Identification of Pb seismic phase and Conrad’s discontinuity in Hainan area
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摘要: 选取海南省地震台网2009年1月1日至2016年8月25日记录到的281次ML≥2.0地震，利用PTD方法重新定位其震源深度，采用折合走时分析海南Pb震相，并对Pb震相的速度拟合进行佐证，进而确定海南岛Pb震相的存在。结果显示，从其中的52次地震事件中可识别出57个Pb震相，其相速度为6.68 km/s，在此基础上以地震波走时方程反演得到的海南地区康拉德面的平均深度为21 km。Abstract: This paper selected 281 earthquakes with ML≥2.0 from 1 January 2009 to 25 August 2016 recorded by Hainnan seismic networks, and relocated the focal depths of the earthquakes by using PTD method. And then the Pb phase in Hainan area were analyzed by using the reduced travel time and the Pb phase velocity fitting are corroborated. As a result, the Pb phases are identified in Hainan island. The results show that, 57 Pb phases were identified from 52 of the 281 seismic events with phase velocities 6.68 km/s. Based on inversion of seismic wave travel time equation, the average depth of Conrad’s discontinuity in Hainan area is determined to be 21 km.
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Keywords:
- Pb phase /
- Hainan crust /
- Conrad’s discontinuity /
- reduced travel time /
- PTD loca-tion method
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图 2 使用PTD方法定位前、后震源深度沿纬度（上）和经度（下）方向的变化比较图
Figure 2. Comparison of focal depths of the seismic events along latitude （upper） and longitude （lower） directions before and after location by PTD method
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图 4 本文所用含有Pb震相的地震分布图
Figure 4. Seismic events distribution with Pb phase used in this paper
表 1 云南、广东和海南各省份的地壳速度模型表
Table 1 The crustal velocity model of Yunnan，Guangdong and Hainan Provinces
省份 v1/（km·s−1） v2/（km·s−1） v3/（km·s−1） H1/km H/km 云南 6.01 6.60 7.89 20 41 广东 6.00 6.87 7.96 22 33 海南 6.00 6.84 7.97 21 30 注：v1和v2分别表示第一、二层的平均速度，v3表示莫霍面的平均速度，H1表示第一层的平均厚度，H表示莫霍面的平均厚度。 
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