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Griffith WA, Di Toro G, Pennacchioni G, Pollard DD, Nielsen S. Static stress drop associated with brittle slip events on exhumed faults. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jb005879] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wibberley CAJ, Yielding G, Di Toro G. Recent advances in the understanding of fault zone internal structure: a review. ACTA ACUST UNITED AC 2008. [DOI: 10.1144/sp299.2] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractIt is increasingly apparent that faults are typically not discrete planes but zones of deformed rock with a complex internal structure and three-dimensional geometry. In the last decade this has led to renewed interest in the consequences of this complexity for modelling the impact of fault zones on fluid flow and mechanical behaviour of the Earth's crust. A number of processes operate during the development of fault zones, both internally and in the surrounding host rock, which may encourage or inhibit continuing fault zone growth. The complexity of the evolution of a faulted system requires changes in the rheological properties of both the fault zone and the surrounding host rock volume, both of which impact on how the fault zone evolves with increasing displacement. Models of the permeability structure of fault zones emphasize the presence of two types of fault rock components: fractured conduits parallel to the fault and granular core zone barriers to flow. New data presented in this paper on porosity–permeability relationships of fault rocks during laboratory deformation tests support recently advancing concepts which have extended these models to show that poro-mechanical approaches (e.g., critical state soil mechanics, fracture dilatancy) may be applied to predict the fluid flow behaviour of complex fault zones during the active life of the fault. Predicting the three-dimensional heterogeneity of fault zone internal structure is important in the hydrocarbon industry for evaluating the retention capacity of faults in exploration contexts and the hydraulic behaviour in production contexts. Across-fault reservoir juxtaposition or non-juxtaposition, a key property in predicting retention or across-fault leakage, is strongly controlled by the three-dimensional complexity of the fault zone. Although algorithms such as shale gouge ratio greatly help predict capillary threshold pressures, quantification of the statistical variation in fault zone composition will allow estimations of uncertainty in fault retention capacity and hence prospect reserve estimations. Permeability structure in the fault zone is an important issue because bulk fluid flow rates through or along a fault zone are dependent on permeability variations, anisotropy and tortuosity of flow paths. A possible way forward is to compare numerical flow models using statistical variations of permeability in a complex fault zone in a given sandstone/shale context with field-scale estimates of fault zone permeability. Fault zone internal structure is equally important in understanding the seismogenic behaviour of faults. Both geometric and compositional complexities can control the nucleation, propagation and arrest of earthquakes. The presence and complex distribution of different fault zone materials of contrasting velocity-weakening and velocity-strengthening properties is an important factor in controlling earthquake nucleation and whether a fault slips seismogenically or creeps steadily, as illustrated by recent studies of the San Andreas Fault. A synthesis of laboratory experiments presented in this paper shows that fault zone materials which become stronger with increasing slip rate, typically then get weaker as slip rate continues to increase to seismogenic slip rates. Thus the probability that a nucleating rupture can propagate sufficiently to generate a large earthquake depends upon its success in propagating fast enough through these materials in order to give them the required velocity kick. This propagation success is hence controlled by the relative and absolute size distributions of velocity-weakening and velocity-strengthening rocks within the fault zone. Statistical characterisation of the distribution of such contrasting properties within complex fault zones may allow for better predictive models of rupture propagation in the future and provide an additional approach to earthquake size forecasting and early warnings.
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Affiliation(s)
- Christopher A. J. Wibberley
- Géosciences Azur, CNRS UMR6526, Université de Nice – Sophia Antipolis, 250 rue A. Einstein, 06560 Valbonne, France
- Present address: TOTAL, CSTJF, Av. Larribau, 64018 Pau, France (e-mail: )
| | - Graham Yielding
- Badley Geoscience Ltd, North Beck House, North Beck Lane, Hundleby, Lincolnshire PE23 5NB, UK
| | - Giulio Di Toro
- Università di Padova, Dipartimento di Geoscienze, Via Giotto 1, 35137 Padova, Italy
- Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Roma, Italy
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Imanishi K, Ellsworth WL. Source scaling relationships of microearthquakes at Parkfield, CA, determined using the SAFOD Pilot Hole Seismic Array. EARTHQUAKES: RADIATED ENERGY AND THE PHYSICS OF FAULTING 2006. [DOI: 10.1029/170gm10] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Beeler NM, Hickman SH. Stress-induced, time-dependent fracture closure at hydrothermal conditions. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2002jb001782] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- N. M. Beeler
- U.S. Geological Survey; Menlo Park California USA
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Mai PM, Beroza GC. A spatial random field model to characterize complexity in earthquake slip. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2001jb000588] [Citation(s) in RCA: 313] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- P. Martin Mai
- Department of Geophysics; Stanford University; Stanford California USA
| | - Gregory C. Beroza
- Department of Geophysics; Stanford University; Stanford California USA
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Pelletier JD. Spring-block models of seismicity: Review and analysis of a structurally heterogeneous model coupled to a viscous asthenosphere. GEOCOMPLEXITY AND THE PHYSICS OF EARTHQUAKES 2000. [DOI: 10.1029/gm120p0027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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