scholarly journals Statistical eruption forecast for the Chilean Southern Volcanic Zone: typical probabilities of volcanic eruptions as baseline for possibly enhanced activity following the large 2010 Concepción earthquake

2010 ◽  
Vol 10 (10) ◽  
pp. 2093-2108 ◽  
Author(s):  
Y. Dzierma ◽  
H. Wehrmann
Keyword(s):  
Volcanic Eruptions ◽  
Distribution Functions ◽  
Logistic Distribution ◽  
Volcanic Zone ◽  
Southern Volcanic Zone ◽  
Enhanced Activity ◽  
Eruption Probability ◽  
The Individual ◽  
Chilean Southern Volcanic Zone ◽  
Eruption Time Series

Abstract. A probabilistic eruption forecast is provided for ten volcanoes of the Chilean Southern Volcanic Zone (SVZ). Since 70% of the Chilean population lives in this area, the estimation of future eruption likelihood is an important part of hazard assessment. After investigating the completeness and stationarity of the historical eruption time series, the exponential, Weibull, and log-logistic distribution functions are fit to the repose time distributions for the individual volcanoes and the models are evaluated. This procedure has been implemented in two different ways to methodologically compare details in the fitting process. With regard to the probability of at least one VEI ≥ 2 eruption in the next decade, Llaima, Villarrica and Nevados de Chillán are most likely to erupt, while Osorno shows the lowest eruption probability among the volcanoes analysed. In addition to giving a compilation of the statistical eruption forecasts along the historically most active volcanoes of the SVZ, this paper aims to give "typical" eruption probabilities, which may in the future permit to distinguish possibly enhanced activity in the aftermath of the large 2010 Concepción earthquake.

Exploring the shallow geothermal resources in the Chilean Southern Volcanic Zone: Insight from the Liquiñe thermal springs

2020 ◽  
Vol 218 ◽  
pp. 106611
Author(s):  
Linda Daniele ◽  
Matías Taucare ◽  
Benoît Viguier ◽  
Gloria Arancibia ◽  
Diego Aravena ◽  
...  
Keyword(s):  
Thermal Springs ◽  
Volcanic Zone ◽  
Geothermal Resources ◽  
Southern Volcanic Zone ◽  
Chilean Southern Volcanic Zone

Reprocessing, depth conversion and structural restoration of vintage seismic data: New insights into the volcano-tectonic evolution of the Christiana-Santorini-Kolumbo marine volcanic zone

2020 ◽  
Author(s):  
Christian Huebscher ◽  
Jonas Preine
Keyword(s):  
Bronze Age ◽  
Model Building ◽  
Aegean Sea ◽  
Volcanic Eruptions ◽  
Velocity Model ◽  
Rift System ◽  
Volcanic Zone ◽  
Structural Restoration ◽  
Stratigraphic Model ◽  
The Individual

<p>Located on the Hellenic Volcanic Arc, the Christiana-Santorini-Kolumbo (CSK) marine volcanic zone is notorious for its catastrophic volcanic eruptions, earthquakes and tsunamis. Here, not only the largest volcanic eruption in human history, the so-called “Minoan” eruption took place in the Late Bronze age 3600 years ago, but also the largest 20th-century shallow earthquake in Europe of magnitude 7.4 in 1956. Although the region is heavily populated and a fully developed touristic region, the acting tectonic forces are not fully understood to this day aggravating the necessary assessment of geohazards.</p><p>Recent bathymetric and seismic studies revealed that the CSK zone comprises a system of neotectonic horst and graben structures with extended internal faulting that is thought to be the result of the ongoing extension in the southern Aegean. The NE-SW alignment of volcanic edifices within the CSK underlines the tectonic control of volcanism in this area. In this study, we show how advanced reprocessing of selected seismic lines leads to significantly improved seismic images revealing new details of the complex rift system. Moreover, using a unique diffraction-based approach for velocity model building, we perform pre-stack depth migration (PSDM) and present for the first time depth-converted seismic sections from the CSK zone. This allows for the proper estimation of fault angles, sedimentary thicknesses and performing structural restoration in order to reconstruct and measure the amount of extension in the individual rift basins. We revise the previous seismostratigraphic scheme and propose a new correlation between the horst and graben units.</p><p>Structural restoration indicates an extension of approx. 3 km along the Santorini-Anafi basin while PSDM indicates the sedimentary strata to be of maximum 1500 m thickness. According to the new stratigraphic model, we infer a four-stage evolution of this basin in which early marine deposition, syn-rift deposition, complex infill deposition and neotectonic syn-rift deposition are distinguished. Moreover, we identify negative flower structures within the basin centre indicating the presence of a strike-slip component, which superimposes the dominant NW-SE directed extension. Based on these findings, we are confident that by applying the proposed workflow to the complete regional dataset, the understanding of the relationship between tectonics and volcanism in the CSK zone will be significantly improved, and, consequently, will lead to an improved risk assessment of the central Aegean Sea.</p>

scholarly journals What is the magma storage depth under Osorno Volcano (Southern Volcanic Zone, Chile)?

2020 ◽  
Author(s):  
Tonin Bechon ◽  
Jacqueline Vander Auwera ◽  
Olivier Namur ◽  
Paul Fugmann ◽  
Olivier Bolle ◽  
...  
Keyword(s):  
Continental Crust ◽  
Volcanic Eruptions ◽  
Magma Ascent ◽  
Convergent Margins ◽  
Volcanic Zone ◽  
Moho Interface ◽  
Magmatic Arc ◽  
Magma Chamber Processes ◽  
Southern Volcanic Zone ◽  
Mafic Lavas

<p>The depth at which magma chamber processes take place below magmatic arcs and the parameters controlling them are highly debated. These questions are fundamental for our understanding of the global magma differentiation as well as the formation of the continental crust at convergent margins, but also for evaluating the risks associated with volcanic eruptions.</p><p>In the Central Southern Volcanic Zone (Central-SVZ) of the Chilean Andes, a thin continental crust (30-40 km) and the occurrence of a major fault zone (Linquiñe-Ofqui) likely favor rapid magma ascent. This segment of the arc is as a consequence one of the most active in Chile with several recent eruptions (e.g. Llaima 2009, Cordon Caulle 2011, Calbuco 2015, Villarrica 2015 & 2019). The Central-SVZ is characterized by dominant mafic lavas (basalts, basaltic andesites), few rhyodacitic lavas, a noticeable compositional (Daly) gap in the intermediate compositions (andesites). Noteworthy, amphibole is usually absent, except in a few volcanoes (e.g. Calbuco) or only occurs as microliths in enclaves, which suggests rather low water contents. These observations contrast sharply with the Northern-SVZ where andesitic lavas are dominant and hydrous phases common.</p><p>We focused our research on the eruptive products of Osorno volcano (41°S, CSVZ) located between two volcanoes (Calbuco and Cordon Caulle) which recently showed very explosive eruptions and partly overlies an older Pleistocene eroded volcanic edifice (La Picada). A large series of samples were collected in four units spanning 200 kyr. They define a differentiation trend ranging from tholeiitic basalts to calk-alkaline dacites with a Daly Gap between 58 wt. % and 63 wt. % SiO<sub>2</sub>. Plagioclase and olivine are dominant before the gap while plagioclase and clino- and orthopyroxene dominate afterwards.</p><p>The use of recent thermobarometric models revealed two main storage regions: (1) at the MOHO interface (1-1.2GPa) and (2), at the upper/lower crust interface with rather low pressures (likely ≤0.3 Gpa). While at (1) primary magmas differentiate, (2) is interpreted as the depth of major differentiation and volatile exsolution. Thermodynamic simulations (Gualda et al., 2012; Ghiorso & Gualda, 2015) support these (2) depth estimates and reproduce the main paragenesis by simple fractional crystallization at 0.1-0.2 GPa. Our results may explain the recent seismic unrest below Osorno (from 2015 to 2019) with earthquakes mostly taking place between 0.1-0.3 GPa (4-10km below the summit). We suggest that Osorno is an important target to perform a comprehensive petrological study aiming at characterizing the Central-SVZ magmatic arc and the magmatic storage depths.</p>

scholarly journals Mantle Melting and Magmatic Processes Under La Picada Stratovolcano (CSVZ, Chile)

2019 ◽  
Vol 60 (5) ◽  
pp. 907-944 ◽  
Author(s):  
Jacqueline Vander Auwera ◽  
Olivier Namur ◽  
Adeline Dutrieux ◽  
Camilla Maya Wilkinson ◽  
Morgan Ganerød ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Geochemical Data ◽  
Upper Crust ◽  
Volcanic Zone ◽  
Nazca Plate ◽  
Southern Volcanic Zone ◽  
Magmatic Processes ◽  
Crystal Accumulation ◽  
Primary Magmas ◽  
Differentiation Trend

Abstract Where and how arc magmas are generated and differentiated are still debated and these questions are investigated in the context of part of the Andean arc (Chilean Southern Volcanic Zone) where the continental crust is thin. Results are presented for the La Picada stratovolcano (41°S) that belongs to the Central Southern Volcanic Zone (CSVZ) (38°S–41·5°S, Chile) which results from the subduction of the Nazca plate beneath the western margin of the South American continent. Forty-seven representative samples collected from different units of the volcano define a differentiation trend from basalt to basaltic andesite and dacite (50·9 to 65·6 wt % SiO2). This trend straddles the tholeiitic and calc-alkaline fields and displays a conspicuous compositional Daly Gap between 57·0 and 62·7 wt % SiO2. Interstitial, mostly dacitic, glass pockets extend the trend to 76·0 wt % SiO2. Mineral compositions and geochemical data indicate that differentiation from the basaltic parent magmas to the dacites occurred in the upper crust (∼0·2 GPa) with no sign of an intermediate fractionation stage in the lower crust. However, we have currently no precise constraint on the depth of differentiation from the primary magmas to the basaltic parent magmas. Stalling of the basaltic parent magmas in the upper crust could have been controlled by the occurrence of a major crustal discontinuity, by vapor saturation that induced volatile exsolution resulting in an increase of melt viscosity, or by both processes acting concomitantly. The observed Daly Gap thus results from upper crustal magmatic processes. Samples from both sides of the Daly Gap show contrasting textures: basalts and basaltic andesites, found as lavas, are rich in macrocrysts, whereas dacites, only observed in crosscutting dykes, are very poor in macrocrysts. Moreover, modelling of the fractional crystallization process indicates a total fractionation of 43% to reach the most evolved basaltic andesites. The Daly Gap is thus interpreted as resulting from critical crystallinity that was reached in the basaltic andesites within the main storage region, precluding eruption of more evolved lavas. Some interstitial dacitic melt was extracted from the crystal mush and emplaced as dykes, possibly connected to small dacitic domes, now eroded away. In addition to the overall differentiation trend, the basalts to basaltic andesites display variable MgO, Cr and Ni contents at a given SiO2. Crystal accumulation and high pressure fractionation fail to predict this geochemical variability which is interpreted as resulting from variable extents of fractional crystallization. Geothermobarometry using recalculated primary magmas indicates last equilibration at about 1·3–1·5 GPa and at a temperature higher than the anhydrous peridotite solidus, pointing to a potential role of decompression melting. However, because the basalts are enriched in slab components and H2O compared to N-MORB, wet melting is highly likely.

scholarly journals Shallow-Mush reservoir conditions in the Fui Group small eruptive centres in the Southern Volcanic Zone (Chilean Andes)

2021 ◽  
Author(s):  
Francisca Mallea-Lillo ◽  
Miguel Ángel Parada ◽  
Eduardo Morgado ◽  
Darío Hübner ◽  
Claudio Contreras
Keyword(s):  
Volcanic Zone ◽  
Southern Volcanic Zone ◽  
Reservoir Conditions ◽  
Chilean Andes
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