Volcano-hydrologic hazards associated with the April 2015 eruption of Calbuco volcano, Chile

与 2015 年 4 月智利卡尔布科火山喷发相关的火山水文灾害

• 批准号: NE/N007654/1
• 负责人: Vernon Manville
• 金额: $ 6.58万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN007654%2F1
• 关键词: Volcano; hydrologic; hazards; associated; April

Volcanoes generate a wide range of hazards across a variety of timescales. In addition to the more familiar primary hazards to life and infrastructure associated with eruptive activity, such as ashfall, pyroclastic density currents (hot gas and particle-charged avalanches) and lava flows, in many cases the secondary hazards that arise from the remobilisation of the loose erupted material by rain and running water after the eruption is over are more devastating, longer-lasting, and reach further afield. Lahars, gravity-driven flows of volcanic debris and water, are of particular concern due to their rapid onset, mobility, high energy, and ability to impact areas far removed from perceived zones of hazard. Since 1600 AD, lahars have been responsible for 17% of all deaths due to volcanic activity, being triggered either directly by volcanic activity (i.e. by ejection of a crater lake or melting of a summit ice cap by pyroclastic flows) or indirectly as secondary events (i.e. by rainfall remobilisation of fresh pyroclastic deposits or break-outs from volcanically-dammed lakes). However, these phenomena are amongst the most poorly understood of all volcanic hazards because of their complexity and unpredictability, hampering strategies designed to militate against their potential to cause loss or damage. A key to improving our understanding and knowledge of lahars lies in field-based studies that constrain their source conditions and initiation, and how they evolved during downstream flow, picking up and dropping sediment-load along the way and interacting with the channel margins.The recent eruption of Calbuco volcano on 22-23 April 2015, in the Southern Andes of Chile, offers an opportunity to study lahars as they happen. Calbuco is one of more than 66 known active volcanoes in the southern Andes, an area that hosts 80% of Chile's population. Historic eruptions in the area have been accompanied by multiple eruption- and rain-triggered lahars, causing most the region's eruption-related deaths in the 20th Century. As economic growth in the area continues, an increasing population and infrastructure base is becoming exposed to these hazards, creating an urgent need for better quantification and understanding of such events.We will undertake fieldwork to map and characterise the deposits of the primary, eruption-triggered hot lahars that occurred during the initial eruptive phase and destroyed bridges and infrastructure in a number of river valleys around the mountain. The eruptions also deposited a thick layer of ash and lapilli on the steep, seasonally snow-clad upper slopes of Calbuco, and the nearby cone of Osorno volcano, priming the region for an intense phase of rain-triggered remobilisation during the impending Southern Hemisphere winter when the region receives most of its annual rainfall. We will measure the properties of the ash deposits in a range of locations and instrument key monitoring sites with time-lapse cameras and rain gauges to enable us to track the response of the ash layer to rain-fall events and their combined role in lahar initiation. Repeat measurements will document the evolution of the ash layer as it degrades and is eroded over time. Further downstream, we will measure the dimensions and geometry of the lahar channels and instrument them with sensors that detect and record the ground-shaking caused by the flow events, enabling us to measure their timing, magnitude, speed, and location. Time-lapse and triggered video cameras will record vital information on flow depth and sediment concentration. This combination of data will permit, for the first time, direct correlations between conditions in lahar source zones and the resulting flows. Remote-sensed satellite data, including high-resolution optical and multispectral imagery and Sentinel-1 X radar interferometry data will be used to map the evolution of lahar paths through time and construct high-resolution digital elevation models.

火山在不同的时间尺度上会产生各种各样的危害。除了与喷发活动相关的更为常见的对生命和基础设施的主要危害外，例如火山灰、火山碎屑密度流（热气体和带颗粒的雪崩）和熔岩流，在许多情况下，由于喷发结束后雨水和流水重新流动松散的喷发物质而产生的次要危害更具破坏性、持续时间更长，并且波及更远的地方。火山泥流是由重力驱动的火山碎屑和水流，由于其发生迅速、流动性大、能量高以及能够影响远离已知危险区域的区域而受到特别关注。自公元 1600 年以来，火山活动导致的死亡人数中 17% 是由火山泥流造成的，火山泥流要么直接由火山活动引发（即火山口湖喷射或火山碎屑流融化山顶冰盖），要么间接引发次生事件（即降雨重新激活新鲜的火山碎屑沉积物或火山堰塞湖的溃决）。然而，由于这些现象的复杂性和不可预测性，这些现象是所有火山灾害中人们最不了解的现象之一，阻碍了旨在减轻其造成损失或损害的可能性的策略。提高我们对火山泥流的理解和了解的关键在于基于实地的研究，这些研究限制了它们的来源条件和引发，以及它们在下游流动过程中如何演化，沿途吸收和下降沉积物负荷以及与河道边缘的相互作用。智利安第斯山脉南部卡尔布科火山最近于2015年4月22日至23日喷发，为研究火山泥流的发生提供了机会。卡尔布科是安第斯山脉南部 66 座已知活火山之一，该地区居住着智利 80% 的人口。该地区历史上的火山喷发都伴随着多次喷发和降雨引发的火山泥流，造成了 20 世纪该地区大部分与火山喷发相关的死亡。随着该地区经济的持续增长，越来越多的人口和基础设施面临这些危害，迫切需要更好地量化和了解此类事件。我们将开展实地工作，绘制和描述在喷发初期发生的初级喷发引发的热火山泥浆的沉积物，并摧毁了山周围许多河谷的桥梁和基础设施。火山喷发还在卡尔布科陡峭、季节性积雪的上坡和附近的奥索尔诺火山锥上沉积了一层厚厚的火山灰和火山灰，为该地区在即将到来的南半球冬季（该地区将接收大部分年降雨量）期间进入由降雨引发的剧烈重新启动阶段做好了准备。我们将使用延时摄像机和雨量计测量一系列地点和关键监测点的火山灰沉积物的特性，以便我们能够跟踪火山灰层对降雨事件的响应及其在火山泥流形成中的综合作用。重复测量将记录灰烬层随着时间的推移而退化和侵蚀的演变。在下游，我们将测量火山泥通道的尺寸和几何形状，并用传感器检测和记录由流动事件引起的地面震动，使我们能够测量它们的时间、幅度、速度和位置。延时和触发摄像机将记录有关水流深度和沉积物浓度的重要信息。这种数据组合将首次允许火山泥流源区的条件与产生的流量之间存在直接关联。遥感卫星数据，包括高分辨率光学和多光谱图像以及 Sentinel-1 X 雷达干涉测量数据，将用于绘制泥流路径随时间的演变图，并构建高分辨率数字高程模型。