摘要
在海底地震仪(OBS)记录的广角地震剖面中,经常可识别出能量强,连续性好的多次波震相.在常规OBS数据处理过程中,多次波被作为无效信号剔除,但是作为地下界面的真实反射,多次波同样蕴含着地下构造的重要信息.通过对南海海盆OBS2013-ZN测线地震数据的多次波震相进行处理分析,对多个台站Pg,Pm P和Pn震相的二次震相进行识别.以OBS06和OBS07台站为例,详细阐述了二次震相的辨别和确认过程,准确拾取了二次Pg,Pm P和Pn震相的走时数据.并通过射线追踪模拟,确定其传播路径.最后,在原有P波速度模型基础上,利用走时反演方法将初至震相和二次震相进行联合成像获得新的局部速度结构.结果显示,与初至震相结果相比,浅部沉积层和中深部的壳幔速度结构都有一定程度的变化.该研究有助于充分利用OBS数据,挖掘多次波震相特征,提高地壳结构的成像精细度.
In recent years, data obtained from ocean bottom seismographs（OBS） have played a major role in studies of the oceanic crust and mantle structure, thus greatly facilitating improved understanding of deep structures in the Earth. In addition to primary, first arrival phases, multiple seismic phases can often be detected in OBS data sections. These phases tend to have high energy and good continuity, but are often rejected as invalid signals in conventional OBS data processing. However, multiple phases can be real reflections of subsurface interfaces, and contain a large amount of important information about subsurface structures. For example, in shallow sediments with poor resolution of first arrival phases, an inversion using multiple phases can improve the resolution of the sediments. Similarly, deep multiple phases can also reflect the media characteristics near the Moho, and improve the imaging precision of crustal structures. By analyzing the measured data from seismic line OBS2013-ZN at stations OBS06 and OBS07, the secondary Pg, Pm P and Pn phases are identified behind the first arrival Pg, Pm P, and Pn phases, with travel time differences in the 1.53–1.62 s range. Analysis of waveform characteristics reveals that the amplitude of the secondary phases is more prominent, and greater than that of the first arrival phases in some cases. The waveform characteristics of these two phases are very similar in terms of apparent velocity. The overall form of the multiple phases is also approximately the same as that of the first arrivals, with a correlation coefficient of -0.8. According to the recognition characteristics described, accurate arrival times of the first arrival and secondary phases are detected in the seismic sections of stations OBS06 and OBS07. The theoretical travel time is first calculated from the secondary phases based on the fire time, offset, and reduced time of seismic phases. After repeated analysis and identification, the uncertainty in detection is set to 80–150 ms. A total of 151 se
作者
王奥星
卫小冬
阮爱国
胡昊
王伟
牛雄伟
张洁
Aoxing Wang;Xiaodong Wei;Aiguo Ruan;Hao Hu;Wei Wang;Xiongwei Niu;Jie Zhang(Key Laboratory of Submarine Geoscience, Second Institute of Oceanography, State Oceanic Administration （SOA）, Hangzhou 310012, China;Department of Earth Science, Zhejiang University, Hangzhou 310027, China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2018年第13期1235-1244,共10页
Chinese Science Bulletin
基金
国家重点研发计划(2017YFC1405104)
国家自然科学基金(41776053
41576037
41406052
91228205)
国家海洋局第二海洋研究所基本科研业务费专项(JG1602)资助
关键词
海底地震仪
多次波层析成像
二次震相
地壳结构
ocean bottom seismometer
multiple waves tomography
secondary phases
crustal structure
