寻找并确认更深的余震，对认识汶川主震的深部构造环境、应力状态具有一定的意义。已有研究表明，绝大多数汶川地震余震深度在20km以内，但近期的研究提出了2个余震可能深于30km的证据，为了确认这2个疑似深震的震源深度，本文通过计算理论地震图测试了震源深度及震中距对P波偏振的影响，并与实际观测的P波偏振信息进行对比分析。此外，还使用近震深度震相sPL波拟合的方法来测定震源深度，确认了这2个地震的深度在10～15km范围。

Accurate depths of aftershocks are a help to understand deep tectonic structure and stress field beneath the Longmenshan fault. Depths of most aftershocks of the Ms8.0 Wenchuan earthquake were reported in upper crust （〈25km）. Recently, some observations were regarded as evidences to two deep aftershocks （ 〉 30km）. We analyzed broadband seismogram of these events based on P wave polarity and sPL waveform, but they both support the depths less than 20km. To confirm the error source, we investigated residuals of other events with high location precision and considered dominant errors arising from inaccuracy locations of some temporal seismic stations.[著者文摘]

本项研究得到中国科学院动力大地测量学重点实验室基金（L10-04）和国家自然科学基金（41104032）项目资助