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Stress development and possible fault reactivation in and around producing gas reservoirs
Published in Katsuhiko Sugawara, Yuzo Obara, Akira Sato, Rock Stress, 2020
For the modelled conditions (steeply dipping normal fault intersecting a reservoir with a certain amount of throw in an extensional tectonic stress regime), a surrounding rock stiffer than the reservoir rock apparently results in an initial state of stress which shortens the way to failure in comparison to the case that Esur = Eres. Failure can then be reached in an earlier stage of depletion, eventually leading to a larger amount of fault slip. Calculations indeed show a larger amount of both normal and reverse fault slip with increasing values of Esur (Figure 4b). For compressional tectonic stress fields (K0> 1) and fault dip angles smaller than 45° + f/2 (f being the fault friction angle), other conditions are expected to apply.
Tectonics
Published in Aurèle Parriaux, Geology, 2018
The geometric problem is now well determined within the static state. What about the movements theoretically possible for this rock wedge? As we envision whether it is necessary to consolidate it using an anchor, it is necessary to examine all possible movements. The only condition is that the block rests on at least one of its sides. Three types of slipping are theoretically possible: Case 1: Sliding along the edge with friction on the foliation and on the fault (friction on Plane 1 and Plane 2); the direction of movement in this case is unique and corresponds to edge D.Case 2: Sliding on the foliation only after detachment of the two sides of the fault (friction on Plane 1); different directions of movement are thus possible depending on the resultant of the forces because the edge plays no role.Case 3: Sliding on the fault only after detachment of the gneiss layers (friction on Plane 1); same remark as for Plane 1.
Tectonics
Published in Aurèle Parriaux, Geology, 2018
The geometric problem is now well determined within the static state. What about the movements theoretically possible for this rock wedge? As we envision whether it is necessary to consolidate it using an anchor, it is necessary to examine all possible movements. The only condition is that the block rests on at least one of its sides. Three types of slipping are theoretically possible: Case 1: Sliding along the edge with friction on the foliation and on the fault (friction on Plane 1 and Plane 2); the direction of movement in this case is unique and corresponds to edge D.Case 2: Sliding on the foliation only after detachment of the two sides of the fault (friction on Plane 1); different directions of movement are thus possible depending on the resultant of the forces because the edge plays no role.Case 3: Sliding on the fault only after detachment of the gneiss layers (friction on Plane 1); same remark as for Plane 1.
The New Zealand Community Fault Model – version 1.0: an improved geological foundation for seismic hazard modelling
Published in New Zealand Journal of Geology and Geophysics, 2023
Hannu Seebeck, Russ Van Dissen, Nicola Litchfield, Philip M. Barnes, Andrew Nicol, Robert Langridge, David J. A. Barrell, Pilar Villamor, Susan Ellis, Mark Rattenbury, Stephen Bannister, Matthew Gerstenberger, Francesca Ghisetti, Rupert Sutherland, Hamish Hirschberg, Jeff Fraser, Scott D. Nodder, Mark Stirling, Jade Humphrey, Kyle J. Bland, Andrew Howell, Joshu Mountjoy, Vicki Moon, Timothy Stahl, Francesca Spinardi, Dougal Townsend, Kate Clark, Ian Hamling, Simon Cox, Willem de Lange, Paul Wopereis, Mike Johnston, Regine Morgenstern, Genevieve Coffey, Jennifer D. Eccles, Timothy Little, Bill Fry, Jonathan Griffin, John Townend, Nick Mortimer, Samantha Alcaraz, Cécile Massiot, Julie V. Rowland, James Muirhead, Phaedra Upton, Julie Lee
Two down-dip depths are provided in the NZ CFM v1.0: the seismically determined limit of faulting (D90; Ellis et al. 2021) (Figure S4); and a maximum fault rupture depth (Dfc; Dfcomb of Ellis et al. 2021) (Figure 8). The seismically determined depth of faulting above which 90% of crustal earthquakes occur (D90) was developed using a 2001–2010 GeoNet earthquake catalogue (Reyners et al. 2011) relocated within a 3-D New Zealand-wide velocity model (Eberhart-Phillips et al. 2010) processed in 2013 (Ellis et al. 2021). Dfc is derived from a combination of D90 and thermal-fault friction models and includes an extra factor representing rupture propagation into the conditional stability zone (Ellis et al. 2021). Dfc represents a maximum depth limit for rupture where fault slip is expected to taper to zero, but does not provide information on the depth at which maximum fault slip may occur (e.g. Figure 8). Use of either Dfc or D90 in specific downstream applications will depend on the purpose(s) for which fault-depth estimates are required (e.g. Van Dissen et al. 2022) (see New Zealand National Seismic Hazard Model 2022 section for an example). In this sense, no single down-dip depth estimate may satisfy the requirements of all ensuing applications, therefore, careful consideration is required as to which – or perhaps neither – of the two down-dip depths provided in the NZ CFM v1.0 are most appropriate.
Sea temperature variation associated with the 2021 Haiti Mw 7.2 earthquake and possible mechanism
Published in Geomatics, Natural Hazards and Risk, 2022
Lu Zhang, Meng Jiang, Feng Jing
To better understand the thermal anomalous signals preceding the earthquake, the hypothesis of earth degassing (Qiang et al. 1997), underground water responses (Asteriadis and Livieratos 1989) and heat generated by fault friction (Wu et al. 2000) have been proposed. In addition, the models of Lithosphere-Atmosphere-Ionosphere coupling (LAIC) (Pulinets and Ouzounov 2011) and Lithosphere-Coversphere-Atmosphere coupling (LCAC) (Wu et al. 2012) have been developed to explain the interaction among different geospheres during the final stage of earthquake preparation. The ionizing radiation by radon gas was considered to be the main source for the release of heat and other physical/chemical processes in the atmosphere (Pulinets et al. 2006). Another explanation was proposed by Freund (2002, 2003), who believed that the charge is generated and propagates in rocks due to the activated positive holes (P-hole) and flow out of the rock to cause the unusual signals in case of the build-up tectonic stresses prior to an earthquake.
The Strongest Possible Earthquake Ground Motion
Published in Journal of Earthquake Engineering, 2022
Our conclusions are also predicated on the assumption that in-situ velocities at which the faults slip do not exceed 2 m/s. Factors fundamentally limiting this value may be fault friction or rheology of the material surrounding the fault. It is also conceivable that owing to irregular fault topography, kinetic energy is constantly expended on the destruction of the roughness on the rupture surface. It is not our intention to speculate about a particular cause but to simply point out that there is no observational evidence that the velocities may be greater.