摘要
采用线性回归和正交回归方法,利用中国地震台网1983—2004年的观测资料,对中国地震局地球物理研究所测定的地方性震级ML、面波震级MS与MS7、长周期体波震级mB、短周期体波震级mb进行对比,给出了它们之间的经验关系式.研究结果表明:①由于不同的震级标度反映了地震波在不同周期范围内辐射地震波能量的大小,因此对于不同大小的地震,使用不同的震级标度更能客观地描述地震的大小.当震中距小于1000km时,用地方性震级ML可以较好地测定近震的震级.当地震的震级M<4.5时,各种震级标度之间相差不大.当4.5<M<6.0时,mB>MS,MS标度低估了较小地震的震级,因此用mB可以较好地测定较小地震的震级.当M>6.0时,MS>mB>mb,mB与mb标度均低估了较大地震的震级,用MS可以较好地测定出较大地震(6.0<M<8.5)的震级.当M>8.5时,MS出现饱和现象,不能正确地反映大地震的大小;②在我国境内,当震中距<1000km时,ML与区域面波震级MS基本一致,在实际应用中无需对它们进行震级的换算;③虽然MS与MS7同为面波震级,但由于所使用的仪器和计算公式不同,MS比MS7系统地偏高0.2～0.3级;④对于长周期体波震级mB和短周期体波震级mb,虽然使用的计算公式相同,但由于使用的地震波周期不同,对于mB=4.0左右的地震,mB与mb几乎相等,而对于mB≥4.5的地震,则mB>mb.
By linear regression and orthogonal regression methods, comparisons are made between different magnitudes （local magnitude ML, surface wave magnitudes Ms and Ms7 , long-period body wave magnitude mB and short-period body wave magnitude mb） determined by Institute of Geophysics, China Earthquake Administration, on the basis of observation data collected by China Seismograph Network between 1983 and 2004. Empirical relations between different magnitudes have been obtained. The result shows that： ① as different magnitude scales reflect radiated energy by seismic waves within different periods, earthquake magnitudes can be described more objectively by using different scales for earthquakes of different magnitudes. When the epicentral distance is less than 1 000 kin, local magnitude ML can be a preferable scale; In case M〈4.5, there is little difference between the magnitude scales; In case 4.5〈M〈6.0, mB〉Ms, i.e. Ms underestimates mag nitudes of such events, therefore, mb can be a better choice; In case M〉6.0, Ms〉mB〉 mb, both mB and mb underestimate the magnitudes, so Ms is a preferable scale for determining magnitudes of such events （6.0〈M〈8.5）; In case M〉8.5, a saturation phenomenon appears in Ms, which cannot give an accurate reflection of the magnitudes of such large events; ② In China, when the epicentral distance is less than 1 000 kin, there is almost no difference between ML and Ms, and thus there is no need to convert between the two magnitudes in practice;③ Although Ms and Ms7 are both surface wave magnitudes, Ms is in general greater than Ms7 by 0.2-0.3 magnitude, because different instruments and calculation formulae are used; ④ mb is almost equal to mb for earthquakes around mB4.0, but mB is larger than mb for those of mB≥4. 5, because the periods of seismic waves used for measuring mB and mb are different though the calculation formulae are the same.
出处
《地震学报》
CSCD
北大核心
2007年第5期467-476,共10页
Acta Seismologica Sinica
基金
科技部地震行业专项资助.
关键词
地方性震级
面波震级
体波震级
local earthquake magnitude
surface wave magnitude
body wave magnitude
