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

Y Dzierma,H Wehrmann

doi:10.5194/nhess-10-2093-2010

Abstract

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.

Highlights

A series of volcanoes frequently erupting in historical times is situated in the Southern Volcanic Zone (SVZ) in Chile, an active volcanic arc produced by subduction of the Nazca Plate beneath the South American Plate
By means much beyond visual observation, it has been suggested in several recent studies that processes such as the transfer of stress and opening of fluid pathways following large earthquakes may play a fundamental role in triggering arc volcanism (e.g. Walter, 2007; Walter and Amelung, 2007; and references therein)
The statistical probability of future eruptions is determined for large volcanic centres in the SVZ, giving highest hazards for Llaima, Villarrica, and Nevados de Chillan

Summary

Introduction

A series of volcanoes frequently erupting in historical times is situated in the Southern Volcanic Zone (SVZ) in Chile, an active volcanic arc produced by subduction of the Nazca Plate beneath the South American Plate. By means much beyond visual observation, it has been suggested in several recent studies that processes such as the transfer of stress and opening of fluid pathways following large earthquakes may play a fundamental role in triggering arc volcanism (e.g. Walter, 2007; Walter and Amelung, 2007; and references therein). Those studies approached the seismic-volcanic interplay by numerical modelling. Advances looking at the temporal relationship have been provided by Watt et al (2009), demonstrating augmented eruptive activity following the 1960 Valdivia earthquake in Chile and the timescales at which the volcanic response may happen; this is addressed, by, e.g., Jupp et al (2004), Lemarchand and Grasso (2007)

Objectives

Methods

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Conclusion