Application And Research Of The New IASPEI Magnitude Scales With The Broad-Band Digital Seismic Records

Magnitude is one of the basic parameters to measure the size of an earthquake.Different seismological institutions in the world have different magnitude measurements.The issue of the magnitude measurements based on digital seismic instruments has aroused great attention of the IASPEI and many countries.The International Association of Seismology and Physics of Earth's Interior(IASPEI) founded the Working Group on Magnitude in 2001 to study magnitude measurement with broad-band digital seismic data.With several years' efforts,the WG has done a lot of basic research and accumulated a large amount of practical observational data.A new magnitude scale and measurement was proposed by the WG in 2003 and this magnitude scale and measurement was approved formally by the IASPEI Commission on Seismological Observation and Interpretation(CoSOI) on the IASPEI 33rd General Assembly held in Santiago,Chile in October 2005.The new IASPEI body wave magnitude scales are short-period body wave magnitude m_b and broadband body wave magnitude m_B(BB),and the surface wave magnitude scales are 20 s surface wave magnitude m_S(20) and broadband surface wave magnitude m_S(BB).The proposal of the new magnitude scales is mainly based on two fundamental considerations:one is the continuity of the magnitude measurements,and the other is the full use of the characteristics of the broadband digital seismic records.In order to promote the new IASPEI magnitude scales and ensure the continuity and compatibility of the use of the magnitudes,the relationship between the new IASPEI magnitudes and the traditional scales should be studied.The fact that the China Seismograph Network(CSN) constructed digital seismic stations during the "the 9th Five-Year Plan" and accumulated rich waveform data has laid a solid foundation of studying the relationship between the new IASPEI magnitude scales and the CSN traditional scales.We will not only recommend a worldwide standard of magnitude determination in this study but also provide important fundamental data for making the observatory technical specifications for digital seismic stations/networks in China;so that the new magnitude scales can be applied to the CSN routine work and the magnitude measurements can be in line with international practices.Applying the new recommended body and surface wave magnitude scales,selecting the data from the 564 representative earthquakes between 2001 and 1007,whose distances are less than 100°,recorded by the 48 stations of the China National Digital Seismograph Network,determined the short-period body wave magnitude m_b(i),broad-band body wave magnitude m_B(i),broad-band surface wave magnitude M_S(BB),and 20 s surface wave magnitude M_S(20) on the new scales with the SHM.Meanwhile,we have also determined the short-period body wave magnitude m_b,the middle-/long-period body wave magnitude m_B,the 763 seismometer surface wave magnitude M_S7,and long-period surface wave magnitude M_S on the Chinese traditional scales with the same data.The regression analysis of the magnitudes among the different Chinese traditional scales, among the different new IASPEI scales and between the traditional and IASPEI scales of the same types are respectively made with linear regression and orthogonal regression.Moreover,the regression relationships of the different magnitudes are given and the results of the regression analysis are explained in detail.The new IASPEI magnitude scales will promote the uniformity of the magnitude measurements among the seismological institutions all over the world.The radiant energy of the moderate and large earthquakes can be reflected by the new short-period body wave magnitude m_b(i) more accurately;the magnitude of the earthquake can be determined more quickly with the new broad-band body and surface wave magnitudes m_B(i) and M_S(BB);There isn't system error between M_S(20) on the new scale and Chinese traditional M_ST.Therefore,CSN may adopt the new IASPEI magnitude scales in advance,so that the CSN data can gradually keep up with the word development.The first chapter of this dissertation gives an overview of the development and current status of the magnitude research in China and abroad,and from this,leads to the study background and purpose of the dissertation.The formulae and measurements of the new IASPEI magnitude scales and the traditional ones in China are introduced and the differences between the two are summarized in Chapter 2.Chapter 3 makes an introduction to the CSN's development and the used data and waveform analysis software in this dissertation.Using the general linear regression and the orthogonal regression,the computing results of the magnitudes in Chinese traditional and new IASPEI scales were compared in Chapter 4.Moreover,the regression analysis relational expressions are given and the relationship of the different magnitudes is analyzed in detail in this chapter.The last chapter makes a summary and conclusion of the dissertation and points out some issues for further discussion.