Scale dependency of segmentation along the strike of normal faults.

2020 ◽  
Author(s):  
Vincent Roche ◽  
Tom Manzocchi ◽  
Giovanni Camanni ◽  
Conrad Childs ◽  
Vasileios Papanikolaou
Keyword(s):  
Seismic Reflection ◽  
Normal Faults ◽  
Scale Dependency ◽  
3D Seismic ◽  
Critical Importance ◽  
Scale Invariant ◽  
Fault Segmentation ◽  
Similar Deformation

<p>The present study provides insights on the segmented nature of normal faults as a function of scale, and attempts to identify whether segmentation is scale invariant, scale dependent or hierarchical. This is a topic of critical importance for studies of fault development and in modelling exercises where one needs to extrapolate observations at one scale to other scales. </p><p>Results are based on data observed in the Blue Lias in Somerset (UK), in Fumanya mine (Spain) and in a 3D seismic reflection survey in the Bonaparte Basin (Australia). Fault segmentation is investigated quantitatively based on previously established methodologies and we focus on neutral relay zones observed between fault segments along the strike of the normal faults.</p><p>We found that there are quantitative indications that the shape of the relay zones, the breaching of the relays and the degree of segmentation are all scale independent in Kilve and Fumanya. We propose that this is related to the low variability across scales in the geological parameters controlling segmentation, due to the relative homogeneity of the rock medium across the studied scales, the lack of influence of pre-existing faults or fractures, and the similar deformation histories for all studied faults. By contrast, faults show scale dependency in the Bonaparte Basin where large faults are under the influence of an oblique reactivation of pre-existing faults. Independently of the area, segmentation observed continuously through scale stresses the need to take into account resolution of observation in discussing fault development.</p>

Three-dimensional geometries of relay zones in normal faults

2020 ◽  
Author(s):  
Giovanni Camanni ◽  
Vincent Roche ◽  
Conrad Childs ◽  
Tom Manzocchi ◽  
John Walsh ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Early Stage ◽  
Sedimentary Basins ◽  
Normal Faults ◽  
3D Seismic ◽  
Zone Structure ◽  
Cross Sectional ◽  
Mechanical Heterogeneity ◽  
Seismic Reflection Data ◽  
Fault Surface

<p>Individual normal faults are rarely single planar surfaces and often comprise arrays of fault segments arising from the earliest stages of fault propagation. Current models for the geometry and formation of relay zones between adjacent fault segments have been informed mainly by 2D analysis from either maps or cross-sections observed in outcrop and, to a lesser extent, by the analysis of relay zones from 3D seismic reflection data. Using high quality 3D seismic reflection datasets from a selection of sedimentary basins, we investigate fundamental characteristics of segmentation from the analysis of 67 normal faults with modest displacements (< ca. 190 m) which preserve the 3D geometry of 532 relay zones. Our analysis shows that relay zones most often develop by bifurcation from a single fault surface but can also arise from the formation of segments which are disconnected in 3D. Relay zones generally occur between fault segments that step in either the dip or strike direction, and oblique relay zones with an intermediate orientation are less frequent. This is attributed to the influence of mechanical stratigraphy, and to a tendency for faults to locally propagate laterally and vertically rather than obliquely. Cross-sectional stepping of relay zones typically forms contractional rather than extensional relay zones, a configuration which is attributed to the development of early stage Riedel shears associated with fault localisation. Comparing datasets from different geological settings suggests that the mechanical heterogeneity of the faulted sequence and the influence of pre-existing structure are the underlying controls on the geometrical characteristics of relay zones in normal faults, and different combinations of these two controls can account for the variation in fault zone structure observed between datasets.</p>

scholarly journals Evolution of a Normal Fault System, northern Graben, Taranaki Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Hamish Cameron
Keyword(s):  
New Zealand ◽  
Seismic Reflection ◽  
Normal Fault ◽  
Growth Patterns ◽  
Fault System ◽  
Normal Faults ◽  
3D Seismic ◽  
Fault Evolution ◽  
Migration Pathways ◽  
Insight Into

<p>This study investigates the evolution (from initiation to inactivity) of a normal fault system in proximity to active petroleum systems within the Taranaki Basin, New Zealand. The aim of this research is to understand the evolution, interaction, and in some cases, death of normal faults in a region undergoing progressive regional extension. This research provides insight into the geometry, development, and displacement history of new and reactivated normal fault evolution through interpretation of industry standard seismic reflection data at high spatial and temporal resolution. Insight into normal fault evolution provides information on subsidence rates and potential hydrocarbon migration pathways.  Twelve time horizons between 1.2 and 35 Ma have been mapped throughout 1670 square kilometres of the Parihaka and Toro 3D seismic reflection surveys. Fault displacement analysis and backstripping have been used to determine the main phases of fault activity, fault growth patterns, and maximum Displacement/Length ratios. The timing, geometry, and displacement patterns for 110 normal faults with displacements >20 m have been interpreted and analysed using Paradigm SeisEarth and TrapTester 6 seismic interpretation and fault analysis software platforms.  Normal faults within the Parihaka and Toro 3D seismic surveys began developing at ˜11 Ma, with the largest faults accruing up to 1500 m of displacement in <10 Myr (mean throw displacement rate of 0.15mm/yr). Approximately 50% of the 110 mapped faults are associated with pre-existing normal faults and have typical cumulative displacements of ˜20 – 1000 m, with strike parallel lengths of <1 – 23 km. In contrast, new faults have typically greater displacements of 20 – 1400 m, and are generally longer with, with strike parallel lengths of ˜1 – 33 km.   New faults were the first faults within the system to become inactive when strain rates decreased from 0.06 – 0.03 between 3.6 and 3.0 Ma. Eight of the largest faults with > 1000 m cumulative displacement reach the seafloor and are potentially active at present day. An earthquake on one of these faults could be expected to produce MW 2.2 based on the maximum strike-parallel length of the fault plane.</p>

scholarly journals A snapshot of the earliest stages of normal fault development

2021 ◽  
Author(s):  
Ahmed Alghuraybi ◽  
Rebecca Bell ◽  
Chris Jackson
Keyword(s):  
Seismic Reflection ◽  
Spatial Scales ◽  
Normal Fault ◽  
Normal Faults ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Temporal And Spatial ◽  
Fault Growth ◽  
Lateral Propagation

Despite decades of study, models for the growth of normal faults lack a temporal framework within which to understand how these structures accumulate displacement and lengthen through time. Here, we use borehole and high-quality 3D seismic reflection data from offshore Norway to quantify the lateral (0.2-1.8 mmyr-1) and vertical (0.004-0.02 mmyr-1) propagation rates (averaged over 12-44 Myr) for several long (up to 43 km), moderate displacement (up to 225 m) layer-bound faults that we argue provide a unique, essentially ‘fossilised’ snapshot of the earliest stage of fault growth. We show that lateral propagation rates are 90 times faster than displacement rates during the initial 25% of their lifespan suggesting that these faults lengthened much more rapidly than they accrued displacement. Although these faults have slow displacement rates compared with data compiled from 30 previous studies, they have comparable lateral propagation rates. This suggests that the unusual lateral propagation to displacement rate ratio is likely due to fault maturity, which highlights a need to document both displacement and lateral propagation rates to further our understanding of how faults evolve across various temporal and spatial scales.

scholarly journals Evolution of a Normal Fault System, northern Graben, Taranaki Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Hamish Cameron
Keyword(s):  
New Zealand ◽  
Seismic Reflection ◽  
Normal Fault ◽  
Growth Patterns ◽  
Fault System ◽  
Normal Faults ◽  
3D Seismic ◽  
Fault Evolution ◽  
Migration Pathways ◽  
Insight Into

<p>This study investigates the evolution (from initiation to inactivity) of a normal fault system in proximity to active petroleum systems within the Taranaki Basin, New Zealand. The aim of this research is to understand the evolution, interaction, and in some cases, death of normal faults in a region undergoing progressive regional extension. This research provides insight into the geometry, development, and displacement history of new and reactivated normal fault evolution through interpretation of industry standard seismic reflection data at high spatial and temporal resolution. Insight into normal fault evolution provides information on subsidence rates and potential hydrocarbon migration pathways.  Twelve time horizons between 1.2 and 35 Ma have been mapped throughout 1670 square kilometres of the Parihaka and Toro 3D seismic reflection surveys. Fault displacement analysis and backstripping have been used to determine the main phases of fault activity, fault growth patterns, and maximum Displacement/Length ratios. The timing, geometry, and displacement patterns for 110 normal faults with displacements >20 m have been interpreted and analysed using Paradigm SeisEarth and TrapTester 6 seismic interpretation and fault analysis software platforms.  Normal faults within the Parihaka and Toro 3D seismic surveys began developing at ˜11 Ma, with the largest faults accruing up to 1500 m of displacement in <10 Myr (mean throw displacement rate of 0.15mm/yr). Approximately 50% of the 110 mapped faults are associated with pre-existing normal faults and have typical cumulative displacements of ˜20 – 1000 m, with strike parallel lengths of <1 – 23 km. In contrast, new faults have typically greater displacements of 20 – 1400 m, and are generally longer with, with strike parallel lengths of ˜1 – 33 km.   New faults were the first faults within the system to become inactive when strain rates decreased from 0.06 – 0.03 between 3.6 and 3.0 Ma. Eight of the largest faults with > 1000 m cumulative displacement reach the seafloor and are potentially active at present day. An earthquake on one of these faults could be expected to produce MW 2.2 based on the maximum strike-parallel length of the fault plane.</p>

scholarly journals Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 117
Author(s):  
Maria Filomena Loreto ◽  
Camilla Palmiotto ◽  
Filippo Muccini ◽  
Valentina Ferrante ◽  
Nevio Zitellini
Keyword(s):  
Seismic Reflection ◽  
Magnetic Data ◽  
Normal Faults ◽  
Sedimentary Sequence ◽  
Initiation Zone ◽  
Arc Setting ◽  
Seismic Reflection Profiles ◽  
Back Arc ◽  
Flower Structures ◽  
Tyrrhenian Basin

The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.

Seismic Reflection Expression of Reactivated Structures in the New Madrid Rift Complex

1988 ◽  
Vol 59 (4) ◽  
pp. 141-150 ◽  
Author(s):  
John. L. Sexton
Keyword(s):  
Seismic Reflection ◽  
Structural Features ◽  
Normal Faults ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Reflection Method ◽  
Intraplate Earthquakes ◽  
Reflection Data ◽  
Seismic Reflection Method ◽  
New Madrid

Abstract An important aspect of seismogenesis concerns the role of preexisting faults and other structural features as preferred zones of weakness in determining the pattern of strain accumulation and seismicity. Reactivation of zones of weakness by present day stress fields may be the cause of many intraplate earthquakes. To understand the relation between reactivated structures and seismicity, it is necessary to identify structures which are properly oriented with respect to the present-day stress field so that reactivation can occur. The seismic reflection method is very useful for identifying and delineating structures, particularly in areas where the structures are buried as in the New Madrid seismic zone. Application of the seismic reflection method in widely separated locations within the New Madrid rift complex has resulted in successful detection and delineation of reactivated rift-related structures which are believed to be associated with earthquake activity. The purpose of this paper is to discuss results from seismic reflection profiling in the New Madrid rift complex. Reflection data from several surveys including USGS Vibroseis* surveys in the Reelfoot rift area reveal reactivated faults and other deep rift-related structures which appear to be associated with seismicity. High-resolution explosive and Mini-Sosie** reflection surveys on Reelfoot scarp and through the town of Cottonwood Grove, Tennessee, clearly show reverse faults in Paleozoic and younger rocks which have been reactivated to offset younger rocks. A Vibroseis survey in the Wabash Valley area of the New Madrid rift complex provides direct evidence for a few hundred feet of post-Pennsylvanian age reactivation of large-offset normal faults in Precambrian-age basement rocks. Several earthquake epicenters have been located in the vicinity of these structures. In the Rough Creek graben, Vibroseis reflection data provide clear evidence for reactivation of basement faults. The success of these reflection surveys shows that well-planned seismic reflection surveys must be included in any program seeking to determine the relationship between preexisting zones of weakness and seismicity of an area.

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