中文摘要：

远震初至拾取是地震学研究中的关键环节,它在地震定位、核爆炸检测以及远震层析成像中起着重要的作用.基于波形相似性的远震初至拾取方法利用互相关估计各地震道的相对时差,具有抗噪和拾取精度高的特点.目前流行的各种基于波形相似性的远震初至拾取方法的原理各不相同,在时窗参数设定、稳定性和计算效率等方面存在差异,有必要对不同方法进行总结,并对其精度和效率进行评价.本文针对多道互相关方法、迭代互相关叠加方法、自适应叠加方法、台网远震体波处理方法、改进多道互相关方法等五种基于波形相似性的初至拾取典型方法的特点,对比分析了各方法的精度、稳定性及其与时窗参数的关系.实际数据的应用结果显示：在相同数据条件下,改进多道互相关方法精度最高,台网远震体波处理方法次之,再次是多道互相关方法和迭代互相关叠加方法,自适应叠加方法最低.不同方法的稳定性对互相关时窗长度变化的敏感度不同,时窗过短或者过长均会造成拾取精度和稳定性的降低.当初至震相信号的时窗长度取主周期的1~2倍时,互相关时窗恰好覆盖初至震相起跳部分的波形,各种方法拾取初至的精度接近.在实际应用中,建议根据不同的震源子波类型、频率成分、噪声水平等采用不同的初至拾取策略以提高拾取的精度和稳定性.

英文摘要：

The teleseismic first-arrival picking is a key subject in seismology.It plays an important role in earthquake location、nuclear explosion detection and seismic tomography.Waveformsimilarity based picking methods,which use cross-correlation to estimate the relative time delays of seismic traces,have the characteristics of noise resistance and high precision.In terms of principle、stability、parameter of time window and computation efficiency,current waveform-similarity based teleseismic picking methods perform differently at different situations,therefore,it is necessary to evaluate the precision and efficiency of those methods.Here,we analyzed five waveform-similarity based methods in terms of precision stability and their relation with the parameters of data window respectively.The five methods are multi-channel crosscorrelation method、iterative cross-correlation and stack method、adaptive stacking method、array processing of teleseismic body waves、modified multi-channel cross-correlation method.Field data application shows that：under the same condition of parameter setting,the modified multi-channel cross-correlation method has the highest precision,following by array processing of teleseismic body waves method,multi-channel cross-correlation method,iterative cross-correlation and stack method,and adaptive stacking method.The stability of those methods vary with the sensitivity of the crosscorrelation time window＇s length.The precision and stability of first-arrival picking will decrease,when the time window is too short or too long.When the windowing width of first arrival waveform is 1~2 times of main period,the windowed data used for cross correlation contain the first break of seismic waves,and the picking precision of different methods is similar.In practical,we suggest choosing different picking methods and/or strategies according to source wavelets,frequency content,noise levels,parameters of picking window etc.in order to increase the precision and stability of first-arrival picking.