Mapping block-and-ash flow hazards based on Titan 2D simulations: a case study from Mt. Taranaki, NZ
Mapping block-and-ash flow hazards based on Titan 2D simulations: a case study from Mt. Taranaki, NZ
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基于 Titan 2D 模拟绘制块体和灰流危害图：新西兰塔拉纳基山的案例研究
DOI：
10.1007/s11069-009-9440-x
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发表时间：
2010
期刊：
影响因子：
3.7
通讯作者：
V. Neall
中科院分区：
文献类型：
--
作者：
J. Procter;S. Cronin;T. Platz;A. Patra;K. Dalbey;M. Sheridan;V. Neall
用于模拟质量流的数值模型通常侧重于准确预测单个流或崩塌事件的路径、行进时间和淹没。当考虑火山造成的流域灾害时，由于经常面临多种可能的情况，情况变得很复杂。在过去的 800 年里，塔拉纳基山/埃格蒙特山的许多穹顶生长和塌陷事件导致了块灰流 (BAF) 的形成和安置。每个 BAF 都通过火山口边缘的缺口指向西北。最近发生在公元 1880 年代和公元 1755 年的穹顶倒塌事件淹没了西北侧，流出长度距源头 10 公里。未来此类活动可能会对塔拉纳基地区的社区、基础设施和经济产生毁灭性影响。灾害规划涉及根据过去火山流淹没的区域构建火山灾害地图，而很少考虑当今的地形。这里，采用数值地球物理质量流建模方法来预测塔拉纳基山西北地区未来类似 BAF 事件的危害。 Titan2D 程序包含“浅水”、基于连续溶液的颗粒流模型。这种方法所需的流动力学特性包括内部摩擦和基础摩擦的估计以及初始塌陷的物理尺寸。在将该模型应用于 Taranaki BAF 之前，必须通过模拟一系列过去的塌陷事件来校准输入参数。通过使用 AD 1860 和 AD 1755 场景，可以很好地约束初始塌陷体积，并且可以通过迭代方法根据先前的跳动长度来评估内部和基础摩擦角。因此，确定了一系列可能的输入参数，以在当今地形下产生一系列可能被淹没的区域。将来自均匀分布范围的 10 个预测组合起来，创建未来 BAF 事件发生淹没的相对概率图。这些结果被合并在 GIS 包中，以生成与用户指定的危险阈值相关的危险区域。使用这些输入参数约束，针对这种规模和类型的事件的未来灾害预测还可以考虑未来喷发或崩塌事件后山顶和地形配置的变化。
Numerical models for simulation of mass flows are typically focussed upon accurately predicting the paths, travel times and inundation from a single flow or collapse event. When considering catchment-based hazards from a volcano, this is complicated by often being faced with several possible scenarios. Over the last 800 years at Mt. Taranaki/Egmont, a number of dome growth and collapse events have resulted in the genesis and emplacement of block-and-ash flows (BAFs). Each BAF was directed northwestward by a breach in the crater rim. The latest dome collapse events in the AD 1880s and AD 1755 inundated the northwestern flank and had run-out lengths 10 km from source. Future activity of this type could have a devastating effect on the Taranaki region’s communities, infrastructure and economy. Hazard planning has involved constructing volcanic hazard maps based upon the areas inundated by past volcanic flows, with little consideration of present-day topography. Here, a numerical geophysical mass flow modelling approach is used to forecast the hazards of future comparable BAF events on NW Mt. Taranaki. The Titan2D programme encompasses a “shallow water”, continuum solution-based, granular flow model. Flow mechanical properties needed for this approach include estimates of internal and basal friction as well as the physical dimensions of the initial collapse. Before this model can be applied to Taranaki BAFs, the input parameters must be calibrated by simulating a range of past collapse events. By using AD 1860 and AD 1755 scenarios, initial collapse volumes can be well constrained and internal and basal friction angles can be evaluated through an iterative approach from previous run-out lengths. A range of possible input parameters was, therefore, determined to produce a suite of potentially inundated areas under present-day terrain. A suite of 10 forecasts from a uniformly distributed range were combined to create a map of relative probabilities of inundation by future BAF events. These results were combined in a GIS package to produce hazard zones related to user-specified hazard thresholds. Using these input parameter constraints, future hazard forecasts for this scale and type of event can also take into account changing summit and topographic configurations following future eruptive or collapse events.