Mount Pinatubo – a case study of a multihazard network

The Philippines location on the edge of the Pacific makes it a nexus for tectonic and climatic hazards and a real-world example of the possible complexities surrounding multi-hazard assessment, risk management and governance. This inherently multi-hazardous environment and the well documented events over the last few decades provide an opportunity to characterise multi-hazards over temporal and spatial scales beyond those previously considered. We aim to switch from linear considerations of multi-hazard cascades and coincident events to a deeper understanding of more systemic multi-hazard interrelationships (networks). We will review the effects of these spatially and temporarily diverse events on multi-hazard governance and the complexity of managing events that cross institutional and administrative institutions. In this case study we will present the initial mapping of physical and social multihazards associated with Mount Pinatubo from 1990 to the present day. The famous explosive eruption of Mount Pinatubo on the 15th of June 1991 is often referenced as a multihazard event due to the coincident arrival of Typhoon Yunya with the main paroxysmal phase of the eruption. In reality however, this eruption was part of a larger complex network of independent, triggering, compound and change condition hazards that extend over a timeframe of decades. By fully mapping these interactions we hope to stress the lessons that can be learnt from this event and highlight the complexities in managing hazards that cross disciplines and authorities

Reconstructing eruptions at a data limited volcano: A case study at Gede (West Java)

Understanding past eruption dynamics at a volcano is crucial for forecasting the range of possible future eruptions and their associated hazards and risk. In this work we use numerical models to recreate the footprints of pyroclastic density currents (PDCs) and tephra fall from three eruptions at Gede volcano, Indonesia, with the aim of gaining further insight into these past eruptions and identifying suitable eruption source parameters for future hazard and risk assessment. Gede has the largest number of people living within 100 km of any volcano worldwide, and has exhibited recent unrest activity, yet little is known about its eruptive history. For PDCs, we used Titan2D to recreate geological deposits dated at 1.2 and c. 1 kyrs BP. An objective and quantitative multi-criteria method was developed to evaluate the fit of 342 model simulations with field observations. In recreating the field deposits we were able to identify the best fitting values to reconstruct these eruptions. We found that the 1.2 kyrs BP geological deposits could be reproduced with Titan2D using either a dome-collapse or a column-collapse as the triggering mechanism, although a relatively low basal friction angle of 6° would suggest that the PDCs were highly mobile. For the 1 kyrs BP PDC, a column-collapse mechanism and a higher basal friction angle were required to fit the geological deposits. In agreement with previous studies, we found that Titan2D simulations were most sensitive to the basal friction angle parameter. We used Tephra2 to recreate historic observations of tephra dispersed to Jakarta and Gunung Patuha during the last known magmatic eruption of Gede in 1948. In the absence of observable field deposits, or detailed information from the published literature, we stochastically sampled eruption source parameters from wide ranges informed by analogous volcanic systems, allowing us to constrain the eruption dynamics capable of dispersing tephra to the most populous city in Indonesia, Jakarta. Our modelling suggests that the deposition of tephra fall in Jakarta during the November 1948 eruption was a very low probability event, with a < 1% chance of occurrence. Through this work, we show how the reconstruction of past eruptions with numerical models can improve our understanding of past eruption dynamics, when faced with epistemic uncertainty. At Gede volcano, this provides a crucial step towards the reduction of risk to nearby populations through volcanic hazard assessment

Understanding geological hazards to support disaster risk assessment in Indonesia : a report on a collaborative workshop between Resilience Development Initiative and the British Geological Survey

Indonesia encompasses one of the most active tectonic regions on Earth. Geological hazards in the country are a potent threat to a large and vulnerable population. It is therefore important that decisions made by disaster managers are informed by the best available earth science. However, large areas remain unstudied, with limited knowledge of past behaviour impacting understanding of future hazards and risks. To understand the challenges and research opportunities related to natural hazards in Indonesia, the Resilience Development Initiative (RDI) and British Geological Survey (BGS) organised a collaborative workshop over two days in January 2022. The workshop provided an opportunity to bring together key stakeholders in disaster risk science and management in Indonesia. The workshop aimed to discuss and offer a forum to explore research needs in terms of understanding, measuring, mitigating, and modelling geological hazards in Indonesia, with a specific focus on earthquakes, landslides, volcanoes and tsunamis. The main findings from this exercise are summarised below. Fundamental hazard assessment. A common theme across the four geological hazards discussed was the need to improve fundamental hazard assessments. For earthquakes, this involves improving the understanding of crustal faults at the local level and feeding this into national hazard assessment exercises. For landslides, a significant challenge raised was the resolution of susceptibility maps. There is a need to produce local hazard assessments considering local geological and environmental conditions. For volcanoes, the challenges were around understanding how past activity can be used to inform understanding of future hazards. However, participants agreed that it is difficult to understand the potential range of activity at infrequently active volcanoes, making hazard assessment more challenging. The main challenge for tsunamis was understanding the relative importance of various tsunami mechanisms. Earthquake-triggered tsunamis are relatively well understood compared to tsunamis triggered by volcanic eruptions and sediment movement. Baseline geological data. High-quality, up-todate, and complete data are the foundation of the best quality science. It is therefore imperative to collect and manage baseline data. For hazard assessments, there is a clear need for geological data to provide knowledge of past events and understand the possible future activity. Key points were raised around data availability and accessibility, where datasets are stored and who is responsible for storing, maintaining, and sharing data. An important first step to improving knowledge of hazards is to first determine how much data exists and where there are data gaps that can be filled through collaborative research. Collaboration and interdisciplinary working. Disaster Risk Reduction (DRR) challenges require a holistic approach to hazard research and management. Common across all hazards is the need to work across different groups, from researchers to stakeholders and local communities, and across disciplines of science and education, in cluding geology, engineering, sociology, and psychology, among others. Collaboration in every aspect of geological hazard monitoring in Indonesia is crucial among stakeholders. Integration between researchers, government, community and media is needed to close the gap between geological hazards research and community risk perception. Community and culture. Indonesia is a vast country with different communities and cultures. In some communities, there may be a tendency for people to trust local beliefs over official sources such as local scientists or the government. Researchers need to understand and respect the different structures that exist in different communities and find appropriate ways of communicating that are sensitive to these dynamics. Involving communities in the scientific process is a critical way of embedding a safety culture into communities. Transient populations such as displaced peoples, tourists and migrants were identified as particularly vulnerable to geological hazards. Understanding how to reduce the risk to these populations is an important research gap. Communication and engagement. Communication could be improved by involving communities in the scientific process, co-developing outreach and education programs for schools and communities, and through the use of citizen science tools. Additionally, exploring the use of storytelling through traditional art, poems, songs, stories, and films can be a way of raising awareness of hazards and remembering and learning from past events. Institutional responsibilities. The DRR lifecycle from hazard monitoring to crisis response requires precise coordination, collaboration, and division of responsibilities. Making progress on hazard science requires an understanding of institutional roles and responsibilities, and clarity on mandates and relationships between different government organisations and research institutions

Multiparametric quantification of volcanic hazards for eruption forecasting and communication

When a volcano enters a period of unrest it is necessary to assess the threat an eruption will pose. This requires the integration of multiparametric data sets. I present two examples of how different data sets with different levels of uncertainty can be combined to better constrain volcanic hazards, and also how well this information is currently being communicated. Firstly, I develop a new database of plinian eruption characteristics and use it to inform a Bayesian Belief Network that calculates the probability of an eruption becoming plinian in style. I show that the presence of an excess gas phase is one of the key factors. Secondly, I integrate geologic field studies with pyroclastic flow and ash fall modeling to improve hazard assessment at Gede volcano, Indonesia. I use this new set of data to produce an event tree for future activity at Gede. Finally, I perform an analysis of the issuance of volcano alert levels worldwide. I find that current success rates of alert issuance are low and suggest that increasing monitoring networks to an optimal level is likely to improve this.​Doctor of Philosophy (ASE

Forewarned is forearmed: understanding multihazard risk assessment methods for disaster risk reduction and for increasing disaster preparedness

Recent years have demonstrated that changing climate is likely to increase the frequency and impacts of complex multihazard events. There is therefore a pressing need to develop methodologies to comprehensively assess the interactions between hazard, exposure and vulnerability that create multihazard risk assessments. Due to the character of many natural hazard events and the paucity of data in inventories, purely quantitative (statistically driven) methods can be challenging to support consequently many multihazard risk approaches have been more qualitative in nature. We present an overview of a new open-source python toolbox that can generate a compounding multi-hazard risk assessment at national scale in a semi-quantitative manner. The toolbox works by: 1) Creating an index value to allow for the combination of hazard footprints and impacts data for: Flood, Earthquake, Landslide and Volcanic eruptions, 2) Identifying the factors that affect the exposure and vulnerability of buildings to these specific hazards, 3) Calculating of the vulnerability of individual buildings within hazard zones, 4) Applying weights for each building type to express the potential vulnerability of individual buildings to a specific hazard to generate relative single hazard vulnerability maps and then 5) Combining these single hazard ‘relative vulnerability maps’ to generate a multi-hazard vulnerability map which is weighted to reflect single hazard frequencies. This toolbox and the methodologies that support it have been deployed in work the BGS has conducted in Nepal, Tanzania, Brazil and Colombia and is the basis of new collaborations with organizations in the Philippines and Indonesia. We will present an overview of selected use cases to demonstrate how these tools can support DRR and disaster preparedness. Keywords: Geoscience, SE Asia, CCOP, Thematic Sessio

An analysis of the issuance of volcanic alert levels during volcanic crises

Volcano Alert Levels (VALs) are used by volcanologists to quickly and simply inform local populations and government authorities of the level of volcanic unrest and eruption likelihood. Most VALs do not explicitly forecast volcanic activity but, in many instances they play an important role in informing decisions: defining exclusion zones and issuing evacuation alerts. We have performed an analysis on VALs (194 eruptions, 60 volcanoes) to assess how well they reflect unrest before eruption and what other variables might control them. We have also looked at VALs in cases where there was an increase in alert level but no eruption, these we term 'Unrest without eruption' (UwE). We have analyzed our results in the context of eruption and volcano type, instrumentation, eruption recurrence, and the population within 30 km. We found that, 19% of the VALs issued between 1990 and 2013 for events that ended with eruption accurately reflect the hazard before eruption. This increases to ~30% if we only consider eruptions with a VEI ≥ 3. VALs of eruptions from closed-vent volcanoes are more appropriately issued than those from open-vents. These two observations likely reflect the longer and stronger unrest signals associated with large eruptions from closed vents. More appropriate VAL issuance is also found in volcanoes with monitoring networks that are moderately-well equipped (3-4 seismometers, GPS and gas monitoring). There is also a better correlation between VALs and eruptions with higher population density. We see over time (1990 to 2013) that there was an increase in the proportion of `UwE’ alerts to other alerts, suggesting increasing willingness to use VALs well before an eruption is certain. The number of accurate VALs increases from 19% to 55% if we consider all UwE alerts to be appropriate. This higher `success’ rate for all alerts (with or without eruption) is improving over time, but still not optimal. We suggest that the low global accuracy of the issuance of VALs could be improved by having more monitoring networks equipped to a medium level, but also by using probabilistic hazard management during volcanic crisis.NRF (Natl Research Foundation, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)Published versio