中国大陆地区的均一震级系统
HOMOGENEOUS MAGNITUDE SYSTEM OF THE MAINLAND CHINA
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摘要: 用 SK 地震仪台网的资料,用联合确定地震震级、量规函数和台基校正值的方法,做出了中国大陆地区的均一震级系统,得到了 PZ、PH、SH、SV 四个震相从2.5——100新的量规函数,以及我国21个基准台的台基校正值.用这四个量规函数加上台基校正,求得的单台震级的标准误差为0.21——0.23级.6级左右的地震一般都有16个以上台记录到,这时求得的台网平均震级的误差可在0.05级左右.由于体波震级强烈地依赖于仪器类型,所以,我们求得的体波震级 msk与 mb 或 mB 有系统差.我们采取了使 msk与 Ms 接近的原则.提出了位移谱震级的概念:认为按某一震源参考球的平均值,具有相同强度的 P 波(或 S波)位移谱的地震,则震级相等.这种震级标度有以下优点:(1)它是绝对力学标度,可以把世界上各台网的震级统一起来;(2)物理意义明确,能反映地震大小.对任何大小地震都有定义,无饱和问题,对慢地震也有定义;(3)能和以前使用的震级衔接起来;(4)对位移计地震仪来说,测量方便,误差小.Abstract: Homogeneous magnitude system of the mainland China has been made from the data of SK instrumental network, using the method that together obtain earthquake magnitude, calibration function and correction of the site condition. Four new calibration functions have been obtained for P-wave PZ, PⅡ, and S-wave SH, SV from the distance of 2.5 to 100 degree. 21 corrections of the site condition are also obtained. The standard error of single station measurement of earthquake magnitude is about 0.21-0.23, utilizing the new calibration function and the corrections of site condition. The earthquake the magnitude of which is equal to or greater than 6.0 can be usually recorded by 16 stations. In this case, the standard error of average magnitude over the network is about 0.05. The body wave magnitude mSK, from SK instrumental measurement has a systematic difference to mb and mB, because mSK, mb and mB depend on instrument of measurement strongly. The principle of making mSK close to Ms is adopted.We have a suggestion of magnitude of displacement spectrum: the earthquake will be equal to each other at one frequency when their average displacement spectrum over on some focal reference sphere has the same value for P-wave (or S-wave). This magnitude scale has following advantage: 1. The magnitude of network on different region of all over world can be unified in view of it being absolute mechanical scale. 2. It has obvious meaning in physics. It can represent the size of earthquake and can be defined for any size and slow earthquakes as well as has no saturation trouble. 3. It can link up the current magnitude scale. 4. The measurement is easy and has less error for the displacement instrumental record.