The unrest of the San Miguel volcano (El Salvador, Central America): installation of the monitoring network and observed volcano-tectonic ground deformation

Abstract

Abstract. On 29 December 2013, the Chaparrastique volcano in El Salvador, close to the town of San Miguel, erupted suddenly with explosive force, forming a column more than 9 km high and projecting ballistic projectiles as far as 3 km away. Pyroclastic density currents flowed to the north-northwest side of the volcano, while tephras were dispersed northwest and north-northeast. This sudden eruption prompted the local Ministry of Environment to request cooperation with Italian scientists in order to improve the monitoring of the volcano during this unrest. A joint force, made up of an Italian team from the Istituto Nazionale di Geofisica e Vulcanologia and a local team from the Ministerio de Medio Ambiente y Recursos Naturales, was organized to enhance the volcanological, geophysical and geochemical monitoring system to study the evolution of the phenomenon during the crisis. The joint team quickly installed a multiparametric mobile network comprising seismic, geodetic and geochemical sensors (designed to cover all the volcano flanks from the lowest to the highest possible altitudes) and a thermal camera. To simplify the logistics for a rapid installation and for security reasons, some sensors were colocated into multiparametric stations. Here, we describe the prompt design and installation of the geodetic monitoring network, the processing and results. The installation of a new ground deformation network can be considered an important result by itself, while the detection of some crucial deforming areas is very significant information, useful for dealing with future threats and for further studies on this poorly monitored volcano. IntroductionThe San Miguel volcano, also known as Chaparrastique, is a symmetrical stratovolcano, which reaches 2130 m a.s.l. (above sea level). Its summit crater measures 800 m in diameter and 340 m in depth. The El Pacayal volcano (currently inactive) is located 6 km NW from the San Miguel edifice (Fig. 1).Geographically, it is located in the department of San Miguel, in the eastern part of El Salvador, at coordinates 13.43143 • N and 88.271468 • W. The entire edifice belongs to the municipalities of San Miguel, Quelepa, Moncagua, Chinameca, San Jorge, San Rafael Oriente and El Tránsito.Geologically, it belongs to the quaternary period (probably with an age of about 50 000 years) and is mainly made up of basaltic and andesitic rocks. However, the stratigraphy of the volcano is intercalated with Plinian acid deposits (dacite and rhyodacite) of the El Pacayal volcano. Lava flows and mafic scoria emitted through lateral fissures (Escobar et al., 2004) are evident on the flanks of the volcano; the occurrence of such lateral eruptions increases the hazard for the numerPublished by Copernicus Publications on behalf of the European Geosciences Union.

Geochemical characterization of volcanic gas emissions at Santa Ana and San Miguel volcanoes, El Salvador, using remote-sensing and in situ measurements

“…It rises 2,310 m a.s.l near and is located at about 11 km distance from the municipalities of San Miguel, El Tránsito, San Rafael Oriente, and San Jorge. It lies on the eastern section of the Central Graben of the country, which is crossed by the regional NW-SE fault system (Bonforte et al, 2016). Its northern flank extends to the San Esteban river, while its western flank is truncated against the Ojo de Agua (Cerro El Limbo) and Chinameca (Cerro El Pacayal) volcanoes (Chesner et al, 2004).…”

Reconstruction of the 29th December 2013 eruption of San Miguel volcano, El Salvador, using video, photographs, and pyroclastic deposits

“…Lahars have been generated on the flanks of the volcano. The 2013 eruption spurred interest in the volcano [Scarlato et al 2016;Jiménez et al 2018;2020] and instigated international collaborations to improve the seismic, geodetic, and geochemical monitoring network around the volcano [Bonforte et al 2016].…”