西南印度洋中脊三维地震探测中炮点与海底地震仪的位置校正  

The correction of shot and OBS position in the 3D seismic experiment of the SW Indian Ocean Ridge

作　　者：敖威[1,4] 赵明辉[1] 丘学林[1] 李家彪[2] 陈永顺[3] 阮爱国 李守军[2] 张佳政[1,4] 吴振利[2] 牛雄伟[2] 

机构地区：[1]中国科学院边缘海地质重点实验室,中国科学院南海海洋研究所,广州510301 [2]国家海洋局第二海洋研究所,杭州310012 [3]北京大学地球与空间科学学院,北京100871 [4]中国科学院研究生院,北京100049

出　　处：《地球物理学报》2010年第12期2982-2991,共10页Chinese Journal of Geophysics

基　　金：中国大洋协会十一五研究课题(DYXM-115-02-3-01);国家高技术研究发展计划(863项目)(2008AA093001);国家重点基础研究计划(973项目)(2007CB411701);国家自然科学基金项目(40776025);中国科学院知识创新工程项目(KZCX2-YW-Q05-04);中国科学院南海海洋研究所领域前沿项目(LYQY200704)资助

摘　　要：在海上实施三维地震探测过程中,人工震源枪阵中心与船上GPS的距离及地震探测作业中的船行方向造成炮点实际位置与预设位置有一定偏差;自由落体投放的OBS由于海流的影响会偏离原定设计位置(投放点),因此,炮点与海底地震仪(OBS)的位置校正是三维地震结构研究中的基本环节.本文利用艏向信息校正了炮点位置;采用蒙特卡洛和最小二乘法方法对海底地震仪的位置进行了校正,并探讨了直达水波曲线特征.结果表明OBS位置一般偏离设计点1km左右,其误差范围在20m以内,校正后的OBS记录剖面展示了真实的记录情况.该研究结果为下一步西南印度洋的三维层析成像研究提供了坚实数据基础,同时为今后南海的三维深部地壳结构探测提供经验与借鉴.In a three-dimensional （3-D） seismic experiment carried out at sea, due to the distance between GPS antenna on ship and the center of air gun sources in sea water, and some environmental factors such as wind and sea current, the survey ship would adjust its heading direction which causes the shofs real position to deviate from presupposed shot track; meanwhile, real locations of OBSs on the seafloor would drift from designed points （deployed locations） since OBSs are of free-fall type and are usually affected by sea current during descending. So, the calibration of air gun shot and Ocean Bottom Seismometer （OBS） locations are basic steps for later studies on fine seismic velocity tomography. Our research focuses on the correction of shot and OBS positions with latest data from a new 3D seismic experiment in the SW Indian Ocean Ridge. The shot positions were corrected with geometric relationship among ship＇s heading, GPS antenna and the air gun array. The correction of OBS positions was based on travel times of direct water waves, and Monte Carlo and Least Square Methods were adopted. In addition, we discuss the relationship between reduced travel time curve of direct water wave and OBS deviation. Our results show that OBS locations generally drifted from the design points about 1 km, with an error range of 0-20 m and shots were adjusted to their actual positions. The research results do not only supply a fundamental database for the 3D seismic tomography in SW Indian Ocean Ridge, but also provide valuable experiences for 3D seismic survey in the South China Sea in future.

关 键 词：海底地震仪 位置校正 三维地震探测 西南印度洋中脊 

分 类 号：P714[天文地球—海洋科学]