中文摘要：

利用地震P波初始信息快速估算震级是地震预警系统中的重要部分之一，文中详细介绍了地震预警研究中常用的两种卓越周期估算震级方法：τ_pmax方法和τc方法。为了评估这两种方法哪一种震级估算精度更高，文中通过设置不同的估算震级时间窗以及不同的滤波频带，利用震级范围4．1～7．9的22次地震的强震观测记录对这两种方法进行了比较分析。比较的结果表明：本文计算得到的τpmax值和τc。值与震级之间均存在线性比例关系，与前人的研究结果一致；在相同的0．075—3Hz带通滤波条件下，利用P波触发后3s地震记录计算的τc值可获得最优的震级估计结果，τc与震级的相关系数为0．78，标准差为0．16。仅经过0．075Hz高通滤波得到的τpmax值与震级的线性相关度比0．075-3Hz带通滤波得到的τpmax值与震级的线性相关度低，而是否经过低通滤波对τc值与震级的线性比例关系没有影响。建议在地震预警系统中优先采用3sτc方法作为震级估算方法。

英文摘要：

One of the critical technologies of earthquake early warning is determining the size of an earthquake from the first a few seconds after the P-wave arrival. Currently, there are two magnitude estimating approaches using pre- dominant period for earthquake early warning, τpmax method and 1＂c method. In order to explore which method is with higher precision, we compare τpmax method with 7c method from 22 earthquakes in United States with magnitude ran- ging from 4.1 to 7.9, through setting different time windows for calculating τpmax andτc values and band of filtering for earthquake records. Our results show that scaling relations between the two predominant period parameters,τpmax andτc, calculated from P-wave arrivals and earthquake magnitude are consistent with the previous researches. It is found that τc method has higher precision than τpmax and τc method with the same filtering band, and has best result in magnitude estimation resulting in a correlation coefficient of 0.78 and a standard deviation of 0.16 using 3 sec- onds signal after the P-wave arrival. We also found that τpmax method with low-pass filtering had higher accuracy than τc method without low-pass filtering. There is no distinct effect on magnitude estimation using τc with whetherlow-pass filtering or not. We recommend τc method using 3 seconds signal after the P-wave arrival as the preferen- tial magnitude estimating method for earthquake early warning.