Fault growth & linkage Important to understand fault growth, interaction & linkage Continental extension and basin formation Controls on subsurface fluid flow Hydrocarbon exploration & production Minerals Groundwater Waste management/disposal Hazard assessment EARS5136 slide 1
3D Fault Array: Continuity EARS5136 slide 2
3D Fault Array: Reservoir models EARS5136 slide 3
EARS5136 slide 4
Displacement pattern on an isolated normal fault - after Barnett et al. (1987) Reverse drag r Displacement not to scale EARS5136 slide 5
Normal fault Coal field EARS5136 slide 6
Gulf Coast normal fault EARS5136 slide 7
Single fault North Sea seismic data a b EARS5136 slide 8
Fault surface topography EARS5136 slide 9
Normal fault - Oregon Throw and Separation Single fault from surface exposure in central Oregon Maximum separation (throw) near centre of fault. Gradual taper of separation profile from a maximum separation to zero at the fault tips. EARS5136 slide 10
West Africa: lower fault tips & conjugate faults EARS5136 slide 11
Low throw normal faults EARS5136 slide 12
Fault dimensions Aspect ratios average 2:1 but variable Linear throw gradients on isolated faults Non-linear on restricted faults Steeper gradients near overlapping tips EARS5136 slide 13
Fault aspect ratios Location Average aspect ratio Derbyshire coalmines UK 2.3 Timor Sea 2.2 Gulf Coast, USA 1.6 North Sea 2.4 From Nicol et al. (1996) EARS5136 slide 14
Fault dimensions From Nicol et al. (1996) EARS5136 slide 15
Restricted faults EARS5136 slide 16
Structure contours Beatrice field Map view Footwall anticline: Cross-section A-A shows form of footwall anticline. Maximum uplift near center of fault. Transverse section through hanging wall Hangingwall syncline: Maximum structural low near center of fault. Schlische, 1995 EARS5136 slide 17
Deformation around a fault Large scale faults generate isostatic footwall uplift and hangingwall subsidence Strain around the fault produces reverse drag Normal drag localized around the fault Flexural isostatic effects. EARS5136 slide 18
Isostasy EARS5136 slide 19
Flexural cantilever EARS5136 slide 20
Footwall uplift: Gullfaks field From: Husmo et al.(2002) EARS5136 slide 21
North Viking Graben From: Husmo et al.(2002) EARS5136 slide 22
Deformation around a fault Reverse drag profiles generate: footwall uplift hangingwall subsidence Relationship of structure contours to fault vary with slip direction Reverse drag does not imply a listric fault Earthquake related elastic strains relax to permanent bed deformation EARS5136 slide 23
Earthquake induced deformation < Imperial Valley earthquake 1940 Slip = e -3.5dist 0.03dist Strike-slip illustrates offsets Borah Peak earthquake 1983 > Lost River fault, Idaho EARS5136 slide 24
Deformation around a fault Radar interferometry image of ground deformation induced by Hector Mine earthquake Magnitude: 7.1 Depth 5±3 km Right-lateral strike-slip Length of surface rupture: 41 km Maximum surface offset 5.2 m EARS5136 slide 25
Fault drag profiles Empirical relationships for: Single event: Slip = e -3.5dist 0.03dist Multiple event steady state: Slip = e -5.5dist 0.004dist From Gibson et al. (1989) EARS5136 slide 26
Modelling bed contours Around blind faults (a-e) and synsedimentary fault (f). From Gibson et al. (1989) EARS5136 slide 27
Structure contours around an isolated normal fault EARS5136 slide 28
Hangingwall & footwall displacement Same in hangingwall and footwall for blind faults Greater hangingwall subsidence than footwall uplift for synsedimentary faults Percentage contribution of hangingwall displacement (HW) is given by: HW = 110 2θ/3 Where θ is fault dip and dip exceeds 30 degrees EARS5136 slide 29
Patterns around synsedimentary faults EARS5136 slide 30
Patterns around synsedimentary faults: a local example The Craven fault zone EARS5136 slide 31
Normal drag in footwall to a 6m throw normal fault: Carboniferous, Anglesey Normal drag profiles often highly localised around fault EARS5136 slide 32
Fault shape & linkage EARS5136 slide 33
Possible modes of fault linkage after Childs et al. (1995) a b c EARS5136 slide 34
a Displacement pattern correlated single fault 2D-seismic data set Middle East b EARS5136 slide 35
Displacement pattern correlated multiple faults 2D-seismic data set Middle East a b EARS5136 slide 36
Displacement patterns on overlapping faults from Childs et al. (1995) EARS5136 slide 37
Relay ramp structure and displacement patterns on overlapping faults from Huggins et al. (1995) A B Relay ramp structure and displacement patterns on overlapping faults. Summed throws give a coherent pattern. From Huggins et al. (1995) EARS5136 slide 38
Fault displacement and linkage patterns differences between higher and lower mapped horizons from Childs et al. (1995) EARS5136 slide 39
Segmented fault zone, Timor Sea from Childs et al. (1995) EARS5136 slide 40
Displacement patterns on overlapping faults from Childs et al. (1995) Fault 1 Fault 2 Aggregate throw EARS5136 slide 41
Relay zone structure from Peacock & Sanderson (1994) EARS5136 slide 42
Hard linked faults (Krantz 1988) Fault map Vertical separation EARS5136 slide 43
Relay ramps seismic mapping EARS5136 slide 44
Relay ramps seismic mapping EARS5136 slide 45
Relay ramp EARS5136 slide 46
Relay zone structure from Peacock & Sanderson (1994) EARS5136 slide 47
Fault displacement profiles From Nicol et al. (1996) EARS5136 slide 48
Geometric coherence From Walsh et al. (2003) EARS5136 slide 49
Different styles of transfer zones (Morley 1990) EARS5136 slide 50
NE-SW Cross-cutting faults NW-SE Interacting EARS5136 slide 51
Cross-cutting faults EARS5136 slide 52
Hard-linked splays EARS5136 slide 53
Conjugate faults EARS5136 slide 54
Conjugate faults EARS5136 slide 55
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Growth rates & slip rates Higher strain rate basins have higher slip rates on faults rather then more faults Large faults grow faster Large faults relatively large throughout growth of fault system Rates 0.004 to 1.0mmyr -1 : 0.188mmyr -1 (GOM) 0.030mmyr -1 (North Sea) 0.074mmyr -1 (Timor Sea) 0.248mmyr -1 (Aegean) 0.098mmyr -1 (Basin & Range) 0.049mmyr -1 (Kenya Rift) EARS5136 slide 57