[S-VC33] Monitoring and assessment of volcanic activities

[SVC33-P03] “Pre-eruptive Geodetic Observations of the 2020 Taal Volcano Eruption”

*Lincoln Paul Alcantara Olayta^1,3, Yo Fukushima^2,1, Augusto Ronald Pigtain³ (1.Graduate School of Science, Tohoku University, 2.International Research Institute of Disaster Science (IRIDeS), Tohoku University, Tohoku, Japan, 3.Philippine Institute of Volcanology & Seismology (PHIVOLCS), Department of Science & Technology, Philippines)

Keywords:Volcanology, Active Volcano, Geodesy, InSAR, Volcano Monitoring

Identifying ground deformation signals preceding an eruption is necessary to improve eruption forecasting capability. In January 12, 2020, Taal Volcano erupted after 43 years of repose period. Around 259,000 people were affected and economic losses worth PHP 3.016 billion were reported. From 2016 until 2018, continuous GNSS (cGNSS) observed slight long-term deflation on Taal volcano island (TVI). In the period of March 2019 to January 10, 2020, cGNSS observations indicated outward displacements of ~40 mm/yr for caldera sites, which are located approximately ~5km away from the eruption center, and ~55mm/yr for the TVI sites located less than ~2km from eruption center. Quarterly precise leveling surveys done on TVI in 2019 yielded approximately ~20mm uplift on all sides of the island. Analysis of InSAR time-series using Sentinel-1 ascending & descending views for the period of January 2019 to December 2019 also shows an outward horizontal displacement of ~10cm/yr & positive vertical displacement of around ~5cm/yr on the caldera region. ALOS-2 differential interferogram for January-May, and July-November 2019 also shows around ~5cm outward horizontal displacement in caldera region. We jointly invert the surface displacements of InSAR & GNSS using the 3D mixed boundary element method to determine the most probable depth & geometry of the pressure source. These observations are important in creating a more robust eruption forecasting guide in the case of future volcanic crises for Taal volcano.