华南海陆过渡带的地壳结构与壳内低速层  

Crustal structure and its low-velocity layer in transition zone of South China

作　　者：赵明辉[1] 丘学林[1] 徐辉龙[1] 夏戡原[1] 施小斌[1] 叶春明[2] 夏少红[1] 

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,广东广州510301 [2]广东省地震局,广东广州510070

出　　处：《热带海洋学报》2006年第5期36-42,共7页Journal of Tropical Oceanography

基　　金：中国科学院知识创新工程项目(KZCX3-SW-234);广东省自然科学基金项目(5219912;021557);中国科学院南海海洋研究所领域前沿项目(LYQY200302);中国科学院边缘海地质重点实验室基金项目(MSGL0604)

摘　　要：壳内低速层与地质构造背景的联系已逐渐引起人们的重视。华南沿海众多的地震测深剖面揭示出地壳不同深度上存在着壳内低速层。根据海陆联合深地震探测取得的数据,通过射线追踪和走时模拟方法,获得了沿OBS-2001测线海陆过渡带的地壳结构。根据低速层的走时间断特性辨识了海区地壳中部低速层。剖面中壳内低速层分布在新塘经南澳岛至南澳岛东南约150.0 km的陆架区,尖灭于东沙隆起,其顶面深度为10.0—18.0 km,速度为5.5—5.9 km.s-1,与上、下岩层的速度差均为0.5 km.s-1,其空间展布较为稳定,厚度为3.0—4.0 km,推断其为华南沿海陆上低速层的延伸,含水矿物脱水和部分熔融可能是引起该区壳内低速层弹性波速下降的主要因素。该区壳内低速层的研究对于深入认识岩石圈结构及动力学作用过程具有重要的地质地球物理意义。Low-velocity layer in crustal structure has a close relationship with tectonic and dynamic settings. Many seismic profiles in South China have demonstrated that low-velocity layer generally exists in the middle crust. The onshore-offshore deep seismic experiment was implemented in the transition zone between South China and northeastern South China Sea in 2001. By analyzing the seismic data from land stations and OBSs, different seismic phases were identified, and their travel time arrivals were modeled by ray-tracing program MacRay. Then the crustal structure was obtained along OBS-2001 profile, and the low-velocity layer was identified based on its travel-time gap. The low-velocity （5.5-5.9kin·s^-1 ） layer exists in the bottom of upper crust （10.0 18.0 km deep） from Xintang area to 150.0 km SE of the Nanao Island, with a thickness about 3.0-4.0 kin. It has a relatively stable spacial distribution and was deduced to be the extensionof the low-velocity layer of South China. The dehydration of water-containing minerals and the presence of melted or partially melted rock in the crust maybe the main factors that reduce the P-wave velocity.

关 键 词：海陆过渡带 地壳结构 壳内低速层 华南沿海 

分 类 号：P736.1[天文地球—海洋地质]