地方震尾波震级的初步研究

PRELIMINARY RESEARCH OF LOCAL EARTHQUAKE CODA MAGNITUDE

摘要:

地方震尾波由地壳横向不均匀性而产生的反向散射波组成。从这一观点出发,根据尾波随掠过时间的衰减特性,结合地震矩对数和地方震里克特地震级的线性关系,导出利用任一掠过时间的震尾来计算的尾波震级Mc公式。它的简化形式可以和持续时间震级的表达式近似一致。尾波震级可作为持续时间震级的一种广义形式,它是直接从震源地震矩导出的震级标度,从而为解释持续时间震级物理基础提供了可能的途径。
应用于丹江地震台的资料,得到丹江口及邻区的尾波品质因子和介质函数以及地震矩对数和震级的期望关系,同时得到实用于该台的持续时间震级和简化尾波震级公式。

Abstract:

The seismic coda wave of local earthquakes are composed of back scattering waves owing to numerous randomly distributed heterogeneities in the earth's crust. On this view, in consideration of linear relation between the seismic moment and the local Richter magnitude, a formula of the coda magnitude M_c is derived by using seismic coda of any lapse time, measured from the earthquake origin time. Its simplified form may be cinsistent with the relation of the duration magnitude M approximately. We may regard M_c that describes the size of the seismic moment of the focus as a generalized form of M. Hence a possible way is proposed for the explanation of the physical background for the duration magnitude.
In Danjiangkou and its nearby regions a quality factor of coda wave, a function of the medium and a expectancy relation between the seismic moment and the local Richter magnitude are attained by applying to the data from the Danjiang Station. At the same time, we found a formula of the duration magnitude and a simplified formula of the coda magniude for the station.