Browsing by Author "Jenkins SF"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    A new perspective on eruption data completeness: insights from the First Recorded EruptionS in the Holocene (FRESH) database
    (Elsevier BV, 2022-11) Burgos V; Jenkins SF; Bebbington M; Newhall C; Taisne B
    Identifying the most complete (best recorded) portion of an eruption record is essential before estimating eruption recurrence and probability. This is typically achieved by plotting cumulative eruptions through time. Here, we evaluate eruption data completeness from a new perspective, by compiling the first dated Holocene eruption from each volcano in the Volcanoes of the World (VOTW) database (i.e., First Recorded EruptionS in the Holocene (FRESH)). In our first analysis, we compared the subregional distribution of FRESH with time using Kolmogorov-Smirnov (K[sbnd]S) test. We found that the eruption record was best categorised into 31 regions containing subregions with similar degrees of completeness. This opened the way to define new Relative Completeness Date(s) (RCD) as a function of eruption size, volcanic characteristics, and region, by identifying multiple points in the record where the root-mean-square (RMS) level changes abruptly, corresponding to a gap, a decrease or increase in the FRESH rate. Regional RCDs in the Common Era (CE) range from as recently as 1964 CE in the Indian Ocean (southern) to 200 CE in Middle East and Western Indian Ocean. In contrast, some regions like Kamchatka and Mainland Asia have near-constant rates of FRESH over the last 12,000 years, making RCDs impossible to assign. We present and make available our FRESH database, and describe and implement an automatic approach to detect RCDs across our newly defined volcanic regions. We suggest that the different degrees of completeness observed at a regional scale can be explained by: socio-historical events, access to geological studies, submarine volcanism, and/or remoteness. The FRESH database, together with the new regions and proposed RCDs can be used in future studies to estimate eruption probabilities at volcanoes without Holocene records and identify which subregions are most likely to produce a FRESH in the future.
  • Thumbnail Image
    Item
    Identifying analogues for data-limited volcanoes using hierarchical clustering and expert knowledge: a case study of Melimoyu (Chile)
    (Frontiers Media S.A., 2023-05-24) Burgos V; Jenkins SF; Bono Troncoso L; Perales Moya CV; Bebbington M; Newhall C; Amigo A; Prada Alonso J; Taisne B; Fournier N
    Determining the eruption frequency-Magnitude (f-M) relationship for data-limited volcanoes is challenging since it requires a comprehensive eruption record of the past eruptive activity. This is the case for Melimoyu, a long-dormant and data-limited volcano in the Southern Volcanic Zone (SVZ) in Chile with only two confirmed Holocene eruptions (VEI 5). To supplement the eruption records, we identified analogue volcanoes for Melimoyu (i.e., volcanoes that behave similarly and are identified through shared characteristics) using a quantitative and objective approach. Firstly, we compiled a global database containing 181 variables describing the eruptive history, tectonic setting, rock composition, and morphology of 1,428 volcanoes. This database was filtered primarily based on data availability into an input dataset comprising 37 numerical variables for 438 subduction zone volcanoes. Then, we applied Agglomerative Nesting, a bottom-up hierarchical clustering algorithm on three datasets derived from the input dataset: 1) raw data, 2) output from a Principal Component Analysis, and 3) weighted data tuned to minimise the dispersion in the absolute probability per VEI. Lastly, we identified the best set of analogues by analysing the dispersion in the absolute probability per VEI and applying a set of criteria deemed important by the local geological service, SERNAGEOMIN, and VB. Our analysis shows that the raw data generate a low dispersion and the highest number of analogues (n = 20). More than half of these analogues are in the SVZ, suggesting that the tectonic setting plays a key role in the clustering analysis. The eruption f-M relationship modelled from the analogue’s eruption data shows that if Melimoyu has an eruption, there is a 49% probability (50th percentile) of it being VEI≥4. Meanwhile, the annual absolute probability of a VEI≤1, VEI 2, VEI 3, VEI 4, and VEI≥5 eruption at Melimoyu is 4.82 × 10−4, 1.2 × 10−3, 1.45 × 10−4, 9.77 × 10−4, and 8.3 × 10−4 (50th percentile), respectively. Our work shows the importance of using numerical variables to capture the variability across volcanoes and combining quantitative approaches with expert knowledge to assess the suitability of potential analogues. Additionally, this approach allows identifying groups of analogues and can be easily applied to other cases using numerical variables from the global database. Future work will use the analogues to populate an event tree and define eruption source parameters for modelling volcanic hazards at Melimoyu.
  • Thumbnail Image
    Item
    Intra-Eruption Forecasting Using Analogue Volcano and Eruption Sets
    (John Wiley and Sons, Inc on behalf of the American Geophysical Union, 2022-06-23) Bebbington MS; Jenkins SF
    Forecasting the likely style and chronology of activity within an eruption is a complex issue that has received far less attention than forecasting the onset and/or the magnitude. By developing a global data set of coded phases (discrete styles of activity within previous eruptions), we can model the resulting data using a semi-Markov chain. Given enough data, we were able to examine the question of whether analogue-based strategies for subsetting the data can improve forecasting performance of phase chronology and style within ongoing eruptions. This work required inclusion of a “null analogue” element to ensure no surprises, that is, phase transitions or durations that were not in the data set and hence cannot be predicted. We have significantly expanded, and made available, our curated data set on eruption phases, which now contains 2670 eruptions (6871 phases), of which 56% are multi-phase. This increases the data set by 283% and includes 95% of Holocene eruptions with text descriptions. We find that, with the notable exception of shields, limiting the analogue set on the basis of volcano morphology and/or composition is not significantly more informative than using the entire data set. Dynamically adjusting the data limits by eliminating eruptions without the observed phase as the eruption progresses provided little benefit, although subsetting on the basis of VEI may have some utility. At the individual volcano level, non-analogue models can outperform the entire data set, if the target volcano has relatively unique behavior and/or a large enough record of phased eruptions.
  • Thumbnail Image
    Item
    Tephra fall impacts to buildings: the 2017–2018 Manaro Voui eruption, Vanuatu
    (Frontiers Media S.A., 2024-08-15) Jenkins SF; McSporran A; Wilson TM; Stewart C; Leonard G; Cevuard S; Garaebiti E; Varley N
    Building damage from tephra falls can have a substantial impact on exposed communities around erupting volcanoes. There are limited empirical studies of tephra fall impacts on buildings, with none on tephra falls impacting traditional thatched timber buildings, despite their prevalence across South Pacific island nations and parts of Asia. The 2017/2018 explosive eruption of Manaro Voui, Ambae Island, Vanuatu, resulted in damage to traditional (thatched timber), non-traditional (masonry), and hybrid buildings from tephra falls in March/April and July 2018. Field and photographic surveys were conducted across three separate field studies with building characteristics and damage recorded for a total of 589 buildings. Buildings were classified using a damage state framework customised for this study. Overall, increasing tephra thicknesses were related to increasing severity of building damage, corroborating previous damage surveys and vulnerability estimates. Traditional buildings were found to be less resistant to tephra loading than non-traditional buildings, although there was variation in resistance within each building type. For example, some traditional buildings collapsed under ∼40 mm thickness while others sustained no damage when exposed to >200 mm. We attribute this to differences in the pre-eruption condition of the building and the implementation of mitigation strategies. Mitigation strategies included covering thatched roofs with tarpaulins, which helped shed tephra and consequently reduced loading, and providing an internal prop to the main roof beam, which aided structural resistance. As is typical of post-event building damage surveys, we had limited time and access to the exposed communities, and we note the limitations this had for our findings. Our results contribute to the limited empirical data available for tephra fall building damage and can be used to calibrate existing fragility functions, improving our evidence base for forecasting future impacts for similar construction types globally.
  • Thumbnail Image
    Item
    What is the probability of unexpected eruptions from potentially active volcanoes or regions?
    (Springer Nature Switzerland AG on behalf of the International Association of Volcanology and Chemistry of the Earth's Interior, 2022-11) Burgos V; Jenkins SF; Bebbington M; Newhall C; Taisne B; Sandri L
    Since the start of the twentieth century, 101 potentially active volcanoes have produced their first Holocene eruption, as recorded in the volcanoes of the world (VOTW) database. The reactivation of potentially active volcanoes is often a surprise, since they tend to be less well-studied and unmonitored. The first step towards preparing for these unexpected eruptions is to establish how often potentially active volcanoes have erupted in the past. Here, we use our previously developed FRESH (First Recorded EruptionS in the Holocene) database to estimate the past regional Average Recurrence Interval (ARI) of these unexpected events. Within the most complete portions of the FRESH database, a FRESH (i.e., the first recorded eruption from a potentially active volcano) has occurred as frequently as every ~ 7 years in the Pacific Ocean region (~ 50 years of relatively complete record) and ~ 8 years in Izu, Volcano, and the Mariana Islands region (~ 150 years of relatively complete record). We use the regional frequency to estimate the annual probability of a FRESH at individual potentially active volcanoes in selected regions of Asia–Pacific, which ranged from 0.003 for Izu, Volcano, and Mariana Islands to 1.35 × 10−5 for Luzon. Population exposure around potentially active volcanoes showed that at volcanoes such as Kendeng (Indonesia) and Laguna Caldera (Philippines), more than 30 million people reside within 100 km of the summit. With this work, we hope to establish how often potentially active volcanoes erupt, while identifying which regions and which potentially active volcanoes may require more attention.