Time evolution of stress under an artificial lake and its implication for induced seismicity

Withers, Robert J.; Nyland, E.

doi:10.1139/e78-157

Cited by 18 publications

(3 citation statements)

References 11 publications

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“…Because larger magnitude induced earthquakes are generated on critically stressed, preexisting fault structures [ Simpson , ], it is important to understand the fault structures in areas that might be susceptible to induced earthquakes, preferably before human activities enhance the possibility of large earthquakes. Although computational observations show that reservoir‐induced earthquakes occur in varying tectonic environments and water levels [ Roeloffs , ], larger reservoir‐induced earthquakes may generally favor strike‐slip and normal faulting tectonic regimes [ Simpson , ; Bell and Nur , ; Withers and Nyland , ; Snow , ]; both types of faulting occur in fault releasing bends and fault step‐overs. Fault bends and step‐overs are common along strike‐slip fault systems, and these locations can be stress points for earthquake rupture nucleation or termination [ Aki , , ; Allen et al , ; Kruepfer , ].…”

Section: Discussionmentioning

confidence: 99%

Structure of the Koyna‐Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

et al. 2015

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The Koyna-Warna area of India is one of the best worldwide examples of reservoir-induced seismicity, with the distinction of having generated the largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, the fault structure and tectonic setting that has accommodated the induced seismicity is poorly known, in part because the seismic events occur beneath a thick sequence of basalt layers. On the basis of the alignment of earthquake epicenters over an~50 year period, lateral variations in focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, and magnetotelluric), geomorphic data, and correlation with similar structures elsewhere, we suggest that the Koyna-Warna area lies within a right step between northwest trending, right-lateral faults. The sub-basalt basement may form a local structural depression (pull-apart basin) caused by extension within the step-over zone between the right-lateral faults. Our postulated model accounts for the observed pattern of normal faulting in a region that is dominated by north-south directed compression. The right-lateral faults extend well beyond the immediate Koyna-Warna area, possibly suggesting a more extensive zone of seismic hazards for the central India area. Induced seismic events have been observed many places worldwide, but relatively large-magnitude induced events are less common because critically stressed, preexisting structures are a necessary component. We suggest that releasing bends and fault step-overs like those we postulate for the Koyna-Warna area may serve as an ideal tectonic environment for generating moderate-to large-magnitude induced (reservoir, injection, etc.) earthquakes.

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Section: Discussionmentioning

confidence: 99%

Structure of the Koyna‐Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

et al. 2015

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“…It is intuitively clear that the weight of the full reservoir on the hanging wall of a thrust fault or on the foot wall of a normal fault tends to stabilize such faults. Several previous model studies based on simplified formulations [Bell and Nur, 1978;Withers and Nyland, 1978] have concluded that normal and strike slip faults directly beneath the reservoir are the most greatly destabilized faults and that destabilization of thrust faults at an edge of the reservoir is possible. The results presented here confirm these con- 5O • 4o o• 3o ,• 2o >• o '"'"""lf""""l"l"'"'"'"l'n"'""l"'"'"'"l"'"'"'"l ""'""" clusions and extend them by showing that the time during the annual water level cycle at which a fault is most destabilized also depends on the location and orientation of the fault, as well as on the diffusivity and Skempton's coefficient of the rock beneath the reservoir.…”

confidence: 99%

Fault stability changes induced beneath a reservoir with cyclic variations in water level

Roeloffs¹

1988

J. Geophys. Res.

326

216

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The stress and pore pressure changes produced by a steady periodic variation of water level on the surface of a uniform porous elastic half‐space are evaluated using the fully coupled (Biot) equations of elastic deformation and pore fluid flow. Diverse choices of material properties all give a coupled stress field differing from the elastic stress field by at most 0.035 po, where po is the water pressure at the bottom of the reservoir. Peak coupled pore pressure change can lag peak water level in the depth range 0 < (ω/2c)1/2z < π, where ω is frequency of the cyclic change in water level, c is diffusivity, and z is depth. The maximum lag increases as B decreases, where B is the ratio of pore pressure increase to mean compressive stress increase under undrained conditions. Directly beneath the reservoir, for example, peak pore pressure in an annual cycle can lag peak water level by at most 10 days if B = 0.80, but can lag by up to 122 days if B = 0.11. When cyclic water level changes are superimposed on the steady state reservoir level, the time during the cycle at which a fault is most destabilized depends on whether the weight of the reservoir stabilizes or destabilizes the fault, which, in turn, depends on its orientation and location relative to the reservoir. B and c also influence the timing of the greatest destabilization. If B and c are low, maximum destabilization at low water level is possible for faults that are stabilized by the weight of the reservoir; this mechanism may have operated at Lake Mead. The analysis suggests that induced seismic events should be separated into groups having a common focal mechanism and occurring in similar locations relative to the reservoir before studying the time at which the events occur relative to the water level. The fully coupled solution is compared with an uncoupled solution, with a solution that is coupled but which assumes incompressible solid and fluid constituents (consolidation) and with a decoupled solution in which the difference between the pore pressure field and B times the elastic mean compressive stress obeys a homogeneous diffusion equation. The uncoupled and consolidation solutions respectively underestimate and overestimate pore pressure during short‐term reservoir level fluctuations as well as at times short compared to that required to achieve steady state. In contrast, the decoupled solution agrees closely with the fully coupled solution for the problem studied here.

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“…The rate at which pore pressure responds at depth to the impoundment of the reservoir is a function of the permeability of the rock. Theoretical studies [Bell and Nur, 1978;Withers and Nyland, 1978] have considered the subsurface change in pore pressure due to reservoir impoundment. It is important to know the in situ permeability at Monticello Reservoir to compare the theoretical fluid diffusion time with the time history of seismicity so as to provide an additional test of our working hypothesis.…”

Section: Permeability Measurementsmentioning

confidence: 99%

In situ study of the physical mechanisms controlling induced seismicity at Monticello Reservoir, South Carolina

Zoback¹,

Hickman²

1982

J. Geophys. Res.

127

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In two --•l.l-km-deep wells, the magnitudes of the principal in situ stresses, pore pressure, permeability, and the distribution of faults, fractures, and joints were measured directly in the hypocentral zones of earthquakes induced by impoundment of Monticello Reservoir, South Carolina. Analysis of these data suggests that the earthquakes were caused by an increase in subsurface pore pressure sufficiently large to trigger reverse-type fault motion on preexisting fault planes in a zone of relatively large shear stresses near the surface. The measurements indicated (1) near-critical stress differences for reverse-type fault motion at depths less than 200-300 m, (2) possibly increased pore pressure at depth relative to preimpoundment conditions, (3) the existence of fault planes in situ with orientations similar to those determined from composite focal plane mechanisms, and (4) in situ hydraulic diffusivities that agree well with the size of the seismically active area and time over which fluid flow would be expected to migrate into the zone of seismicity. Our physical model of the seismicity suggests that infrequent future earthquakes will occur at Monticello Reservoir as a result of eventual pore fluid diffusion into isolated zones of low permeability. Future seismic activity at Monticello Reservoir is expected to be limited in magnitude by the small dimensions of the seismogenic zones.

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Time evolution of stress under an artificial lake and its implication for induced seismicity

Cited by 18 publications

References 11 publications

Structure of the Koyna‐Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

Structure of the Koyna‐Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

Fault stability changes induced beneath a reservoir with cyclic variations in water level

In situ study of the physical mechanisms controlling induced seismicity at Monticello Reservoir, South Carolina

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