Stress drop variation of deep-focus earthquakes based on empirical Greens function

AbstractSometimes, a rather high stress drop characterizes earthquakes induced by underground fluid injections or productions. In addition, long-term fluid operations in the underground can influence a seismogenic reaction of the rock per unit volume of the fluid involved. The seismogenic index is a quantitative characteristic of such a reaction. We derive a relationship between the seismogenic index and stress drop. This relationship shows that the seismogenic index increases with the average stress drop of induced seismicity. Further, we formulate a simple and rather general phenomenological model of stress drop of induced earthquakes. This model shows that both a decrease of fault cohesion during the earthquake rupture process and an enhanced level of effective stresses could lead to high stress drop. Using these two formulations, we propose the following mechanism of increasing induced seismicity rates observed, e.g., by long-term gas production at Groningen. Pore pressure depletion can lead to a systematic increase of the average stress drop (and thus, of magnitudes) due to gradually destabilizing cohesive faults and due to a general increase of effective stresses. Consequently, elevated average stress drop increases seismogenic index. This can lead to seismic risk increasing with the operation time of an underground reservoir.

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Internal melt figures in ice by rapid adiabatic compression

Journal of Glaciology ◽

10.3189/s0022143000003890 ◽

1994 ◽

Vol 40 (134) ◽

pp. 132-134

Author(s):

R.E. Gagnon ◽

C. Tulk ◽

H. Kiefte

Keyword(s):

Phase Transformations ◽

Grain Boundaries ◽

Single Crystals ◽

Adiabatic Compression ◽

Air Bubbles ◽

Water Ice ◽

Deep Focus ◽

And Behavior ◽

First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

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A possible explanation for difference in stress drop between intraplate and interplate earthquakes

Geophysical Research Letters ◽

10.1029/2009gl040985 ◽

2009 ◽

Vol 36 (23) ◽

Cited By ~ 15

Author(s):

Naoyuki Kato

Keyword(s):

Stress Drop ◽

Interplate Earthquakes

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A Quasi-Greens Function Method for the Bending Problem of Simply Supported Polygonal Shallow Spherical Shells on Pasternak Foundation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.3215 ◽

2013 ◽

Vol 353-356 ◽

pp. 3215-3219

Author(s):

Shan Qing Li ◽

Hong Yuan

Keyword(s):

Function Method ◽

Homogeneous Boundary Condition ◽

Fredholm Integral Equations ◽

Pasternak Foundation ◽

Boundary Equation ◽

Spherical Shells ◽

Simply Supported ◽

Suitable Form ◽

Greens Function ◽

Good Agreement

The quasi-Greens function method (QGFM) is applied to solve the bending problem of simply supported polygonal shallow spherical shells on Pasternak foundation. A quasi-Greens function is established by using the fundamental solution and the boundary equation of the problem. And the function satisfies the homogeneous boundary condition of the problem. Then the differential equation of the problem is reduced to two simultaneous Fredholm integral equations of the second kind by the Greens formula. The singularity of the kernel of the integral equation is overcome by choosing a suitable form of the normalized boundary equation. The comparison with the ANSYS finite element solution shows a good agreement, and it demonstrates the feasibility and efficiency of the proposed method.

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Sharpening Deep Focus

Film Quarterly ◽

10.2307/1211918 ◽

1980 ◽

Vol 34 (2) ◽

pp. 62-64

Author(s):

Joe Heumann ◽

Charles H. Harpole

Keyword(s):

Deep Focus

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Damage of Short-Fiber-Reinforced Metal Matrix Composites Considering Cooling and Thermal Cycling

Journal of Engineering Materials and Technology ◽

10.1115/1.482788 ◽

1999 ◽

Vol 122 (2) ◽

pp. 203-208 ◽

Cited By ~ 20

Author(s):

Chuwei Zhou ◽

Wei Yang ◽

Daining Fang

Keyword(s):

Thermal Cycling ◽

Metal Matrix Composites ◽

Stress Drop ◽

Metal Matrix ◽

Failure Modes ◽

Short Fiber ◽

Uniaxial Tensile ◽

Matrix Composites ◽

Fiber Reinforced ◽

Matrix Damage

Mechanical properties and damage evolution of short-fiber-reinforced metal matrix composites (MMC) are studied under a micromechanics model accounting for the history of cooling and thermal cycling. A cohesive interface is formulated in conjunction with the Gurson-Tvergaard matrix damage model. Attention is focused on the residual stresses and damages by the thermal mismatch. Substantial stress drop in the uniaxial tensile response is found for a computational cell that experienced a cooling process. The stress drop is caused by debonding along the fiber ends. Subsequent thermal cycling lowers the debonding stress and the debonding strain. Micromechanics analysis reveals three failure modes. When the thermal histories are ignored, the cell fails by matrix damage outside the fiber ends. With the incorporation of cooling, the cell fails by fiber end debonding and the subsequent transverse matrix damage. When thermal cycling is also included, the cell fails by jagged debonding around the fiber tops followed by necking instability of matrix ligaments. [S0094-4289(00)01202-0]

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