南海IODP 367-368钻探区深地震探测的OBS站位设计分析
作者简介:王强(1987—), 男, 甘肃省陇西县人, 博士在读, 主要从事海洋地球物理研究。E-mail: wangqiang@scsio.ac.cn
收稿日期: 2017-01-20
要求修回日期: 2017-03-13
网络出版日期: 2018-02-02
基金资助
国家自然科学基金项目(41730532、91428204、41576070、41376063)
国家自然科学基金委员会共享航次(NORC2015-08)
Analysis and tests on an OBS layout for deep seismic survey in the IODP legs 367-368 area of the South China Sea
Received date: 2017-01-20
Request revised date: 2017-03-13
Online published: 2018-02-02
Supported by
Natural Science Foundation of China (41730532, 91428204, 41576070, 41376063)
National Natural Science Foundation of China Open Research Cruise (NORC2015-08)
Copyright
借助于国际大洋发现计划平台, 于2017年2月—6月间在南海实施第三次科学钻探(IODP 367-368航次)。海底地震仪(OBS)深地震探测和国际大洋发现计划(IODP)钻探成果相结合, 可以对南海北部洋陆转换带(COT)边界及地质属性的确定提供更好、更全面的深部地质过程解释。文章基于IODP 367-368钻探提出的三种可能设想(下地壳出露、最老洋壳出露、上地幔出露), 分别建立了三种初始速度模型。利用Rayinvr及Tomo2d软件, 对每一种初始模型分别开展了不同OBS间距的射线追踪和走时模拟测试对比, 以及模型的分辨率测试。测试结果表明: OBS间隔为7km比间隔为10km具有更好的射线路径与密度覆盖; 对于上地幔出露模型, 需要足够长的探测测线(>100km), 才能有效得到30km深处信息; 分辨率测试说明, OBS间距需要设置小于或等于7km时, 才能有效分辨20km速度异常体(即模糊带)。
王强 , 赵明辉 , 张佳政 , 孙龙涛 , 丘学林 . 南海IODP 367-368钻探区深地震探测的OBS站位设计分析[J]. 热带海洋学报, 2018 , 37(1) : 90 -97 . DOI: 10.11978/2017011
The third scientific drilling in the South China Sea (SCS) will be carried out during Feb. to Jun. 2017 under the system of the International Ocean Discovery Program (IODP), namely, IODP Legs 367 and 368. The drilling project will improve the research on geology and geophysics of the SCS and bring it to an unprecedented stage. The combination of Ocean Bottom Seismometers (OBS) deep seismic survey with IODP drilling data will improve drilling achievement, and contribute greatly to our understanding of the specific mechanism of rifting and breakup processes in the northern SCS. We first built three original velocity models based on the three geological presumptions of IODP Legs 367 and 368 as follows. 1) the exhumed lower crust, 2) the oldest oceanic crust and 3) the exhumed upper mantle. Second, the ray-tracing and travel-time modelling were performed for different OBS intervals with employment of Rayinvr and Tomo2d software, as well as check-board tests for the models. The testing results suggest that the ray-tracing paths and ray density with the 7 km interval of OBS stations are better than those with the 10 km interval. However, the seismic survey line is 100 km, enough in length to make sure to detect the crustal structure at 30 km depth. And the results of check-board tests show that the 7 km interval of OBS stations is necessary to difference the 20-km-in-size velocity anomaly, which is the uncertainty zone in the seismic profile. The design analysis on the optimal deployment scheme of OBS stations will not only provide a good suggestion for the design of future seismic survey, but also contribute to our understanding of the mechanism of rifting and breakup processes in the SCS.
Fig. 1 Map for designed drilling wells of IODP expedition Legs 367-368 in the South China Sea. The black dashed and solid lines show water depth contours of 1000 and 3000 m, respectively. The magnetic anomalies in orange and purple colors are referenced by Briais et al (1993) and Li et al (2014), respectively. Red and white pentagrams represent designed and alternative wells (Sun et al, 2015, 2016), respectively. Lines 1530 and 1555 are two multi-channel seismic profiles across the designed drilling wells图1 南海IODP 367-368航次设计井位位置图 |
Fig. 2 Multi-channel seismic profile of Line 1555 across the designed drilling wells of IODP expedition Legs 367-368. (a) the original profile of Line 1555, with the blue frame showing the domain for building the initial models in |
Fig. 3 Three original velocity models based on three geological types of the COT. (a), (b) and (c) refer to the exhumed lower crust, the oldest oceanic crust and the exhumed continental upper mantle, respectively. The black box shows the domain of obscure zone in |
Fig. 4 Comparison of ray-tracing and travel-time simulation between 10 km and 7 km intervals of designed OBS stations based on the initial model 1 ( |
Fig. 5 Comparison of ray-tracing and travel-time simulation between 10 km and 7 km intervals of designed OBS stations based on the initial model 2 ( |
Fig. 6 Comparison of ray-tracing and travel-time simulation between 10 km and 7 km intervals of designed OBS stations based on the initial model 3 ( |
Fig. 7 Check-board test results of the 20-km-in-size velocity anomaly body. (a) and (b) are the input and output models with 10-km OBS interval; and (c) and (d) are the input and output models with 7-km OBS interval, respectively. The grid size is 15 km×5 km图7 速度异常体尺寸为20km时的初始地质模型的分辨率测试 |
The authors have declared that no competing interests exist.
[1] |
|
[2] |
|
[3] |
|
[4] |
|
[5] |
|
[6] |
|
[7] |
|
[8] |
|
[9] |
|
[10] |
|
[11] |
|
[12] |
|
[13] |
|
[14] |
|
[15] |
|
[16] |
|
[17] |
|
[18] |
|
[19] |
|
[20] |
|
[21] |
|
[22] |
|
[23] |
|
/
〈 |
|
〉 |