Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kilauea volcano

Grímsvötn Volcano is the most active volcano in Iceland, and its last three eruptions were in 1998, 2004, and 2011. Here we analyze the displacement around Grímsvötn during these last three eruptive cycles using 10 GPS stations. The observed displacements in this region generally contain a linear component of tectonic and glacio‐isostatic origin, in agreement with the previously estimated values of plate motions and vertical rebound. Larger amplitude deformation observed close to Grímsvötn at the GFUM continuous GPS station clearly reflects a major volcanic contribution superimposed on a tectonic component. We estimate and subtract the tectonic trend at this station using regional observed displacement. The direction and pattern of the residual volcanic displacement (for coeruptive and intereruptive periods) are consistent for all three of these eruptive cycles. The posteruptive inflation is characterized by an exponential trend, followed by a linear trend. In this study, we explain this temporal behavior using a new analytic model that has two connected magma chambers surrounded by an elastic medium and fed by a constant basal magma inflow. During the early posteruptive phase, pressure readjustment occurs between the two reservoirs, with replenishment of the shallow chamber from the deep chamber. Afterward, due to the constant inflow of magma into the deep reservoir, the pressurization of the system produces linear uplift. A large deep reservoir favors magma storage rather than surface emission. Based on displacement measured at GFUM station, we estimate an upper limit for the radius of the deep reservoir of ∼10 km.

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“…After Delaney and McTigue [1994], the relations between the injected volume and the overpressure variation in the two reservoirs are…”

Section: 1002/2013jb010569mentioning

confidence: 99%

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

et al. 2014

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“…This is the "Mogi model" (Mogi 1958), which has been used to account for the surface deformation due to inflation and deflation of pressured magma chambers beneath many volcanoes (cf. McTigue 1987;Delaney and McTigue 1994).…”

Section: Stress Fields Of Caldera-forming Magma Chambersmentioning

confidence: 99%

“…Furthermore, some magma chambers may be surrounded by rock shells that have non-elastic, e.g., viscoelastic, behavior (Bonafede et al 1986;Dragoni and Magnanensi 1989), and uplift of the roof of a magma chamber during inflation depends on its (commonly unknown) shape, which makes Eq. (11) less applicable (e.g., Delaney and McTigue 1994).…”

Section: Caldera Collapse and Ash-flow Eruptionsmentioning

confidence: 99%

Formation and development of normal-fault calderas and the initiation of large explosive eruptions

Guðmundsson

1998

Bulletin of Volcanology

121

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The ring fractures that form most collapse calderas are steeply inward-dipping shear fractures, i.e., normal faults. At the surface of the volcano within which the caldera fault forms, the tensile and shear stresses that generate the normal-fault caldera must peak at a certain radial distance from the surface point above the center of the source magma chamber of the volcano. Numerical results indicate that normal-fault calderas may initiate as a result of doming of an area containing a shallow sill-like magma chamber, provided that the area of doming is much larger than the cross-sectional area of the chamber and that the internal excess pressure in the chamber is smaller than that responsible for doming. This model is supported by the observation that many caldera collapses are preceded by a long period of doming over an area much larger than that of the subsequently formed caldera. When the caldera fault does not slip, eruptions from calderas are normally small. Nearly all large explosive eruptions, however, are associated with slip on caldera faults. During dip slip on, and doming of, a normal-fault caldera, the vertical stress on part of the underlying chamber suddenly decreases. This may lead to explosive bubble growth in this part of the magma chamber, provided its magma is gas rich. This bubble growth can generate an excess fluid pressure that is sufficiently high to drive a large fraction of the magma out of the chamber during an explosive eruption.

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“…An important geodetic quantity is the volume of ground surface uplift, the integral of vertical displacement over the deformed volcanic edifice, DV edifice . Confusion exists regarding how to relate this uplift volume to the change in content of an underlying magma chamber, but the paper by Delaney and McTigue (1994) gives valuable guidance. The purpose of this comment is to point out the additional importance of magma compression, volatile exsolution, and gas compression in relating uplift volume to changes in the mass of magma within a reservoir.…”

Section: Introductionmentioning

confidence: 99%

Comment on " Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kīlauea volcano" by P. T. Delaney and D. F. McTigue

Johnson

Sigmundsson

Delaney

2000

Bulletin of Volcanology

102

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In volcanoes that store a significant quantity of magma within a subsurface summit reservoir, such as Kīlauea, bulk compression of stored magma is an important mode of deformation. Accumulation of magma is also accompanied by crustal deformation, usually manifested at the surface as uplift. These two modes of deformation -bulk compression of resident magma and deformation of the volcanic edifice -act in concert to accommodate the volume of newly added magma. During deflation, the processes reverse and reservoir magma undergoes bulk decompression, the chamber contracts, and the ground surface subsides. Because magma compression plays a role in creating subsurface volume to accommodate magma, magma budget estimates that are derived from surface uplift observations without consideration of magma compression will underestimate actual magma volume changes.

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Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kilauea volcano

Cited by 115 publications

References 16 publications

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

Formation and development of normal-fault calderas and the initiation of large explosive eruptions

Comment on " Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kīlauea volcano" by P. T. Delaney and D. F. McTigue

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