长白山地区火山地层和火山架构及其与次生灾害和喷发趋势的关系

Similar to a skyscraper volcano can be described by their basic composing units (volcanostratigraphy) and architecture. As inherent attribute volcanostratigraphy and volcanic architecture have their own characteristics and evolution rule that provide us with incomparable clues to the trend analysis of volcanic eruption. They also impact on stability of the accumulated building and thus on the forms of related volcanic hazard. But little have been researched about them up to now. Changbaishan are dormant volcanos that may erupt at any time in the near future. Many of the lava volcanos sit high on the soft Quaternary/Neogene sediments. The unstable architecture coupled with large amount of low density pumice (<1 g/cm3) deposits are prone to resulting in secondary calamities like landslide, slump, and re-transported pyroclastic flow. The project design to study 19 well exposed volcano outcrops, measure 2 grand-canyon sections of more than 30 km long each, and re-process the data of pre-existing petroleum/geothermal boreholes, ground precision magnetic survey, and natural seismographic network. Large scale mapping work will be carried out for several selected key squares in the region. We will focus on the volcanic stratigraphic unit, boundary, and stacking pattern in order to not only highlight every single component but also to get comprehensive recognition of different volcanos. Volcanic architecture concerning landscape, construction of the main body, and structure of the feeder systems will be also studied by means of integrated geological-geophysical technique. There are about 18 eruption cycles since Oligocene in the area. Volcanic stratigraphy, boundary, architecture, and ejected component and composition will be counted in detail for each of the cycles to get the time and space sequence of the volcanos. We hope that the statistic results may tell us some of the potential features of next eruption. Primary and secondary boundaries of the volcanostratigraphy will be specially emphasized in the above sequences because the latter indicate re-transportation of the previously accumulated materials in geological history and thus a kind of "hazard" could happen in the past. They may be indicative of a past landslide, debris avalanche, joekullaups, and so on. This kind of past events can be revealed by unconformable contact surfaces between different volcanic members, i.e. secondary boundaries. Such ancient and historical recorded volcanic hazards will be addressed to the category and characteristics of the volcanostratigraphy and volcanic architecture, so as to establish the linkage between hazard characteristics and volcano natures. Potential natural disasters and their consequences related to the widely distributed volcanos will be suggested according to their presently seated situation, which can be used as a scientific guidance for the disaster prevention and mitigation engineering of the district.

火山如同摩天大厦，再复杂也可分解为基本建筑单元（火山地层）和架构两部分。地层和架构是火山固有属性，其发生发展过程和规律性是预测火山演化趋势的基础；同时它们也决定着火山堆积体的稳定性和次生灾害特点。长白山属休眠火山有再喷发的风险；其熔岩常见非稳定型火山架构（坐落在松散层之上），是滑坡和崩塌的地质根源；其碎屑堆积物含大量密度<1的浮岩，易于再搬运并引发泥石流等次生灾害。拟基于对长白山区19个典型露头和2条大峡谷长剖面的精细测量，结合已有钻孔和地面高精度磁测及天然地震资料，并对典型露头区开展大比例尺填图，用火山地层学方法研究本区火山体的地层属性（单元、界面和叠置）和架构特征（地貌、建造和结构）；实现对各类火山的分解描述和整体认知。统计渐新世以来18期火山喷发物的地层、架构及成分变化规律，支撑火山喷发趋势预测。建立火山地层、架构及就位状态与各类次生灾害的关系，为制定有效的减灾防灾规划提供科学依据。

火山如同摩天大厦，在复杂也可以分解为基本建筑单元（火山地层）和架构两部分，而长白山天池火山又是我国最具潜在喷发危险的一座活火山，故本项目以长白山火山地层和火山架构与原生、次生火山灾害的关系为总体研究方向，在长白山及临区，开展了针对火山地层三要素（界面、单元和叠置关系）、千年大喷发火山碎屑喷发物与原生火山灾害、火山架构与次生火山灾害、长白山温泉系统等的野外地质考察、取样工作以及地球化学的测定，项目的实施以火山地层界面、单元和叠置关系为切入点，从点（野外剖面点）-线（野外长剖面）-面（局部大比例尺火山地质填图）三个方面进行了深入研究，建立长白山火山群地层和架构体系，初步将长白山千年大喷发原生火山碎屑堆积物划分空落相和火山碎屑流2相9亚相，建立长白山千年大喷发原生、次生火山碎屑沉积模式，为千年大喷发火山碎屑堆积物的进一步深入研究提供了喷发物的时空分布模型。利用水化学数据和B/Cl比值将地区的热水样品分为三类来分析长白山地热系统，建立长白山地热系统成因模式。根据对长白山天池及邻区火山地质和次生火山灾害地质编图的结果，从岩性、断裂、地形地貌和水系等方面，分析火山喷出物的地质特征与这些火山物质所导致的次生火山灾害之间的相关性，建立长白山火山次生灾害与火山地质的关系。通过本项目的研究，说明长白山地区熔岩常见非稳定型构造、地区浮岩分布广泛、水系与地形地貌发育，这都为崩塌、滑坡、泥石流等次生火山灾害的发生提供良好条件，建立火山地层、架构及就位状态与各类次生火山灾害关系，为灾害评价与防治和制定有效的减灾防灾规划提供科学依据。