a·D) (1)的规律衰减。根据李克特(C.F.Richter)震级公式的原始意义,对(1)右边取对数、移项整理得: M_L=logAμ+NlogD+a·Dloge (2)并设M_l=logA_u,R(D)=NlogD+a·Dloge取N=1则 M_L=LogAμ+R(D) (3)式中R(D)为近震震级起算函数。选用山东省台网记录的11个典型地震,102个台组的数据统计求得衰减系数a=0.011524,因此可根据R(D)=logD+0.005005D计算本地区的任何距离上的R(D)值。在地动位移计算方法上采取三维矢量合成,使共解决能量、能谱辐射的方向性影响和震源深度影响。
In this paper, we study the reason why the measured magnitude of near-epicenter magnitude M_L = logAμ + R (△) is very different for all the seismic stations in the present study, and explore the method of determining the magnitude of near-earthquakes based on the decay law of seismic waves. This paper argues that there are mainly four reasons for the inconsistency of the results of near-earthquakes. (1) There is obvious regional difference in the R (△) initial magnitude function of the magnitude; (2) The influence of the diffusion exists in the propagation of the seismic wave; (3) The dislocation mode of the source has a directional difference to the energy and energy spectrum of the radiation seismic wave; D) Focal depth effect. These four aspects of the problem, with a simple platform-based correction is not good solution. Therefore, we must first establish the initial function of the near-Earthquake magnitude and re-determine the R (D) value of the magnitude that fits the local situation. The nature of the Earth’s medium itself is different in all regions. Its imperfect elasticity, inhomogeneity and propagation of the seismic wave itself also have the effect of decreasing the amplitude with the increase of the distance, so that the amplitude of the seismic wave actually follows: A_μ = A_u · D ~ (-N) · e ~ ( -a · D) The law of (1) decay. According to the original meaning of CFRichter’s magnitude formula, take the logarithm of the right side of (1), the shift is: M_L = logAμ + NlogD + a · Dloge (2) and let M_l = logA_u, R = NlogD + a · Dloge take N = 1 then M_L = LogAμ + R (D) (3) where R (D) is the starting function of the near-Earthquake magnitude. According to R (D) = logD + 0.005005D, R (D) at any distance in this area can be calculated by using the data of 102 stations recorded by 11 typical earthquakes recorded by Shandong Province Network as attenuation coefficient a = 0.011524. )value. Three-dimensional vector synthesis is used to calculate the displacement of ground motion, which can solve the directivity influence of energy and energy spectrum radiation and depth of source effect.