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Characterizing Unrest at the Chiles-Cerro Negro Volcanic Complex Using Time-Lapse Gravity Data

Antonina Calahorrano-Di Patre1, Josué Salgado2, Pedro Espín Bedón3, Marco Córdova2, Patricia Mothes2, Maurizio Battaglia1,4

  • Affiliations: 1Department of Earth Sciences, Sapienza University of Rome, Italy; 2IG-EPN, Escuela Politécnica Nacional, Quito, Ecuador; 3Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, UK; 4Volcano Disaster Assistance Program, USGS, CA, USA 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 46

  • Programme No: 2.3.32

  • Theme 2 > Session 3

Abstract

The Chiles-Cerro Negro Volcanic Complex, located on the Ecuador-Colombia border, has exhibited unrest since early 2022. Observed phenomena include 8 cm of uplift near the Chiles edifice, seismic swarms, and mild superficial changes in thermal springs. Nearby, the Potrerillos caldera (10 km south) has shown significant ground deformation, with uplift reaching 60 mm/year. To investigate these activities, gravity monitoring began in June 2022. Surveys covered six sites on Chiles' southern flank and five near Potrerillos. Between July and October 2022, gravity measurements at Chiles indicated a 65 µGal decrease, followed by an equivalent increase by April 2023. After April, gravity changes near Chiles stabilized, while Potrerillos' sites showed a continuous gravity increase reaching up to 45 µGal, alongside ongoing uplift through November 2024. Preliminary results from inversion of geodetic datasets show evidence for two different sources of mass change: a loss of more than 3x1011 kg occurred in Chiles' southern flank between July and October 2022, followed by a similar mass increase in the following months. Additionally, a continuous mass gain 10 to 15 km below Potrerillos Caldera was modelled, with a maximum increase of 7x1012 kg between July 2022 and November 2024. Two potential scenarios explain these observations: (1) a single magmatic source near Potrerillos driving fluid migration towards Chiles along fault systems, resembling the 2014 unrest, or (2) two independent sources of mass change beneath Chiles and Potrerillos. By analyzing gravity data, we aim to identify the most likely scenario and its implications for volcanic activity forecasting.