Browsing by Author "Sortino, Francesco"

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Disruptions in the hydrothermal water geochemistry inside Misti volcano in coincidence with the 8.4 Mw earthquake of June 23rd, 2001, in southern Peru
    (Instituto Geofísico del Perú, 2001) Cruz, Vicentina; Finizola, Anthony; Macedo Sánchez, Orlando Efraín; Sortino, Francesco
    Misti volcano (16°18'S, 71°24'W and 5822 in elevation) is located 17 km from Arequipa (-800000 inhabitants). It is characterized by two concentric summit craters. The youngest one hold lava dome, 130m wide, with fumarolic activity and temperature higuer than 200°C, geochemical techniques turn out to be very effective for the monitoring of active volcanoes. The ascent of a magmatic gases and their interactions with aquifers induce changes in the chemical composition and physical properties of the waters that can be sampled at the surface.The geochemical monitoring of the Misti volcano began in 1998 with a systematic sampling of the hot spring of "Charcani V", located to 6 Km of the active crater at 2960 meters in elevation.
    Palabras clave:Misti volcanoSeismicityGeochemistry
  • Thumbnail Image
    ItemOpen Access
    Estudio estructural y del sistema hidrotermal del volcán Ubinas por métodos geofísicos y geoquímicos
    (Sociedad Geológica del Perú, 2002) Macedo Sánchez, Orlando Efraín; Gonzales Zuñiga, Katherine; Finizola, Anthony; Métaxian, Jean-Philippe; Fournier, Nicolas; Sortino, Francesco
    El volcán Ubinas (16° 22’ S, 70° 54’ W; 5672 m.s.n.m.) ubicado en el sur del Perú y dentro de la ZVC o Zona Volcánica Central de los Andes (Fig. 1), es considerado como el más activo del Perú, con hasta 23 erupciones menores registradas históricamente en los últimos 450 años. Estudios geológicos recientemente realizados sobre este volcán han puesto en evidencia su condición de peligro potencial (Rivera, 1997; Rivera et al., 1997). Poco se conoce, sin embargo, acerca de su estructura interna. Este trabajo muestra los resultados de la aplicación de diferentes métodos geofísicos, geoquímicos, de la realización de mediciones de temperatura del suelo, y observaciones detalladas del interior del cráter activo, realizadas en el volcán Ubinas entre 1997 y 1999. Tales resultados han permitido proponer un modelo de estructura y de circulación de fluidos propio a este volcán andesítico. Se ha efectuado principalmente un amplio trabajo de investigación por potencial espontáneo (PE) con mediciones a lo largo de 9 perfiles radiales que cubren todo el edificio y con mediciones detalladas del PE sobre el piso de la caldera. Asimismo, se ha efectuado un breve monitoreo de la actividad sísmica instalándose sismómetros sobre la parte superior del cono volcánico, un análisis de la concentración de CO2 en los gases del suelo tanto sobre el edificio como al interior de la caldera, detalladas mediciones de la temperatura sobre el piso de la caldera, y finalmente, un análisis geoquímico preliminar de aguas termales y frías próximas a la zona del volcán.
    Palabras clave:Volcán UbinasEstudios geofísicosGeología estructural
  • Thumbnail Image
    ItemRestricted
    Fluid circulation and structural discontinuities inside Misti volcano (Peru) inferred from self-potential measurements
    (Elsevier, 2004-08) Finizola, Anthony; Lénat, Jean-François; Macedo Sánchez, Orlando Efraín; Ramos Palomino, Domingo A.; Thouret, Jean-Claude; Sortino, Francesco
    One of the seven potentially active andesite stratovolcanoes in southern Peru, Misti (5822 m), located 17 km northeast and 3.5 km above Arequipa, represents a major threat to the population (∼900,000 inhabitants). Our recent geophysical and geochemical research comprises an extensive self-potential (SP) data set, an audio – magnetotelluric (AMT) profile across the volcano and CO2 concentrations in the soil along a radial profile. The SP survey is the first of its kind in providing a complete mapping of a large andesitic stratovolcano 20 km in diameter. The SP mapping enables us to analyze the SP signature associated with a subduction-related active volcano. The general SP pattern of Misti is similar to that of most volcanoes with a hydrogeologic zone in the lower flanks and a hydrothermal zone in the upper central area. A quasi-systematic relationship exists between SP and elevation. Zones with constant SP/altitude gradients (Ce) are observed in both hydrogeologic (negative Ce) and hydrothermal (positive Ce) zones. Transition zones between the different Ce zones, which form a concentric pattern around the summit, have been interpreted in terms of lateral heterogeneities in the lithology. The highest amplitudes of SP anomalies seem to coincide with highly resistive zones. The hydrothermal system 6 km in diameter, which extends over an area much larger than the summit caldera, may be constrained by an older, concealed collapse caldera. A sealed zone has apparently developed through alteration in the hydrothermal system, blocking the migration of CO2 upward. Significant CO2 emanations are thus observed on the lower flanks but are absent above the hydrothermal zone.
    Palabras clave:Misti volcanoSelf-potentialAudio–magnetotelluric