以新疆2次5级左右地震为震例样本，选取震中附近石河子台、石场台和乌苏台记录的2013年8月以来的气枪震源信号数据，依据反射波震相，采用互相关检测技术等，研究2次5级左右地震前走时变化特征，得到如下研究结果：①根据单双层“3400走时表”速度模型，参考理论PmP走时选取震相窗是可靠的；②2次5级左右地震前3个台站记录的PmP走时变化均出现4个月和2个月左右不同程度的低值异常过程，相对走时变化幅度约为0.1%～0.26%，距震中较近的石河子台、石场台的异常特征显著于较远的乌苏台；③2次5级左右地震前走时异常变化时间和幅度均存在差异，这可能与震级和震中位置有关。

Artificial seismic source is a high precision method of measuring underground wave velocity changes at present. Large capacity airgun has unique advantages of appropriateness to detect and monitor the subsurface structure in land area scale. We selected the air-gun signal data since August 2013 of three seismic stations at Shihezi，Shichang and Wusu which are near the epicenters of two earthquakes with MS5.0 in Xinjiang. We studied travel time variety characteristics before the two earthquakes on the basis of the seismic phase of reflection wave and cross-correlation delay technology and achieved the preliminary results as follows: (1)It's reliable to select the seismic phase window with the single-double layer velocity model of the “3400 travel time table” and reference theory PmP. (2)Before the two earthquakes，the PmP travel time variety recorded by three seismic stations all have low abnormal process of value in different degree which lasts for 4 months and 2 months，and the range ability of relative travel time is about 0.1%to 0.26%，and the abnormal features in Shihezi and Shichang seismic stations are more obvious than Wusu seismic station which is farther from the epicenters. (3)There is difference in the change time of abnormal travel time and change range before two earthquakes with MS5.0，which may have relationship with the difference of magnitude degree and epicentral location.

国家自然科学基金“呼图壁储气田充放气引起地下应力变化的地震学观测”(41474051)、新疆维吾尔自治区科研机构创新发展专项基金(2013016)和新疆地震局科学基金(201504)联合资助