不同标度震级关系和台基影响问题探讨
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摘要
利用近年中国数字地震台网观测报告中的中国及邻区地震目录资料,取能够同时计算面波震级MS和近震震级ML的地震,拟合出2种震级之间的关系,发现与过去使用30余年的换算公式存在系统差别。考虑现代化地震数字观测系统有动态范围大、频带宽、台站多、覆盖区域广、测定精度高的特点,由此拟合的关系应当更可靠。考虑不同误差因素统计面波震级MS和近震震级ML的关系表明,2种震级之间换算和不换算的差别并不大,因此建议MS和ML震级之间不换算为宜。分析地震台站的场地响应发现:一些基岩台的放大因子在1附近,场地响应不随频率变化;处于沉积土层的台站,放大因子在低频段大于1,高频段小于1;还有一些台站在某个频段范围大于1,或者小于1。另外,沉积土层台站的单台震级和台网平均震级差也随周期增大,呈现由负到正的增长趋势。看来并不存在固定的台站校正系数,因此不能把台站校正作为提高震级测定精度的方法。
Based on the earthquake catalog reported by the Chinese digital seismic network in recent years,we select the earthquakes with both of surface wave magnitude and local magnitude and fitting them into the relation between two magnitudes. The systematic difference is found from the formula that has been used for 30 years. Because of large dynamic range and wide frequency range of current digital observation system,in addition to larger number of stations and earthquakes used than before,the relation obtained seems more reliable. Our calculation shows that there is no significant difference before and after magnitude conversion,the magnitude conversion is suggested to be given up. The site response of a station consists of the amplification at different frequencies. The amplifications are about 1 and change little with frequency at stations located on basement rock,the amplifications are greater than 1 on low frequency range and less than 1 on high frequency range at stations located on sediment layer,the difference between magnitude from single station located on sediment layer and the average magnitude from whole network increases from negative to positive with period. It seems that there is no fixed station correction factor and station correction method does not work for improvement of magnitude accuracy.
Based on the earthquake catalog reported by the Chinese digital seismic network in recent years,we select the earthquakes with both of surface wave magnitude and local magnitude and fitting them into the relation between two magnitudes. The systematic difference is found from the formula that has been used for 30 years. Because of large dynamic range and wide frequency range of current digital observation system,in addition to larger number of stations and earthquakes used than before,the relation obtained seems more reliable. Our calculation shows that there is no significant difference before and after magnitude conversion,the magnitude conversion is suggested to be given up. The site response of a station consists of the amplification at different frequencies. The amplifications are about 1 and change little with frequency at stations located on basement rock,the amplifications are greater than 1 on low frequency range and less than 1 on high frequency range at stations located on sediment layer,the difference between magnitude from single station located on sediment layer and the average magnitude from whole network increases from negative to positive with period. It seems that there is no fixed station correction factor and station correction method does not work for improvement of magnitude accuracy.
引文
卞真付、姚兰予、庞群英,2005,利用井下数字地震记录反演非弹性衰减系数震源参数和场地响应,西北地震学报,27(S1),60～66。
陈运泰、吴忠良、王培德等,2000,数字地震学,1～7,北京:地震出版社。
国家地震局,1990,地震台站观测规范,北京:地震出版社。
高立新、郑斯华、丁风和,2005,内蒙古中西部地区震源参数和场地响应反演,西北地震学报,27(2),109～114。
何永年,1999,《地震震级的规定》宣贯教材,1～5,北京:中国标准出版社。
黄玉龙、郑斯华、刘杰等,2003,广东地区地震动衰减和场地响应的研究,地球物理学报,46(1),54～61。
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兰从欣、刘杰、郑斯华等,2005,北京地区中小地震震源参数反演,地震学报,27(5),498～507。
刘杰、郑斯华、黄玉龙,2003,利用遗传算法反演非弹性衰减系数、震源参数和场地响应,地震学报,25(2),211～218。
刘瑞丰,2003,地震参数,7～15,北京:地震出版社。
沈小七、刘杰、陈宇卫等,2005,安徽地区地震波衰减、场地响应及震源新参数的测定,地震地磁观测与研究,26(3),1～10。
王勤彩、高景春、郑斯华等,2004,华北中北部地区震源参数和场地响应的联合反演,中国地震,20(2),187～196。
吴忠良、张天中,2003,地震参数,1～2,北京:地震出版社。
许绍燮等,1999,地震震级的规定GB17740-1999,北京:中国标准出版社。
赵翠萍、张智强、夏爱国等,2004,利用数字地震波资料研究新疆天山中东段地区的介质衰减特征,防灾减灾工程学报,25(3):300～305。
中国科学院地球物理所,1976,地震学基础,142,北京:科学出版社。
中国科学院地球物理所,1977,近震分析,51～52,北京:地震出版社。
中国地震局地球物理所,2001,中国数字地震台网观测报告(2000),北京:地震出版社。
中国地震局地球物理所,2002,中国数字地震台网观测报告(2001),北京:地震出版社。
中国地震局地球物理所,2003,中国数字地震台网观测报告(2002),北京:地震出版社。
中国地震局地球物理所,2004,中国数字地震台网观测报告(2003),北京:地震出版社。
Chinnery M.A.,North,R.G.,l975,The frequency of verylarge earthqualle,Science,190,197～1198.
Gutenberg,B.,1945,Amplitude of surface waves and magnitudes of shallowearthquakes,Bull.Seism.Soc.Amer.,35,57～59。
Kanamori,H.,l983,Magnitude scale and quantificaion of earthquthes,Tectonophysics,93,185～199.
陈运泰、吴忠良、王培德等,2000,数字地震学,1～7,北京:地震出版社。
国家地震局,1990,地震台站观测规范,北京:地震出版社。
高立新、郑斯华、丁风和,2005,内蒙古中西部地区震源参数和场地响应反演,西北地震学报,27(2),109～114。
何永年,1999,《地震震级的规定》宣贯教材,1～5,北京:中国标准出版社。
黄玉龙、郑斯华、刘杰等,2003,广东地区地震动衰减和场地响应的研究,地球物理学报,46(1),54～61。
李祖宁、周峥嵘、林树等,2005,利用数字地震台网资料联合反演福建地区Q值、场地响应和震源参数,地震地质,27(3),437～445。
兰从欣、刘杰、郑斯华等,2005,北京地区中小地震震源参数反演,地震学报,27(5),498～507。
刘杰、郑斯华、黄玉龙,2003,利用遗传算法反演非弹性衰减系数、震源参数和场地响应,地震学报,25(2),211～218。
刘瑞丰,2003,地震参数,7～15,北京:地震出版社。
沈小七、刘杰、陈宇卫等,2005,安徽地区地震波衰减、场地响应及震源新参数的测定,地震地磁观测与研究,26(3),1～10。
王勤彩、高景春、郑斯华等,2004,华北中北部地区震源参数和场地响应的联合反演,中国地震,20(2),187～196。
吴忠良、张天中,2003,地震参数,1～2,北京:地震出版社。
许绍燮等,1999,地震震级的规定GB17740-1999,北京:中国标准出版社。
赵翠萍、张智强、夏爱国等,2004,利用数字地震波资料研究新疆天山中东段地区的介质衰减特征,防灾减灾工程学报,25(3):300～305。
中国科学院地球物理所,1976,地震学基础,142,北京:科学出版社。
中国科学院地球物理所,1977,近震分析,51～52,北京:地震出版社。
中国地震局地球物理所,2001,中国数字地震台网观测报告(2000),北京:地震出版社。
中国地震局地球物理所,2002,中国数字地震台网观测报告(2001),北京:地震出版社。
中国地震局地球物理所,2003,中国数字地震台网观测报告(2002),北京:地震出版社。
中国地震局地球物理所,2004,中国数字地震台网观测报告(2003),北京:地震出版社。
Chinnery M.A.,North,R.G.,l975,The frequency of verylarge earthqualle,Science,190,197～1198.
Gutenberg,B.,1945,Amplitude of surface waves and magnitudes of shallowearthquakes,Bull.Seism.Soc.Amer.,35,57～59。
Kanamori,H.,l983,Magnitude scale and quantificaion of earthquthes,Tectonophysics,93,185～199.
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