Several cruises of gas hydrate resource survey have been carried out at Qiongdongnan continental slope, Xisha trough as well as Shenhu area since 1999. The geological data revealed that sub-marine slides were developed in the northwestern continental slope of the South China Sea. Three landslide zones were identified based on high-resolution single-channel seismic profiles and multi-beam echo sounding data. This paper discusses in detail the characters and formation mechanism of these landslide zones. Shenhu landslide zone is about 100 km long, 25km wide, and is oriented along the NE-SW direction at a water depth of 400?600m. It has close relationship with gas hydrate dissociation and stable geological engineering condition. Xisha trough northern slope landslide zone is about 90 km long, 15?20km wide, and has an EW trending at a water depth of 2000?3100m. It was formed by huge thickness sediment movement under process of gravity. Xisha trough slide has a better geological engineering condition, but its slide fan still can be seen in some unstable segments. Qiongdongnan continental slope landslide zone is about 150 km long, 5?10km wide, and is oriented in a NE-SW direction at a water depth of 250?850m. It was affected by active faults and bottom current erosion, and has an unstable geological condition. The results of this study can be a scientific base for gas hydrate survey and exploration.
[1] 杨春霞, 王春民, 王圣洁. 南海北部灾害地质稳定度评价模型[J]. 中国地质灾害与防治学报, 2006, 17(1): 77?79.
[2] 鲍才旺, 姜玉坤. 中国近海海底潜在地质灾害类型及其特征[J]. 热带海洋, 1999, 18 (3): 24?31.
[3] 冯志强, 冯文科, 薛万俊. 南海北部地质灾害及海底工程地质条件评价[M]. 南京: 河海大学出版社, 1996: 1?178.
[4] CANALS M, LASTRAS G, URGELES R, et al. Slope failure dynamic sand impacts from seafloor and shallow sub-seafloor geophysical data: case studies from the COSTA project [J]. Marine Geology, 2004, 213(1-4): 9-72.
[5] MASLIN M, NAJA M, BILAL H, et al. Sea level and gas hydrate controlled catastrophic sediment failures of the Amazon Fan [J]. Geology, 1998, 26(12): 1107-1110.
[6] 夏真, 郑涛, 庞高存. 南海北部海底地质灾害因素[J]. 热带海洋, 1999, 18(4): 91-95.
[7] WILSON C K, LONG D, BULAT J. The morphology, setting and processes of the Afen Slide[J]. Marine Geology, 2004, 213: 149-167.
[8] URGELES R, LEYNAUD D, LASTRAS G, et al. Back-analysis and failure mechanisms of a large submarine slide on the Ebro slope, NW Mediterranean [J]. Marine Geology, 2006, 226: 185-206.
[9] SULTAN N, VOISSET M, MARSSET B, et al. Potential role of compressional structures in generating submarine slope failures in the Niger Delta[J]. Marine Geology, 2007, 237: 169-190.
[10] THIEM R, BERNT SEN J, ELDEVIK T, et al. Gas exploration beyond the shelf break: An oceanographic challenge [J]. Environmental Modelling & Software, 2006, 21: 136-141.
[11] BROWN H E, HOLBROOK W S, HORNBACH M J, et al. Slide structure and role of gas hydrate at the northern boundary of the Storegga Slide, off shore Norway [J]. Marine Geology, 2006, 229: 179-186.
[12] 张树林. 珠江口盆地白云凹陷天然气水合物成藏条件及资源量前景[J]. 中国石油勘探, 2007(6): 23-27.
[13] 沙志彬, 杨木壮, 梁劲, 等. 南海北部陆坡海底异常地貌特征与天然气水合物的关系[J]. 南海地质研究, 2003(14): 29-34.
[14] 吴时国, 姚根顺, 董冬冬, 等. 南海北部陆坡大型气田天然气水合物的成藏地质构造特征[J]. 石油学报, 2008, 29(3): 324-328.
[15] 吴时国, 姚伯初. 天然气水合物赋存的地质构造分析与资源评价[M]. 北京: 科学出版社, 2008: 16-20.
[16] 万玲, 姚伯初, 吴能友, 等. 南海西部海域新生代地质构造[J]. 海洋地质与第四纪地质, 2005 , 25(2): 45-52.
[17] 黄维, 汪品先. 南海沉积物总量的统计方法与结果[J]. 地球科学进展, 2006(5): 465-473.
[18] 夏伦煜, 麦文, 赖霞红, 等. 莺歌海?琼东南盆地第四纪初步研究[J]. 中国海上油气1989, 2(3): 21-28.
[19] 汪品先, 夏伦煜, 王律江, 等. 南海西北陆架的海相更新统下界[J]. 地质学报, 1991(2): 176-168.
[20] 吕明. 莺?琼盆地低位沉积模式的新探讨[J]. 中国海上油气: 地质, 2002, 16 (4): 221-230.
[21] 陆敬安, 杨胜雄, 吴能友, 等. 南海神狐海域天然气水合物地球物理测井评价[J]. 现代地质, 2008, 22(3): 447-451.
[22] 王宏斌, 张光学, 杨木壮, 等. 南海陆坡天然气水合物成藏的构造环境[J]. 海洋地质与第四纪地质, 2003, 23(1): 81-86.
[23] 张光学, 祝有海, 梁金强, 等. 构造控制型天然气水合物矿藏及其特征[J].?现代地质, 2006, 20(4): 605-612.
[24] 雷新民, 张光学, 郑艳. 南海北部神狐海域天然气水合物形成及分布的地质因素[J]. 海洋地质动态, 2009, 25(5): 1-9.
[25] 施小斌, 周蒂, 张毅祥, 等. 南海西沙海槽岩石圈的密度结构与热流变结构[J]. 热带海洋学报, 2002, 21(2): 23-31.
[26] 何廉声, 王光宇, 石效超. 西沙海槽-新生代裂谷[J]. 地质论评, 1980, 26(6): 486-489.
[27] 姚伯初, 曾维军, 陈艺中, 等. 南海西沙海槽, 一条古缝合线[J]. 海洋地质与第四纪地质, 1994, 14(1): 1-10.
[28] 陈道华, 蒋少涌, 刘坚. 西沙海槽表层沉积物地球化学特征及其地质意义[J]. 海洋地质与第四纪地质, 2005, 25(2): 37-44.
[29] 刘方兰, 吴庐山. 西沙海槽海域地形地貌特征及成因[J]. 海洋地质与第四纪地质, 2006, 26(3): 7-14.
[30] 庞雄, 陈长民, 朱明, 等. 深水沉积研究前缘问题[J]. 地质论评, 2007, 55(1): 36-44.
[31] 李西双, 刘保华, 赵月霞, 等. 海底活动断裂研究方法及我国近海活动断裂研究[J]. 海洋地质动态, 24(3): 9-13.
[32] 赵明辉, 丘学林, 叶春明, 等. 南海东北部海陆深地震联测与滨海断裂带两侧地壳结构分析[J]. 地球物理学报, 2004, 47(5): 845-852.
