海南岛西南海域地壳剖面海陆联合探测研究  

The crustal profile and onshore-offshore seismic exploration in the marine area southwest to Hainan Island

作　　者：刘赛君[1,2] 曾钢平 丘学林[3] 符干 吴世敏[3,5] 叶三余 陈金海[2] E．Flueha 

机构地区：[1]海南省地震局,海口570203 [2]福建省地震局,福州350003 [3]中国科学院南海海洋研究所,广州510301 [4]Geomar, Kiel D-24148, Germany [5]中山大学地球科学系,广州510275

出　　处：《地球物理学进展》2011年第3期922-933,共12页Progress in Geophysics

基　　金：国家自然科学基金重点国际合作课题(49664011);科技部973课题(2007CB411701);海南省自然科学基金(49601);海南省重点科技计划项目任务书(080219)联合资助

摘　　要：在海南岛SW海域,利用船载大容量气枪连续发射,岸基台阵(301)与海底地震仪(OBHs)同步接收地壳深部地震波,在海岸与浅海过渡地区首次实施海陆联测,获得了最远偏移距1 30 km的岸基观测记录,与OBHs数据联合反演完成了210 km的地壳结构剖面AA'.与BB'及重磁资料对比显示,NW-SE走向的1号断层为切穿地壳的大断层、莺歌海盆地东界.自NE向SW跨越断层,地壳结构明显突变:断层带上,地壳厚度由22 km骤减至12 km,新生代沉积迅速增厚(4～11km);盆地中部地壳厚度最薄<10 km,上覆沉积盖层厚度>13 km.Moho界面埋深变化约为27～23 km.断层NE,地壳呈现为大陆型特征:自SW-NE方向,Moho界面埋深为27～28 km,地壳厚度22～27 km,上覆沉积层厚度<5 km;上地壳下部存在波速5.5～6 km/s的低速带(LVZ),厚度7～8 km,顶面埋深7～10 km.上地幔顶部P波速度7.7～7.8 km/s.将研究区与西沙海槽、雷琼及华南沿海地壳对比,Moho界面深度及地壳厚度自海向陆有显著加深、加厚的趋势.An onshore-offshore seismic exploration was carried out for the first time in the Yinggehai area southwest to Hainan Island, and seismic records with the largest offset of 130 km were obtained. Using large power shipboard airguns as the seismic sources, a number of Ocean Bottom Hydrophones （OBHs） and a land-based station array （301） were deployed on the same profile to simultaneously record the wide-angle reflected and refracted seismic waves from the deep crust. After traveltime modeling of joint on- and offshore data, the 210 km long AA＇ crustal profile was constructed. In conjunction with profile BB＇ and the gravity-magnetic data, the study results indicate the NW-SE striking No 1 Fault is a regional major fault cutting deeply through the crust and representing the eastern boundary of the Yinggehai Basin. The crustal features change sharply across the No 1 Fault from NE to SW：Near the fault zone,the crustal thickness decreases suddenly from 22 km to 12 km, and while the Cenozoic sedimentary layer thickens quickly （4～11 km） lIn the basin center, the crustal thickness decreases to a minimum of 〈 10 km, whereas the overlying sedimentary layer reaches 〉13 km thick. The Moho depth decreases from 27 km to 23 km. The crust northeast to the fault zone is of the continental type： From SW to NE direction, both the Moho depth and the crustal thickness increase gently, i.e. 27～28 km and 22～27 km respectively, with the sedimentary layer thinning to about 〈5 km. A lower velocity zone （LVZ） with P wave velocity of 5.5～6 km/s is found in the lower part of upper crust. It has a thickness of 7～8 km with its top at 7～10 km depth. On the top of upper mantle, the P wave velocity is 7.7～7.8 km/s. Comparing the crust structure of the study area with those of Xisha Trough, northern Hainan island, Leizhou Peninsula and South China coastal areas, there is an obvious trend of Moho deepening and crust thickening from ocean to continent.

关 键 词：海南岛 地壳结构 海陆联测 岸基台站 

分 类 号：P313[天文地球—固体地球物理学]