Abstract
Long-term eruptive activity at the Santiaguito lava dome complex, Guatemala, is characterised by the regular occurrence of small-to-moderate size explosions from the active Caliente dome. Between November 2014 and December 2018, we deployed a seismo-acoustic network at the volcano, which recorded several changes in the style of eruption, including a period of elevated explosive activity in 2016. Here, we use a new catalogue of explosions to characterise changes in the eruptive regime during the study period. We identify four different phases of activity based on changes in the frequency and magnitude of explosions. At the two ends of the spectrum of repose times we find pairs of explosions with near-identical seismic and acoustic waveforms, recorded within 1–10 min of one another, and larger explosions with recurrence times on the order of days to weeks. The magnitude-frequency relationship for explosions at Santiaguito is well described by a power-law; we show that changes in b-value between eruptive regimes reflect temporal and spatial changes in rupture mechanisms, likely controlled by variable magma properties. We also demonstrate that the distribution of inter-explosion repose times between and within phases is well represented by a Poissonian process. The Poissonian distribution describing repose times changes between and within phases as the source dynamics evolve. We find that changes in source properties restrict the extrapolation of explosive behaviour to within a given eruptive phase, limiting the potential for long-term assessments of anticipated eruptive behaviour at Santiaguito.
Highlights
The Santiaguito lava dome complex, situated in the Western Highlands of Guatemala, has been continually active since 1922 (Harris et al, 2003)
Our observations agree with Harris et al (2003) that the behaviour of Santiaguito is commonly characterised by effusion of blocky lava flows from Caliente lava dome, punctuated by small-to-moderate sized explosions reaching up to 1.5 km above the vent (Global Volcanism Program, 2016b), as seen in phases 1, 3 and 4
The combination of visual and seismic observations at Santiaguito revealed four eruptive phases; this builds on previous studies by Lamb et al (2019) and Wallace et al (2020), as we present for the first time a description of phase 4
Summary
The Santiaguito lava dome complex, situated in the Western Highlands of Guatemala, has been continually active since 1922 (Harris et al, 2003). 620 m below the vent through the comparison of acoustic and seismic signal onsets (Sahetapy-Engel et al, 2008), between depths of 100 and 600 m though the analysis of rock samples taken from the lava flow units (Scott et al, 2012), and at about 300 m depth below the vent via Mogi source modelling of VLP signals (Johnson et al, 2014) These models proposed for the small-to-moderate gas-and-ash explosions do not apply to the large explosions during the period of heightened activity of 2016, which were sufficiently powerful to excavate the lava dome (Lamb et al, 2019). In this study we assess the seismic energy associated with individual explosions -a proxy for magnitude- and their variable occurrence rates; we exploit these measurements to investigate the magnitude-frequency relationship of explosions across different phases of eruptive behaviour with the aim of constraining four years of activity at Santiaguito
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
