Searching for patterns in caldera unrest. (27th July 2017)

• Record Type: Journal Article
• Authors: Sandri, Laura; Acocella, Valerio; Newhall, Chris
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 18:Number 7(2017)
• Page Start: 2748
• Page End: 2768
• Publication Date: 2017-07-27
• Subjects: caldera -- unrest -- eruption -- monitoring -- pattern recognition; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2017GC006870
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: The ultimate goal of volcanology is forecasting eruptions. This task is particularly challenging at calderas, where unrest is frequent, affects wider areas and its evidence is often masked by the activity of hydrothermal systems. A recent study has compiled a database on caldera unrest, derived from seismicity, geodetic, gravity, and geochemical monitoring data at calderas worldwide, from 1988 to 2014. Here we exploit this database, searching for the most recurring features of unrest and, in turn, its possible dynamics. In particular, we focus on (a) the duration of unrest at calderas; (b) recurring patterns in unrest; (c) unrest episodes culminating in eruptions, including time‐predictability or size‐predictability and a multivariate regression analysis. Our analysis indicates that preeruptive unrest is shorter than noneruptive unrest, particularly with open or semiplugged calderas, calderas with mafic or mixed composition of past eruptive products, or unrest driven by mafic magma; conversely, lack of data on preeruptive unrest driven by felsic magma and/or at felsic or plugged calderas prevents an analysis of these specific subsets. In addition, 72% of preeruptive unrest lasts <10 months and shows high seismicity and degassing. The remaining 28% (a) is essentially aseismic in calderas with open‐conduit (17%), or (b) lasts between 10 and 18 months, with seismicity and degassing, constituting a longer‐duration tail of the preeruptive unrest with seismicity and degassing (11%). Surface deformation is not always reliable to characterize preeruptive unrest. Our analysis suggests that magma may withstand only a limited period of "eruptability, " before becoming stored in the upper crust. Key Points: A data set of caldera unrest since 1988 is analyzed in search for recurring patterns; results are applied to an independent data set Preeruptive unrest is generally shorter than noneruptive one, mostly lasting less than 10 months and showing high seismicity and degassing Our analysis suggests that magma may withstand only a limited period of "eruptability, " before becoming stored in the upper crust