Tectonic stresses on the boundary of the Aegean domain: “in situ” measurements by overcoring

Paquin, C.; Bloyet, J.; Angelidis, C.

doi:10.1016/0040-1951(84)90062-3

Cited by 17 publications

(6 citation statements)

References 5 publications

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“…Deformation in the crust in general occurs for very low values of the differential horizontal pressure (between I and 10 MPa). This is proven by in situ measurements [Paquin et al, 1984] and by mechanical analysis [Cloetingh and Wortel, 1985].…”

Section: Helens In Our Model Magmatic Pressure (Pma•) Up To 55mentioning

confidence: 76%

A Numerical Model for the Mechanical Behavior of Intraplate Volcanoes

Series

1989

Collected Reprint Series

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A new approach toward understanding the simulation using the finite element method. It will be mechanical behavior of intraplate volcanoes is offered by shown (see section below on the physical and elastic first postulating a geological model of the internal structure properties of the model) that the assumption of a linear and then developing an axisymmetric numerical simulation elastic and continuous medium is quite justified in this case. using the finite element method.This enables one to We are mainly interested in the distribution and intensity of consider the types of fracturing at various depths in terms stresses, since they give the most probable sites where of state of stress under specific conditions of loading. The fractures are going to open, keeping in mind that the geological model is based on comparative field studies of medium is continuous. The subject matter of this paper three volcanically active oceanic islands (Marion, Tristan da therefore belongs to the first category of problems discussed Cunha, and R•union) and a dormant one (Gough). The in the historical review below. model contains a shallow (3 km deep) magma chamber with Finally, in the discussion, the geological and numerical distinguishable floor, wall, and roof sections. A magma models are compared. column rises from the chamber toward a central cone at the surface. Depending on the structural level at which they Historical Development of Mechanical originate, different dyke and fracture patterns are generated. Modeling in VolcanologyFor the numerical simulation the medium is assumed to be linear elastic, continuous, and isotropic. Different loading Previous work on the mechanical behavior of volcanoes combinations are applied, including hydrostatic pressure plus uses both analytical and numerical methods, and can be magmatic pressure in the chamber and external pressure that subdivided into three categories. The first category of represents regional tectonic effects.It appears that the problems is the distribution of stresses inside a volcanic structural levels of the geological model can be adequately edifice. Mechanical models of the internal structure of explained by variations in the distribution, intensity, and volcanoes started with Anderson's [1935] studies on the trajectories of principal stresses o 1, 0 2, and .0 3. It is origin of the cone sheets and ring dykes of Ardnamurchan concluded that the shape of the magma source •s a major in Scotland. By an analytical approach, he derived the factor in the stress pattern. The effect of the driving equations of displacement components due to a radial point pressure (P -P x ) on the orientation of the principal dilatation and a vertical point-push acting in a weightless, stresses o 1 anco 2 is ats semi-infinite, elastic, isotropic half-space. He concluded o considered. The sloped surface of ma e the volcanic edifice is found to cause local rotation of the that cone sheets occupy tensile fractures while ring dykes stress field. Finally, the evolution of the stress field with occupy...

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Section: Helens In Our Model Magmatic Pressure (Pma•) Up To 55mentioning

confidence: 76%

A Numerical Model for the Mechanical Behavior of Intraplate Volcanoes

Series

1989

Collected Reprint Series

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“…Additionally, a number of in situ stress measurements in the area (PAQUIN et al, 1984), indicate the presence of a dominant E-W extensional stress regime. …”

Section: Papazachosmentioning

confidence: 99%

A spectral approach to moho depths estimation from gravity measurements in Epirus (NW Greece).

1988

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“…During the past two decades, the doorstopper technique has been used hequently and with great success for the mapping of regional tectonic stress fields in Europe (Greiner and Jllies, 1977; Kohlbeck et al, 1980; Martinetti and Ribacchi, 1980;Paquin et al, 1984). Compared with the doorstopper technique, the newly developed borehole slotter, originally designed at James Cook University, Townsville, Australia (Bock and Foruria, 19831, has s i g h c a n t advantages.…”

Section: Introductionmentioning

confidence: 99%

Strain measurements with the borehole slotter

Becker

Werner

1994

Terra Nova

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In the past, the doorstopper method has been used successfully for determining in situ tectonic stresses. Here an example is given about the application of the borehole slotter in the domain of tectonic stress determinations, which is an innovative strain relief technique without overcoring. Data are presented that test the reliability of the strain measurements by the borehole slotter under well‐known stress conditions, that indicate the reproducibility of borehole slotter strain data compared with those from doorstopper measurements, and that demonstrate the utility of the borehole slotter even for the determination of weak tectonic strains. In northern Switzerland the borehole slotter was used in a horizontal borehole under lithostatic loading conditions only, in a rock slope area with very heterogeneous stress conditions, and in a vertical borehole where tectonic stress should be dominant. The results show that the borehole slotter is a reliable technique, which allows precise determination of in situ strains. In addition, borehole slotter measurements are less time‐consuming and therefore less costly than most other stress‐measuring techniques—an important aspect in a future of reduced research budgets. Summary The borehole slotter is a strain relief technique, using a recoverable strain sensor that need not be glued to the rock surface and need not be overcored. It is quicker to use than most other stress or strain measuring techniques, especially in comparison to standard overcoring techniques (Fig. 14). The borehole slotter supplied convincing results with respect to principal stress orientations, in good agreement with: (i) principal stress orientations related to lithostatic stress conditions (Dittingen 2 site), (ii) palaeostress orientations during the main stage of Jura folding only 13 to 7 Ma (Laufen 1 site), (iii) the results of neighboring door‐stopper measurements (Dittingen 1 site). The borehole slotter tests do not supply stress magnitudes directly. Thus, the elastic properties of the rock mass have to be determined independently. Stress ratios from borehole dotter tests in Dittingen 2 are realistic. In conclusion, the borehole slotter is a fully developed probe to measure in situ strains in boreholes. It allows the reliable determination of a large number of data within a short time even in weakly stressed rocks. This makes the borehole slotter a powerful tool for the determination of contemporary regional tectonic stress fields.

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Tectonic stresses on the boundary of the Aegean domain: “in situ” measurements by overcoring

Cited by 17 publications

References 5 publications

A Numerical Model for the Mechanical Behavior of Intraplate Volcanoes

A Numerical Model for the Mechanical Behavior of Intraplate Volcanoes

A spectral approach to moho depths estimation from gravity measurements in Epirus (NW Greece).

Strain measurements with the borehole slotter

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