中文摘要：

由概率论推导提出能够纠正截短偏差的修正算法,工程应用前为明确2种算法适用范围,先采用2种算法由实测半迹长分布估算直径期望,然后对比2种算法估算的直径期望与真实直径期望的相对误差,进行21组对比试验。结果表明：Priest-Zhang算法估算的直径期望是截短值的线性递增函数,修正算法估算的直径期望是截短值的水平线性函数;截短值较小时,2种算法接近,采用前者已能够获得较高精度,纠正截短偏差意义不大;截短值较大时后者明显更精确,纠正截短偏差能够大幅提高精度,应选用后者。汶川工程实例表明：当截短值为0.1 m时,2种算法具有高精度且估算结果接近,值得推广。

英文摘要：

A new Priest-Zhang Algorithm was derived from the combination of Priest Equation and Zhang Equation.Priest-Zhang Algorithm brought in truncation bias,and Revised Priest-Zhang Algorithm was proposed from probability theory.Truncation bias was corrected in it.Applicability of both algorithms needs to be defined.First,mean diameter was estimated from distribution of observed semi-trace length by both algorithms.Secondly,the relative errors of estimated mean diameter were compared between both algorithms.21 sets of experiments were carried out.The results show that the estimated mean diameter by Priest-Zhang Algorithm is a linear increasing function of truncation threshold,while that by Revised Algorithm is a horizontal linear function.When truncation threshold is small the estimated mean diameters by both algorithms are similar,and Priest-Zhang Algorithm can be high of accuracy.When truncation threshold is large Revised Algorithm is more accurate,and the correction of truncation bias is significant.In this case Revised Algorithm is prior choice between the two algorithms.A case study in Wenchuan verifies that when truncation threshold is 0.1 m two algorithms are high of accuracy and similar in estimated diameters.The two new diameter algorithms are worth popularizing.