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一、问题的提出震级是地震最基本的参数之一,它的精确测定对于地震研究和预报无疑都很重要。目前甘肃地区测定大量中小地震震级的方法,都是利用S波两个水平分向最大地动位移的平均值Aμ,由公式M_L=lgAμ+R(Δ)+S (1)求得,然后取多台平均,再由 M_L=1.13M_L-1.08 (2)换算为面波震级;仅少数较大的地震用中长周期仪器资料直接求取面波震级Ms。(1)式中R(Δ)为震级起算函数,它反映了地震波振幅随震中距的衰减特性,在震级测定中则是一个距离改正值。多年来,甘肃地区使用的起算函数R(Δ)是根据全国资料得出的大范围内的平均结果。
First, the issue of the proposed magnitude is one of the most basic parameters of the earthquake, its precise determination of undoubtedly important for earthquake research and prediction. At present, the method of determining the magnitude of a large number of medium-sized earthquakes in Gansu is to use the average value Aμ of the maximum ground motion displacement of the two horizontal directions of the S-wave and obtain the formula M_L = lgAμ + R (Δ) + S (1) And then averaged by M_L = 1.13M_L-1.08 (2), converted into surface wave magnitude. Only a few large earthquakes directly obtain surface wave magnitude Ms. using medium-long period instrument data. (1) Where R (Δ) is the starting function of magnitude, which reflects the decay characteristics of seismic amplitude with epicenter distance, and is a distance correction value in magnitude determination. Over the years, the starting function R (Δ) used in Gansu has been a large-scale averaging based on national data.