二滩水电站地震遥测台网持续时间震级的研制

Study on estimate of magnitude of local earthquake from signal duration for Eetan Seismic Telemetry Network

利用二滩水电站地震遥测台网的速度量和位移量观测记录，收集了震级ＭＬ为０．４～５．４的４６０次地震（Δ＜２１０ｋｍ）的振动持续时间３５００多条，制作了该台网的持续时间震级公式和便查表。在方法上，不同于通常的按一次或两次曲线拟合，而采取计算机自动分段按折线拟合的方法，以阻尼最小二乘法完成其计算；在资料上，先分台制作８个子台的持续时间震级公式，在此基础上选择仪器、台基及公式中参数相近的子台，制作了适用于该台网的平均持续时间公式。经过３８次地震实地检验，所给震级ＭＤ与四川台网水平地动位移确定的ＭＬ相差一般小于０．１。为二滩台网确定震级，尤其是限幅记录的震级，提供了较为可靠的依据和方便。

We suggest a set of magnitude formula and a convenient magnitude table of local earthquake from signal duration of oscillation for the Telemetric Seismic Network at Eetan Hydroelectric Station, using more than 3 500 observed records from 460 earthquakes with local magnitude M L of 0 4～5 4 occurred in or nearby Ertan Network ( Δ <210 km).In method, it is different from usual linear or square curve fits, but it adopts segmental straight line with several pieces by using the damped least square method so as to match such a large number of signal duration data. In compution, we obtain, at first, a set of magnitute formula for 8 sub stations separately, then we derive a set of average formula for the whole network selecting 7 sub stations with similar parameters such as seismograph type and amplification, base rocks of station, fitted formula coeffient et al. We test the magnitude formula obtained by means of 38 events. The results show the differences between the present estimated duration magnitude M D and the local magnitude M L from Sichuan Network based on the horizontal ground displacements are less than 0 1 unit generally. In conclusion, the present suggested magnitude formulas from signal duration are quite suitable for the determination of local earthquake in Ertan Telemetric Seismic Network, especially, for the very big events with the limited amplitude signals.