How turbidity current frequency and character varies down a fjord‐delta system: Combining direct monitoring,deposits and seismic data

Submarine turbidity currents are one of the most important processes for moving sediment across our planet; they are hazardous to offshore infrastructure, deposit petroleum reservoirs worldwide, and may record tsunamigenic landslides. However, there are few studies that have monitored these submarine flows in action, and even fewer studies that have combined direct monitoring with longer‐term records from core and seismic data of deposits. This article provides one of the most complete studies yet of a turbidity current system. The aim here is to understand what controls changes in flow frequency and character along the turbidite system. The study area is a 12 km long delta‐fed fjord (Howe Sound) in British Columbia, Canada. Over 100 often powerful (up to 2 to 3 m sec^?1) events occur each year in the highly‐active proximal channels, which extend for 1 to 2 km from the delta lip. About half of these events reach the lobes at the channel mouths. However, flow frequency decreases rapidly once these initially sand‐rich flows become unconfined, and only one to five flows run out across the mid‐slope each year. Many of these sand‐rich, channelized, delta‐sourced flows therefore dissipated over a few hundred metres, once unconfined, rather than eroding and igniting. Upflow migrating bedforms indicate that supercritical flow dominated in the proximal channels and lobes, and also across the unconfined mid‐slope. These supercritical flows deposited thick sand beds in proximal channels and lobes, but thinner and finer beds on the unconfined mid‐slope. The distal flat basin records far larger volume and more hazardous events that have a recurrence interval of ca 100 years. This study shows how sand‐rich delta‐fed flows dissipate rapidly once they become unconfined, that supercritical flows dominate in both confined and unconfined settings, and how a second type of more hazardous, and much less frequent event is linked to a different scale of margin failure.     

中国典型粘黄土区地质灾害风险评估危险性影响因素分析

地层岩性、岩土体结构及其工程地质特性为黄土区地质灾害提供了物质基础,黄土斜坡的坡型、坡度、坡高、阶地等地形地貌因素为地质灾害提供了边界条件,人类工程活动和降雨为黄土区地质灾害提供了触发条件。黄土地形地貌、地层岩性、岩土体结构类型及其工程地质特性、水文地质条件等为粘黄土区地质灾害形成的内在因素;降雨、人类工程活动等为其诱发因素。     

四川省地质灾害防治能力建设现状与对策研究

加强突发地质灾害的应急防治能力建设,切实提高各级地质环境监测站地质灾害防治能力建设水平,是完善我省地质环境管理体系,确保各级政府提高地质环境管理工作决策水平和效率的先决条件。通过对四川地质灾害防治工作面临的严峻形势以及各级地质环境监测站能力建设现状的分析,结合经济社会发展以及地质环境管理工作的实际,提出了加强地质灾害防治能力建设的对策及措施建议。     

地质灾害活动强度评估的原理、方法和实例

为了探索区域群发地质灾害活动强度评价的原理、方法和指标体系,从地质灾害强度的基本涵义和快速测量的技术要求2个方面简要地分析了影响群发地质灾害活动强度的主要指标和参数,并参考地震震级计算和划分的(宏观)依据,初步提出了以地质灾害分布最大面密度为衡量区域地质灾害活动强度指标的基本思路和分级标准,建立了地质灾害活动强度指数(GHI—geohazard index )8级划分标准;初步提出了快速统计估算地质灾害最大面密度的2种基本方法,即栅格法和自然斜坡(流域)统计法。结合汶川Ms8.0级地震诱发地质灾害、陕西省宁陕县城2003年暴雨诱发地质灾害和宝鸡市地质灾害活动强度分析评价,简要地讨论了在地质灾害强度评价指标、最大面密度统计测量方法及其代表性等方面存在的问题,强调地质灾害强度(GHI)指标评价分级还处于探索研究的开始阶段,还需要在实践中不断修改完善。     

滇西大理至瑞丽铁路龙陵段主要的地质灾害类型及其发育规律

大理—瑞丽铁路龙陵段地处云南高原滇西峡谷区,处于怒江与伊洛瓦底江两大水系分水岭地带。地貌复杂、峡谷深切,新构造运动十分强烈,地震活动频繁。该区的降雨主要集中在5～10月份,降雨强度大且集中。复杂的地质环境及降雨、人类活动等外部因素使该地区成为崩塌、滑坡、泥石流等地质灾害多发区,常冲毁稻田、山林,发生毁坏桥梁公路、毁坏房屋及人员伤亡的事故。阐述了大理—瑞丽铁路龙陵段主要地质灾害的分布、形成条件及发育规律,为大理—瑞丽铁路工程规划建设和测区经济社会发展提供基础地质资料和科学依据。     

钒矿带矿区地质灾害危险性评价——以陕西山阳-商南钒矿带中村镇钒矿开采区为例

在查明地质灾害孕灾背景、发育现状、矿区开采现状的基础上，基于定性结合定量的评价方法，开展了矿区地质灾害危险性评价.基于评价结果和野外调查情况，总结采矿活动对矿区主要地质灾害的影响.主要成果如下：1）总结了研究区地质灾害的发育及分布特征；2）综合分析矿区孕灾环境及地质灾害致灾因子，构建了研究区危险性评价指标体系，以ArcGIS为工作平台，以斜坡单元为最小评价单元，进行了由地质灾害易发性到地质灾害危险性的评价；3）针对评价结果，理论分析了采矿活动对滑坡、崩塌、泥石流及塌陷等灾害发生的影响方式.     

藏东高山峡谷地带地质灾害危险性评价——以西藏贡觉县为例

在西藏贡觉县地质灾害调查的基础上,开展研究区内的地质灾害危险性评价.根据研究区地质地理环境特征,优选出7个评价因子：坡度、历史地质灾害密度、工程岩组、线性构造密度、植被覆盖度、河网密度、年均降雨量,并建立分级标准.利用GIS技术对空间数据的采集和分析功能,结合数理统计的方法原理,对研究区进行了地质灾害危险性定量评价,揭示区内地质灾害空间分布规律.     

Overview Landslide Hazard Assessment of China

In recent years, China has suffered serious geological disasters, most of slope movements due to complex geology, geomorphology, unusual weather conditions, and large-scale land explorations during high speed economic development. According to geological hazard investigations organized by the Ministry of Land and Resources of China, there are 400 towns and more than 10000 villages under the threatening of those landslide hazards. This paper presents the overview landslide hazard assessment in terms of GIS, which aims to evaluate the overview geohazard potentials, vulnerabilities of lives and land resources, and risks in conterminous China on the scale of 1 : 6 000 000. This is the first overview landslide hazard potential map of China.     

滇西大理至瑞丽铁路龙陵段主要的地质灾害类型 及其发育规律

大理—瑞丽铁路龙陵段地处云南高原滇西峡谷区,处于怒江与伊洛瓦底江两大水系分水岭地带。地貌复杂、峡谷深切,新构造运动十分强烈, 地震活动频繁。该区的降雨主要集中在5～10 月份, 降雨强度大且集中。复杂的地质环境及降雨、人类活动等外部因素使该地区成为崩塌、滑坡、泥石流等地质灾害多发区,常冲毁稻田、山林,发生毁坏桥梁公路、毁坏房屋及人员伤亡的事故。阐述了大理—瑞丽铁路龙陵段主要地质灾害的分布、形成条件及发育规律, 为大理—瑞丽铁路工程规划建设和测区经济社会发展提供基础地质资料和科学依据。     

南海琼东南深水海区地质灾害类型与特征

南海琼东南深水海区是南中国海石油天然气资源潜在储量较为丰富的地区,油气勘探开发的力度正日益加大。但是,该海区处于南海大陆坡与西沙海槽区域,海底水深大,地形变化剧烈,水体动力环境和海底地质条件复杂,引发地质灾害的触发机制丰富,稍有疏忽,将给石油钻井平台带来巨大损失。在收集有关资料的基础上,对海底的地质环境务件作了研究,发现了一些有可能发生或潜在的地质灾害类型,并对其特征作了描述,以引起有关方面在石油钻井钻前井场工程地质调查和评价时予以重视。