Researches:
Article title: Analysis of the 2020 Taal Volcano tephra fall deposits from crowdsourced information and field data
Authors: M. I. R. Balangue-Tarriela, A. M. F. Lagmay, D. M. Sarmiento, J. Vasquez, M. C. Baldago, R. Ybañez, A. A. Ybañez,J. R. Trinidad, S. Thivet, L. Gurioli, B. Van Wyk de Vries, M. Aurelio, D. J. Rafael, A. Bermas, J. A. Escudero
Publication title: Bulletin of Volcanology 84(3), March 2022
Abstract:
After 43 years of dormancy, Taal Volcano violently erupted in January 2020 forming a towering eruption plume. The fall deposits covered an area of 8605 km2, which includes Metro Manila of the National Capital Region of the Philippines. The tephra fall caused damage to crops, traffic congestion, roof collapse, and changes in air quality in the affected areas. In a tropical region where heavy rains are frequent, immediate collection of data is crucial in order to preserve the tephra fall deposit record, which is readily washed away by surface water runoff and prevailing winds. Crowdsourcing, field surveys, and laboratory analysis of the tephra fall deposits were conducted to document and characterize the tephra fall deposits of the 2020 Taal Volcano eruption and their impacts. Results show that the tephra fall deposit thins downwind exponentially with a thickness half distance of about 1.40 km and 9.49 km for the proximal and distal exponential segments, respectively. The total calculated volume of erupted fallout deposit is 0.057 km3, 0.042 km3, or 0.090 km3 using the exponential, power-law, and Weibull models, respectively, and all translate to a VEI of 3. However, using a probabilistic approach (Weibull method) with 90% confidence interval, the volume estimate is as high as 0.097 km3. With the addition of the base surge deposits amounting to 0.019 km3, the volume translates to a VEI of 4, consistent with the classification for the observed height and umbrella radius of the 2020 main eruption plume. VEI 4 is also consistent with the calculated median eruption plume height of 17.8 km and sub-plinian classification based on combined analysis of isopleth and isopach data. Phreatomagmatic activity originated from a vent located in Taal Volcano's Main Crater Lake (MCL), which contained 42 million m3 of water. This eruptive style is further supported by the characteristics of the ash grain components of the distal 12 January 2020 tephra fall deposits, consisting dominantly of andesitic vitric fragments (83-90%). Other components of the fall deposits are lithic (7-11%) and crystal (less than 6%) grains. Further textural and geochemical analysis of these tephra fall deposits contributes to better understand the volcanic processes that occurred at Taal Volcano, one of the 16 Decade Volcanoes identified by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) because of its destructive nature and proximity to densely populated areas. The crowdsourcing initiative provided a significant portion of the data used for this study while at the same time educating and empowering the community to build resilience. Supplementary information: The online version contains supplementary material available at 10.1007/s00445-022-01534-y.
Full text available upon request to the author/slink https://tinyurl.com/4a972p8u
Article title: Imaging ground surface deformations in post-disaster settings via small UAVs
Authors: Richard L. Ybañez, Audrei Anne B. Ybañez, Alfredo Mahar Francisco A. Lagmay, and Mario A. Aurelio
Publication title: Geoscience Letters 8(1), December 2021
Abstract:
Small unmanned aerial vehicles have been seeing increased deployment in field surveys in recent years. Their portability, maneuverability, and high-resolution imaging are useful in mapping surface features that satellite- and plane-mounted imaging systems could not access. In this study, we develop and apply a work plan for implementing UAV surveys in post-disaster settings to optimize the flights for the needs of the scientific team and first responders. Three disasters caused by geophysical hazards and their associated surface deformation impacts were studied implementing this workplan and were optimized based on the target features and environmental conditions. An earthquake that caused lateral spreading and damaged houses and roads near riverine areas were observed in drone images to have lengths of up to 40 m and vertical displacements of 60 cm. Drone surveys captured 2D aerial raster images and 3D point clouds leading to the preservation of these features in soft-sedimentary ground which were found to be tiled over after only 3 months. The point cloud provided a stored 3D environment where further analysis of the mechanisms leading to these fissures is possible. In another earthquake-devastated locale, areas hypothesized to contain the suspected source fault zone necessitated low-altitude UAV imaging below the treeline capturing Riedel shears with centimetric accuracy that supported the existence of extensional surface deformation due to fault movement. In the aftermath of a phreatomagmatic eruption and the formation of sub-metric fissures in nearby towns, high-altitude flights allowed for the identification of the location and dominant NE–SW trend of these fissures suggesting horst-and-graben structures. The work plan implemented and refined during these deployments will prove useful in surveying other post-disaster settings around the world, optimizing data collection while minimizing risk to the drone and the drone operators.
Full text link https://tinyurl.com/y69jysr8
Article title: Hazardous base surges of Taal's 2020 eruption
Authors: A. M. F. Lagmay, M. I. R. Balangue‑Tarriela, M. Aurelio, R. Ybanez, A. Bonus‑Ybanez, J. Sulapas, C. Baldago, D. M. Sarmiento, H. Cabria, R. Rodolfo, D. J. Rafael, J. R. Trinidad, E. Obille Jr. & N. Rosell II
Publication title: Scientific Reports 11(15703), August 2021
Abstract:
After 43 years of repose, Taal Volcano erupted on 12 January 2020 forming hazardous base surges. Using field, remote sensing (i.e. UAV and LiDAR), and numerical methods, we gathered primary data to generate well-constrained observed information on dune bedform characteristics, impact dynamic pressures and velocities of base surges. This is to advance our knowledge on this type of hazard to understand and evaluate its consequences and risks. The dilute and wet surges traveled at 50-60 ms −1 near the crater rim and decelerated before making impact on coastal communities with dynamic pressures of at least 1.7 kPa. The base surges killed more than a thousand livestock in the southeast of Taal Volcano Island, and then traveled another ~ 600 m offshore. This work is a rare document of a complete, fresh, and practically undisturbed base surge deposit, important in the study of dune deposits formed by volcanic and other processes on Earth and other planets.
Full text link https://tinyurl.com/ym592aje
Article title: Anatomy of the Naga City Landslide and Comparison With Historical Debris Avalanches and Analog Models
Authors: Alfredo Mahar Lagmay, Carmille Marie Escape, Audrei Anne Bonus Ybañez, John Kenneth Suarez, Genaro Cuaresma
Publication title: Frontiers in Earth Science 8, August 2020
Abstract:
Debris avalanches pose some of the most destructive geologic hazards that threaten both urban and rural populations around the world. On 20 September 2018, villages in Naga City, Cebu, Philippines, were devastated by a landslide that claimed 78 lives with 6 missing, joining other catastrophic landslides in the country like the 1628 Iriga and the 2006 Guinsaugon debris avalanches. Understanding the mechanism of these gargantuan landslides and their correct nomenclature are useful for hazard prevention and mitigation. In this study, we compare the deposit characteristics of the Naga City landslide with analog models and well-known historical debris avalanche events/deposits in the Philippines to understand factors that led to the landslide disaster in Naga City. Physical characteristics obtained from aerial and satellite imagery, ground surveys, recorded footage, borehole data, and lithologic maps provided a detailed dataset for analyzing the conditions that led to the mass movement and the observed characteristics of the Naga landslide deposits. Comparison with analog models of hummock formation and the description of historical debris avalanche deposits show striking similarities, which were used to demonstrate that the Naga landslide was a Rockslide-Debris Avalanche. The equations of Corominas (1996) and Dade and Huppert (1998) for long-runout rockfalls support this analysis. The Naga landslide event is an example of a well-documented debris avalanche, complete with all the characteristics of this type of rapid mass movement. It is consistent with the descriptions found in the literature with respect to its deposit features and mechanical behavior as defined by laboratory models and empirically-derived equations. This study helps us understand historical and future long-runout debris avalanches in order for scientists and authorities to find ways to save lives. Unfortunately, there was a lack of appropriate hazards assessment on the site, which had warnings in the form of the development of fractures at the headscarp of the landslide, a month prior to the disaster.
Full text link https://tinyurl.com/ycx87jak
Article title: Flood Susceptibility Assessment of Mt. Makiling, Philippines Using Two-Dimensional Meteorological and Hydrological Modelling
Authors: Richard L. Ybañez, Bernard Alan B. Racoma, Audrei Anne B. Ybañez, and Maria Ines Rosana D. Balangue-Tarriela
Publication title: Philippine Journal of Science 147(3):463-471, September 2018
Abstract:
In a data-poor, hazard-prone country like the Philippines, interpolating distant data points and computer modelling have become the go-to methods for determining the hazards that may affect an area. The absence of monitoring stations and gauges necessitates the application of modelling techniques to build on the little data available and generate reliable hazard maps. In this study-the devastating Sep 2009 Tropical Cyclone Ketsana (local name: Ondoy) event, its atmospheric characteristics, and its effects near Mt. Makiling, Laguna-is analyzed utilizing two modelling software: the Weather Research and Forecasting (WRF) model to assess the amount of rainfall, and FLO-2D to map the flood hazard areas around the volcano using the output of the WRF. A lone meteorological observation station on Mt. Makiling provided rainfall data for comparison with the results of the meteorological and hydrological models. The WRF model yielded a mean rainfall amount in the study area of 129.92 mm over 24 h for the storm against the observed rainfall amount for the same duration at 182.3 mm from the meteorological station. The flood model using the WRF data yielded minimal inundated areas, while the flood model of the observed rainfall data showed several low-lying urban areas inundated by up to 1.5 m of floodwaters. Comparison with flood data collected by responding agencies and groups after the event shows good correlation of affected areas and flood heights, with discrepancies being attributed to the swelling of Laguna de Bay because of excess runoff from other surrounding provinces-a factor that the models could not consider. Despite this, the WRF model generated from global atmospheric data and the flood model using the WRF product appears as a feasible substitute in the absence of on-site observation points and monitoring stations.
Full text link https://tinyurl.com/4cezrs5k
Article title: Landslide and debris flow susceptibility mapping of Leyte Province, Philippines using remote sensing, numerical modelling, and GIS
Authors: RN Eco, DT Aquino, AMF Lagmay, I Alejandrino, AA Bonus, CM Escape, R Felix, PK Ferrer, RC Gacusan, J Galang, F Llanes, PK Luzon, KR Montalbo, IJ Ortiz, M Rabonza, V Realino, JM Sabado, JJ Sulapas, H Ariola, J Obrique, C Quina, MK Alemania, M Magcamit, S Salvosa, and NL Timba
Publication title: Journal of the Philippine Geoscience and Remote Sensing Society 1(1), September 2015
Abstract:
When Super Typhoon Haiyan struck the Philippines in November 2013, the province of Leyte was among the most heavily damaged. Detailed hazard susceptibility maps for Leyte–including storm surge, flood,and landslide hazard maps–that could have mitigated the damage by providing crucial information on possible hazards and their extent were not available to communities prior to Haiyan. To aid future disaster prevention and mitigation efforts, we produce landslide susceptibility maps downscaled to the community-level for the entire Leyte province. We integrate remote sensing, numerical modelling, and GIS tools to maximize the use of a high-resolution digital terrain model of the province. The detailed landslide susceptibility maps are useful for identifying safe and unsafe areas for rehabilitation and reconstruction efforts for Haiyan devastated areas,as well as for community disaster planning and preparedness efforts
Full text available upon request to the author/s