云南省区域数字地震遥测台网远震参数测定
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摘要
利用云南省区域数字地震遥测台网记录到的资料对远震的定位方法进行了研究。采用“分离变量法",将震源参数分为发震时间、震中位置和震源深度三类变量,相对独立进行计算,这就减少了Geiger法中,各类变量因不同权重而产生的互相干扰以及因初始解不好引起的迭代不收敛的问题,改善了定位精度。由于大地震的地震波初动清楚,可精确测定初动到时,仅用经过台站高程走时改正和台站综合走时改正后的初动到时即可精确测定零深度时的震中位置。再根据测定的零深度震中位置,查出台网最小到时子台的S波到时S0,它与该台的实际S波到时Sh的差可有效判定地震是否深源地震和计算震源深度。为了保持地震震级定义的一致性,采用数字地震仪系统的传递函数(包括幅频特性和相频特性)对实测数字地震记录进行仿真,得到真正的地动速度,再由计算机自动检测定地动速度最大面波振幅并计算震级MS。
A teleseismic location method, Parameter Separating Method, was studied using Yunnan Regional Digital Telemetric Seismic Network data. Different from the Geiger method, this method divides focal parameters into three classes: occurrence time, epicenter location and focal depth, and gives the parameters a relatively independent calculation. So, it gets rid of the disturbance produced by different weights of the parameters, resolves the problem that the iterative process isn’t convergent, and improves the location precision. From clear initial motion of P-wave we can accurately measure first arrival time, then get the epicenter location at depth zero only from the first arrival time corrected with the elevation travel time and comprehensive travel time at the station. On the basis of determined epicenter location and the difference between the theoretical P-wave travel time (S 0) and practical P-wave travel time (S h) at some station, we can judge whether the shock is a deep focus one and calculate its focal depth. To keep the consistency of magnitude from digital records with that from simulation records, we also made a emulation of observed digital seismic records using the transfer function of the digital seismograph system, and got real ground motion velocities.After that, the maximum surface wave amplitude of the ground motion and the magnitude (M S) would be checked and calculated automatically by computer.
A teleseismic location method, Parameter Separating Method, was studied using Yunnan Regional Digital Telemetric Seismic Network data. Different from the Geiger method, this method divides focal parameters into three classes: occurrence time, epicenter location and focal depth, and gives the parameters a relatively independent calculation. So, it gets rid of the disturbance produced by different weights of the parameters, resolves the problem that the iterative process isn’t convergent, and improves the location precision. From clear initial motion of P-wave we can accurately measure first arrival time, then get the epicenter location at depth zero only from the first arrival time corrected with the elevation travel time and comprehensive travel time at the station. On the basis of determined epicenter location and the difference between the theoretical P-wave travel time (S 0) and practical P-wave travel time (S h) at some station, we can judge whether the shock is a deep focus one and calculate its focal depth. To keep the consistency of magnitude from digital records with that from simulation records, we also made a emulation of observed digital seismic records using the transfer function of the digital seismograph system, and got real ground motion velocities.After that, the maximum surface wave amplitude of the ground motion and the magnitude (M S) would be checked and calculated automatically by computer.
引文
[1]GeigerL.Probabilitymethodforthedeterminationofearthquake epicentersfromarrivaltimeonly[J].Bull.St.Louis.Univ,1912,(8):60-71.
[2]田明.地震定位研究综述[A].见:北京大学政学者论文集[C].北京:北京大学出版社,2001,254-265.
[3]颜其中,何家斌,高杰.数字地震仪系统传递函数的一种计算方法[J].地震学报,2003,25(6):667-671.
[4]李桂华,刘国华,何家斌,等.昆明数字遥测台网近震震级的测定[J].地震地磁观测与研究,2003,(24):32-38.
[2]田明.地震定位研究综述[A].见:北京大学政学者论文集[C].北京:北京大学出版社,2001,254-265.
[3]颜其中,何家斌,高杰.数字地震仪系统传递函数的一种计算方法[J].地震学报,2003,25(6):667-671.
[4]李桂华,刘国华,何家斌,等.昆明数字遥测台网近震震级的测定[J].地震地磁观测与研究,2003,(24):32-38.
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