TY - JOUR
T1 - Rapid localized flank inflation and implications for potential slope instability at Tungurahua volcano, Ecuador
AU - Hickey, James
AU - Lloyd, Ryan
AU - Biggs, Juliet
AU - Arnold, David
AU - Mothes, Patricia
AU - Muller, Cyril
PY - 2020/3/15
Y1 - 2020/3/15
N2 - High rates of volcano surface deformation can be indicative of a forthcoming eruption, but can also relate to slope instability and possible flank collapse. Tungurahua volcano, Ecuador, has been persistently active since 1999 and has previously experienced catastrophic flank failures. During the ongoing eruptive activity, significant surface deformation has been observed, with the highest rates contained within the amphitheatre-shaped scar from the 3000-year-old failure on the west flank. However, the cause of this asymmetric deformation and how it might relate to slope stability has not been assessed. Here, for the first time, we present a range of models to test physical processes that might produce asymmetric deformation, which are then applied to slope stability. Our models are informed by InSAR measurements of a deformation episode in November 2015, which show a maximum displacement of ∼3.5 cm over a period of ∼3 weeks, during which time the volcano also experienced multiple explosions and heightened seismicity. Asymmetric flank material properties, from the rebuilding of the cone, cannot explain the full magnitude and spatial footprint of the observed west flank deformation. The inflation is inferred to be primarily caused by shallow, short-term, pre-eruptive magma storage that preferentially exploits the 3 ka flank collapse surface. Shallow and rapid pressurization from this inclined deformation source can generate shear stress along the collapse surface, which increases with greater volumes of magma. This may contribute to slope instability during future unrest episodes and promote flank failure, with general application to other volcanoes worldwide displaying asymmetric deformation patterns.
AB - High rates of volcano surface deformation can be indicative of a forthcoming eruption, but can also relate to slope instability and possible flank collapse. Tungurahua volcano, Ecuador, has been persistently active since 1999 and has previously experienced catastrophic flank failures. During the ongoing eruptive activity, significant surface deformation has been observed, with the highest rates contained within the amphitheatre-shaped scar from the 3000-year-old failure on the west flank. However, the cause of this asymmetric deformation and how it might relate to slope stability has not been assessed. Here, for the first time, we present a range of models to test physical processes that might produce asymmetric deformation, which are then applied to slope stability. Our models are informed by InSAR measurements of a deformation episode in November 2015, which show a maximum displacement of ∼3.5 cm over a period of ∼3 weeks, during which time the volcano also experienced multiple explosions and heightened seismicity. Asymmetric flank material properties, from the rebuilding of the cone, cannot explain the full magnitude and spatial footprint of the observed west flank deformation. The inflation is inferred to be primarily caused by shallow, short-term, pre-eruptive magma storage that preferentially exploits the 3 ka flank collapse surface. Shallow and rapid pressurization from this inclined deformation source can generate shear stress along the collapse surface, which increases with greater volumes of magma. This may contribute to slope instability during future unrest episodes and promote flank failure, with general application to other volcanoes worldwide displaying asymmetric deformation patterns.
KW - deformation
KW - Finite Element Analysis
KW - InSAR
KW - slope stability
KW - Tungurahua volcano
UR - http://www.scopus.com/inward/record.url?scp=85078141945&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2020.116104
DO - 10.1016/j.epsl.2020.116104
M3 - Article (Academic Journal)
AN - SCOPUS:85078141945
VL - 534
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
M1 - 116104
ER -