Near-field modifications of stress induced by dyke injection at shallow depth

Bonafede, Maurizio; Danesi, Stefania

doi:10.1111/j.1365-246x.1997.tb05659.x

Cited by 55 publications

(42 citation statements)

References 20 publications

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“…However, fracturing as a consequence of dike emplacement is not a general rule (Bonafede and Danesi 1997) and the deformation pattern may be complicated by the presence of a layering with different mechanical properties (Gudmundsson and Brenner 2001;Gudmundsson et al 2002 and references therein).…”

Section: Etna and Its Summit And Flank Eruptions Over The Last 100 Yearsmentioning

confidence: 97%

What makes flank eruptions? The 2001 Etna eruption and its possible triggering mechanisms

Acocella

Neri

2003

Bulletin of Volcanology

180

108

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Most flank eruptions within a central stratovolcano are triggered by lateral draining of magma from its central conduit, and only few eruptions appear to be independent of the central conduit. In order to better highlight the dynamics of flank eruptions in a central stratovolcano, we review the eruptive history of Etna over the last 100 years. In particular, we take into consideration the Mount Etna eruption in 2001, which showed both summit activity and a flank eruption interpreted to be independent from the summit system. The eruption started with the emplacement of a~N-S trending peripheral dike, responsible for the extrusion of 75% of the total volume of the erupted products. The rest of the magma was extruded through the summit conduit system (SE crater), feeding two radial dikes. The distribution of the seismicity and structures related to the propagation of the peripheral dike and volumetric considerations on the erupted magmas exclude a shallow connection between the summit and the peripheral magmatic systems during the eruption. Even though the summit and the peripheral magmatic systems were independent at shallow depths (<3 km b.s.l.), petro-chemical data suggest that a common magma rising from depth fed the two systems. This deep connection resulted in the extrusion of residual magma from the summit system and of new magma from the peripheral system. Gravitational stresses predominate at the surface, controlling the emplacement of the dikes radiating from the summit; conversely, regional tectonics, possibly related to N-S trending structures, remains the most likely factor to have controlled at depth the rise of magma feeding the peripheral eruption.

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Section: Etna and Its Summit And Flank Eruptions Over The Last 100 Yearsmentioning

confidence: 97%

What makes flank eruptions? The 2001 Etna eruption and its possible triggering mechanisms

Acocella

Neri

2003

Bulletin of Volcanology

180

108

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“…Dykes induce stresses and displacements at and close to the Earth's surface when approaching it (Pollard and Holzhausen, 1979;Pollard et al, 1983;Rubin and Pollard, 1988;Bonafede and Olivieri, 1995;Rubin, 1995;Bonafede and Danesi, 1997;Acocella and Neri, 2003;Gudmundsson, 2003;Gudmundsson et al, 2008). Hence, surface deformation takes place before the eruption as well as at the moment the feeder intersects the Earth's surface.…”

Section: Feeder-dyke Propagationmentioning

confidence: 99%

Basaltic feeder dykes in rift zones: geometry, emplacement, and effusion rates

Galindo

Guðmundsson

2012

Nat. Hazards Earth Syst. Sci.

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Abstract. Most volcanic hazards depend on an injected dyke reaching the surface to form a feeder. Assessing the volcanic hazard in an area is thus related to understanding the condition for the formation of a feeder dyke in that area. For this latter, we need good field data on feeder dykes, their geometries, internal structures, and other characteristics that distinguish them from non-feeders. Unfortunately, feeder dykes are rarely observed, partly because they are commonly covered by their own products. For this reason, outcrops are scarce and usually restricted to cliffs, ravines, and man-made outcrops. Here we report the results of a study of feeder dykes in Tenerife (Canary Islands, Spain) and Iceland, focusing on their field characteristics and how their propagation is affected by existing structures. Although Holocene fissure eruptions have been common in both islands, only eleven basaltic feeder dykes have been identified: eight in Tenerife and three in Iceland. They are all well preserved and the relation with the eruptive fissure and/or the deposits is well exposed. While the eruptive fissures are generally longer in Iceland than in Tenerife, their feeders show many similarities, the main ones being that the feeder dykes (1) are generally sheet-shaped; (2) are segmented (as are the associated volcanic fissures); (3) normally contain elongated (prolate ellipsoidal) cavities in their central, topmost parts, that is, 2-3 m below the surface (with solidified magma drops on the cavity walls); (4) contain vesicles which increase in size and number close to the surface; (5) sometimes inject oblique dyke fingers into the planes of existing faults that cross the dyke paths; and (6) may reactivate, that is, trigger slip on existing faults. We analyse theoretically the feeder dyke of the 1991 Hekla eruption in Iceland. Our results indicate that during the initial peak in the effusion rate the opening (aperture) of the feeder dyke was as wide as 0.77 m, but quickly decreased to about 0.56 m. During the subsequent decline in the effusion rate to a minimum, the aperture decreased to about 0.19 m. At a later abrupt increase in the effusion rate, the feeder-dyke opening may have increased to about 0.34 m, and then decreased again as the effusion rate gradually declined during the end stages of the eruption. These thickness estimates fit well with those of many feeders in Iceland and Tenerife, and with the general dyke thickness within fossil central volcanoes in Iceland.

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“…According to Sipkin (1986), the non-double-couple mechanism might be due to tensile failure under high fluid pressure. Bonafede & Danesi (1997) obtained an analytical solution for the displacement and stress fields produced by a long vertical tensile fault in a uniform halfspace, using a Galerkin vector approach. Davis (1983) modelled the crustal deformation associated with hydrofracture by a dipping rectangular tensile fault beneath the surface of an elastic half-space.…”

Section: Introductionmentioning

confidence: 99%

Deformation of a uniform half-space due to a long inclined tensile fault

Singh¹,

Kumar²,

Rani

et al. 2002

Geophysical Journal International

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Summary The calculation of the deformation due to shear and tensile faults in a half‐space is a fundamental tool for the investigation of seismic and volcanic sources. The solution of the two‐dimensional problem of a long inclined shear fault is well‐known. The purpose of the present paper is to present closed‐form analytical expressions for the subsurface stresses and displacements caused by a long inclined tensile fault buried in a homogeneous isotropic half‐space. The expression for the Airy stress function satisfying appropriate boundary conditions at the surface of the half‐space is obtained. This Airy stress function is used to derive the expressions for the displacements and stresses at an arbitrary point of the half‐space. The variation of the displacement field with the horizontal distance from the fault is studied numerically. The effect of the depth of the upper edge of the fault and the dip angle on the deformation field is also examined.

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Near-field modifications of stress induced by dyke injection at shallow depth

Cited by 55 publications

References 20 publications

What makes flank eruptions? The 2001 Etna eruption and its possible triggering mechanisms

What makes flank eruptions? The 2001 Etna eruption and its possible triggering mechanisms

Basaltic feeder dykes in rift zones: geometry, emplacement, and effusion rates

Deformation of a uniform half-space due to a long inclined tensile fault

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