From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

Thomas S. Hudson; J. Michael Kendall; Matthew E. Pritchard; Jonathan D. Blundy; Joachim H. Gottsmann

doi:10.1016/j.epsl.2021.117268

From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

Thomas S. Hudson^*, J. Michael Kendall, Matthew E. Pritchard, Jonathan D. Blundy, Joachim H. Gottsmann

^*Corresponding author for this work

School of Earth Sciences

Research output: Contribution to journal › Article (Academic Journal) › peer-review

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Abstract

Uturuncu volcano is situated in the Bolivian Andes, directly above the world’s largest crustal body of silicic partial melt, the Altiplano-Puna Magma Body (APMB). Uturuncu last erupted 250,000 years ago, yet is seismically active and lies at the centre of a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using a newly developed velocity model, delineate the top and bottom of the APMB, reveal individual faults, and reconcile differences in depth distribution between previous studies. Spatial clustering analysis of these earthquakes reveals the orientations of the faults, which match stress orientations from seismic anisotropy. Earthquake b-values derived from moment magnitudes (1.44 ± 0.06) differ significantly from those using local magnitude measurements (0.80 ± 0.03). From these observations and theoretical justification, we suggest that, if possible, moment magnitudes should be used for accurate b-value analysis. We interpret b-values > 1 in terms of fluid-enhanced seismicity. Shallow seismicity local to Uturuncu yields b-values > 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults in a shallow hydrothermal system, likely driven by advection from the APMB. Intriguingly, events deeper than the APMB also yield large b-values (1.4), mapping the ascent into the lower crust of fluids that we infer as originating from a subducting slab. Cumulatively, these results provide a picture of an active magmatic system, where fluids are exchanged across the more ductile APMB, feeding a shallow, fault-controlled hydrothermal system. Such pathways of fluid ascent may influence our understanding of arc volcanism, control future volcanic eruptions and promote the accumulation of shallow hydrothermal ore deposits.

Original language	English
Article number	117268
Number of pages	13
Journal	Earth and Planetary Science Letters
Volume	577
Early online date	8 Nov 2021
DOIs	https://doi.org/10.1016/j.epsl.2021.117268
Publication status	Published - 1 Jan 2022

Bibliographical note

Funding Information:
We thank all the PLUTONS team for discussions relating to the interpretations that no doubt improved this manuscript. We especially thank Ying Liu for providing her seismic velocity model that was used to locate the seismicity in this study, as well as Patricia McQueen for providing additional datasets from previous studies for producing the literature comparison plots included in this study. We also thank T. Greenfield and three anonymous reviewers whose comments have certainly improved the manuscript. The seismic data analysed in this study is publicly available from IRIS. The earthquake detection algorithm used in this study, QuakeMigrate ( Winder et al., 2021 ), is available open source. We have also made the software used to calculate moment magnitudes and b-values, SeisSrcMoment ( Hudson, 2020 ), available open source. Some of the figures were produced using Generic Mapping Tools (GMT) ( Wessel et al., 2019 ). Much of the seismic data analysis was performed using ObsPy ( Beyreuther et al., 2010 ). This work, and TSH were funded by the NSFGEO-NERC grant NE/S008845/1 . MEP was funded by National Science Foundation grant EAR-1757495 . JDB thanks the Royal Society for financial support through a Research Professorship ( RP﹨R1﹨201048 ). The seismic data collection funded by the National Science Foundation grants 0908281 and 0909254, and the UK Natural Environment Research Council grant NE/G01843X/1 .

Publisher Copyright:
© 2021

Keywords

arc volcanism
earthquakes
magnitudes
seismology
tectonics
volcano

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@article{547d6ff864a24f588ac48f8649867a5f,

title = "From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia",

abstract = "Uturuncu volcano is situated in the Bolivian Andes, directly above the world{\textquoteright}s largest crustal body of silicic partial melt, the Altiplano-Puna Magma Body (APMB). Uturuncu last erupted 250,000 years ago, yet is seismically active and lies at the centre of a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using a newly developed velocity model, delineate the top and bottom of the APMB, reveal individual faults, and reconcile differences in depth distribution between previous studies. Spatial clustering analysis of these earthquakes reveals the orientations of the faults, which match stress orientations from seismic anisotropy. Earthquake b-values derived from moment magnitudes (1.44 ± 0.06) differ significantly from those using local magnitude measurements (0.80 ± 0.03). From these observations and theoretical justification, we suggest that, if possible, moment magnitudes should be used for accurate b-value analysis. We interpret b-values > 1 in terms of fluid-enhanced seismicity. Shallow seismicity local to Uturuncu yields b-values > 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults in a shallow hydrothermal system, likely driven by advection from the APMB. Intriguingly, events deeper than the APMB also yield large b-values (1.4), mapping the ascent into the lower crust of fluids that we infer as originating from a subducting slab. Cumulatively, these results provide a picture of an active magmatic system, where fluids are exchanged across the more ductile APMB, feeding a shallow, fault-controlled hydrothermal system. Such pathways of fluid ascent may influence our understanding of arc volcanism, control future volcanic eruptions and promote the accumulation of shallow hydrothermal ore deposits.",

keywords = "arc volcanism, earthquakes, magnitudes, seismology, tectonics, volcano",

author = "Hudson, \{Thomas S.\} and Kendall, \{J. Michael\} and Pritchard, \{Matthew E.\} and Blundy, \{Jonathan D.\} and Gottsmann, \{Joachim H.\}",

note = "Funding Information: We thank all the PLUTONS team for discussions relating to the interpretations that no doubt improved this manuscript. We especially thank Ying Liu for providing her seismic velocity model that was used to locate the seismicity in this study, as well as Patricia McQueen for providing additional datasets from previous studies for producing the literature comparison plots included in this study. We also thank T. Greenfield and three anonymous reviewers whose comments have certainly improved the manuscript. The seismic data analysed in this study is publicly available from IRIS. The earthquake detection algorithm used in this study, QuakeMigrate ( Winder et al., 2021 ), is available open source. We have also made the software used to calculate moment magnitudes and b-values, SeisSrcMoment ( Hudson, 2020 ), available open source. Some of the figures were produced using Generic Mapping Tools (GMT) ( Wessel et al., 2019 ). Much of the seismic data analysis was performed using ObsPy ( Beyreuther et al., 2010 ). This work, and TSH were funded by the NSFGEO-NERC grant NE/S008845/1 . MEP was funded by National Science Foundation grant EAR-1757495 . JDB thanks the Royal Society for financial support through a Research Professorship ( RP﹨R1﹨201048 ). The seismic data collection funded by the National Science Foundation grants 0908281 and 0909254, and the UK Natural Environment Research Council grant NE/G01843X/1 . Publisher Copyright: {\textcopyright} 2021",

year = "2022",

month = jan,

day = "1",

doi = "10.1016/j.epsl.2021.117268",

language = "English",

volume = "577",

journal = "Earth and Planetary Science Letters",

issn = "0012-821X",

publisher = "Elsevier B.V.",

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TY - JOUR

T1 - From slab to surface

T2 - Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

AU - Hudson, Thomas S.

AU - Kendall, J. Michael

AU - Pritchard, Matthew E.

AU - Blundy, Jonathan D.

AU - Gottsmann, Joachim H.

N1 - Funding Information: We thank all the PLUTONS team for discussions relating to the interpretations that no doubt improved this manuscript. We especially thank Ying Liu for providing her seismic velocity model that was used to locate the seismicity in this study, as well as Patricia McQueen for providing additional datasets from previous studies for producing the literature comparison plots included in this study. We also thank T. Greenfield and three anonymous reviewers whose comments have certainly improved the manuscript. The seismic data analysed in this study is publicly available from IRIS. The earthquake detection algorithm used in this study, QuakeMigrate ( Winder et al., 2021 ), is available open source. We have also made the software used to calculate moment magnitudes and b-values, SeisSrcMoment ( Hudson, 2020 ), available open source. Some of the figures were produced using Generic Mapping Tools (GMT) ( Wessel et al., 2019 ). Much of the seismic data analysis was performed using ObsPy ( Beyreuther et al., 2010 ). This work, and TSH were funded by the NSFGEO-NERC grant NE/S008845/1 . MEP was funded by National Science Foundation grant EAR-1757495 . JDB thanks the Royal Society for financial support through a Research Professorship ( RP﹨R1﹨201048 ). The seismic data collection funded by the National Science Foundation grants 0908281 and 0909254, and the UK Natural Environment Research Council grant NE/G01843X/1 . Publisher Copyright: © 2021

PY - 2022/1/1

Y1 - 2022/1/1

N2 - Uturuncu volcano is situated in the Bolivian Andes, directly above the world’s largest crustal body of silicic partial melt, the Altiplano-Puna Magma Body (APMB). Uturuncu last erupted 250,000 years ago, yet is seismically active and lies at the centre of a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using a newly developed velocity model, delineate the top and bottom of the APMB, reveal individual faults, and reconcile differences in depth distribution between previous studies. Spatial clustering analysis of these earthquakes reveals the orientations of the faults, which match stress orientations from seismic anisotropy. Earthquake b-values derived from moment magnitudes (1.44 ± 0.06) differ significantly from those using local magnitude measurements (0.80 ± 0.03). From these observations and theoretical justification, we suggest that, if possible, moment magnitudes should be used for accurate b-value analysis. We interpret b-values > 1 in terms of fluid-enhanced seismicity. Shallow seismicity local to Uturuncu yields b-values > 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults in a shallow hydrothermal system, likely driven by advection from the APMB. Intriguingly, events deeper than the APMB also yield large b-values (1.4), mapping the ascent into the lower crust of fluids that we infer as originating from a subducting slab. Cumulatively, these results provide a picture of an active magmatic system, where fluids are exchanged across the more ductile APMB, feeding a shallow, fault-controlled hydrothermal system. Such pathways of fluid ascent may influence our understanding of arc volcanism, control future volcanic eruptions and promote the accumulation of shallow hydrothermal ore deposits.

AB - Uturuncu volcano is situated in the Bolivian Andes, directly above the world’s largest crustal body of silicic partial melt, the Altiplano-Puna Magma Body (APMB). Uturuncu last erupted 250,000 years ago, yet is seismically active and lies at the centre of a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using a newly developed velocity model, delineate the top and bottom of the APMB, reveal individual faults, and reconcile differences in depth distribution between previous studies. Spatial clustering analysis of these earthquakes reveals the orientations of the faults, which match stress orientations from seismic anisotropy. Earthquake b-values derived from moment magnitudes (1.44 ± 0.06) differ significantly from those using local magnitude measurements (0.80 ± 0.03). From these observations and theoretical justification, we suggest that, if possible, moment magnitudes should be used for accurate b-value analysis. We interpret b-values > 1 in terms of fluid-enhanced seismicity. Shallow seismicity local to Uturuncu yields b-values > 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults in a shallow hydrothermal system, likely driven by advection from the APMB. Intriguingly, events deeper than the APMB also yield large b-values (1.4), mapping the ascent into the lower crust of fluids that we infer as originating from a subducting slab. Cumulatively, these results provide a picture of an active magmatic system, where fluids are exchanged across the more ductile APMB, feeding a shallow, fault-controlled hydrothermal system. Such pathways of fluid ascent may influence our understanding of arc volcanism, control future volcanic eruptions and promote the accumulation of shallow hydrothermal ore deposits.

KW - arc volcanism

KW - earthquakes

KW - magnitudes

KW - seismology

KW - tectonics

KW - volcano

UR - https://www.scopus.com/pages/publications/85118532405

U2 - 10.1016/j.epsl.2021.117268

DO - 10.1016/j.epsl.2021.117268

M3 - Article (Academic Journal)

AN - SCOPUS:85118532405

SN - 0012-821X

VL - 577

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

M1 - 117268

ER -

From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

Abstract

Bibliographical note

Keywords

Access to Document

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Transcrustal compressible fluid flow explains the Altiplano-Puna gravity and deformation anomalies

NSFGEO-NERC: Collaborative Research: Linking geophysics and volcanic gas measurements to constrain the transcrustal magmatic system at the Altiplano-Puna Deformation Anomaly

Investigating the relationship between pluton growth and volcanism at an active intrusions in the central Andes

Cite this

From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

Abstract

Bibliographical note

Keywords

Access to Document

Handle.net

Other files and links

Fingerprint

Research output

Transcrustal compressible fluid flow explains the Altiplano-Puna gravity and deformation anomalies

Projects

NSFGEO-NERC: Collaborative Research: Linking geophysics and volcanic gas measurements to constrain the transcrustal magmatic system at the Altiplano-Puna Deformation Anomaly

Investigating the relationship between pluton growth and volcanism at an active intrusions in the central Andes

Cite this