Geometry, kinematics and fracture pattern of the Bangestan anticline, Zagros, SW Iran

2011 ◽  
Vol 148 (5-6) ◽  
pp. 964-979 ◽  
Author(s):  
STEFANO TAVANI ◽  
FABRIZIO STORTI ◽  
BAHMAN SOLEIMANY ◽  
MOHAMMAD FALLAH ◽  
JOSEP A. MUÑOZ ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Fractured Reservoirs ◽  
Fracture Pattern ◽  
Strike Slip ◽  
Deformation Pattern ◽  
Fold Axis ◽  
Lateral Strike Slip ◽  
Kinematic Evolution ◽  
Bangestan Anticline ◽  
Extensional Structures

AbstractThrust-related anticlines in the Zagros Simply Folded Belt provide excellent exposed analogue structures for fractured reservoirs located in the more external sectors of the belt. In these structures it is possible to study the fracture network attributes and understand their relationships to the folding process, thus gathering fundamental information for fracture modelling in reservoirs. In this work we analyse the mesoscopic deformation pattern of the NW–SE-trending Bangestan anticline (SW Zagros, Iran) and discuss its relationship to the kinematic evolution of the hosting structure. The deformation pattern mostly includes extensional structures and pressure solution cleavages striking parallel to the fold axial trend (i.e. longitudinal), transversal extensional structures, and N–S- and E–W-striking extensional structures (oriented oblique to the fold axis). With the aid of deep wells and a transversal reflection seismic profile, we constructed a balanced cross-section of the anticline and propose a kinematic evolution pathway constrained by the mesoscopic deformation pattern. Longitudinal and transversal deformation structures developed before and/or in the very early stages of fold growth. During this stage, the Bangestan anticline grew as a set of unconnected décollement anticlines involving the Cambrian to Pliocenic sedimentary cover. In a later stage, inherited basement faults were reactivated with a right-lateral strike-slip component and the previously developed anticlines propagated laterally up to their complete linkage and thrust breakthrough. This produced the right-lateral strike-slip reactivation of longitudinal joints and the development of N–S- and E–W-striking extensional structures, which were also frequently reworked as strike-slip faults.

scholarly journals Tectonic inversion of the Dnieper–Donetsk Basin. Part 2. Geodynamic situations and kinematic mechanism of riftogenic structure deformations

2020 ◽  
Keyword(s):  
Sedimentary Cover ◽  
Kinematic Model ◽  
Strike Slip ◽  
The Body ◽  
Donets Basin ◽  
Donetsk Basin ◽  
Kinematic Evolution ◽  
Tectonic Inversion ◽  
Reverse Thrust ◽  
Kinematic Mechanism

Formulation of the problem. In the second part of the article, the geodynamic mode and the kinematic mechanism of destruction of the Dnieper–Donetsk Basin by tectonic movements of the Late Hercynian and Alpine stages of tectogenesis were studied. New results of tectonophysical studies of the structural–kinematic evolution of the Earth's crust of Dnieper–Donetsk Basin at the collision stage are presented. The subject of research is a complex of deformation structures that complicate the sedimentary cover in the transitional zone of with Donetsk Foldbelt. Review of previous publications and studies. Using instrumental definitions of tectonite vergence, data of reconstruction of stress fields and quantitative modeling of deformations, a original kinematic model of tectonic inversion of the Dnieper–Donetsk Basin was developed. Methods. Structural–kinematic analysis of the structural drawings of collisional deformation and tectonics structures was used for regional geotectonic studies. Results. Tectonic inversion of the Dnieper-Donetsk Basin and Donbass began at the Late Hercynian epoch as a result of collisional movements of the compression orogen on the outskirts of the Paleotethis. Tangential compression of the southwestern direction led to the formation of gentle tectonic faults in the sedimentary cover of the Western Donets Graben, along which a lattice of thrust faults was formed. For a set of extrusion of sedimentary rocks in the reverse–thrust mode from the axial super-compressed zone, tectonic transport of geomas took place in the direction of the zones of "geodynamic shadow" on the southern side. Collisional deformations of horizons by the mechanism of longitudinal bending of the layers caused the formation of linear uplift-folding in the northern part of the Graben, and echelons of scaly thrust covers in the southern. At the Mesozoic and Cenozoic epochs, in the mode of interference of the reverse–thrust and horizontal-strike-slip fields, the Hercynian thrust lattice and the near-fault uplift folds underwent collisional deformation with the formation of coulisse–jointed folded zones and echeloned thrust covers. Based on the kinematic model of tectonic inversion of the Western Donets Graben, the geodynamics of the formation of the transition zone between the Dnieper–Donets Basin and the Donetsk Foldbelt is reconstructed. These data are the basis for adjusting the regional schemes of tectonic and oil and gas geological zoning. Scientific novelty and practical significance. The grouping of the compression axes in the western part of the Donbass caused the formation of a gorst-like geoblock-stamp, under the pressure of which the dislocated geomasses were thrusting onto the syneclisic cover of the southeastern segment of the depression. In the Western Donetsk Graben, the allochthonous stratum formed the body of the tectonic wedging geomas segment. Along the main strike–slip faults, which form the "tectonic rails" of the invasion, geodynamic zones of displacement of geomas were formed, composed of en-echelon articulated upthrust-folds. In its foreland, at the ends of the main strike–slip faults, an advanced scaly compression fan was formed, and in the hinterland, folded sutures were formed on the roots of the thrust covers. The main result of the research is a fundamentally new kinematic model of tectonic inversion of the Dnieper-Donetsk Basin. The model provides that the deformations of the riftogenic structure within the Graben were carried out according to the kinematic mechanism of the formation of a transverse orocline protruding under the pressure of the tectonic geoblock-stamp of the Donetsk Foldbelt.

Fracture pattern of the Lower Paleozoic sedimentary cover in the Lublin Basin of southeastern Poland derived from seismic attribute analysis and structural restoration

2018 ◽  
Vol 6 (3) ◽  
pp. SH73-SH89 ◽  
Author(s):  
Mateusz Kufrasa ◽  
Łukasz Słonka ◽  
Piotr Krzywiec ◽  
Krzysztof Dzwinel ◽  
Jarosław Zacharski
Keyword(s):  
Sedimentary Cover ◽  
Fracture Pattern ◽  
Strike Slip ◽  
Normal Faults ◽  
Late Devonian ◽  
Structural Restoration ◽  
Stress Regime ◽  
Lower Paleozoic ◽  
Attribute Analysis ◽  
Fracture Modeling

We have characterized Late Devonian fracture systems in the northeastern part of the Lublin Basin in Poland using two independent approaches: (1) seismic data conditioning and volumetric attribute analysis and (2) structural restoration, geomechanical modeling, and fracture modeling. The study area was subjected to reverse faulting in the basement and fault-related folding at the end of Devonian. These late Devonian structures were not overprinted by later deformation events. We have applied a set of structurally oriented filters and seismic attributes aimed at highlighting discontinuities to reduce the seismic noise and improved the fracture visibility on structural steering volume. The main faults cutting intra-Neoproterozoic and intra-Ordovician horizons are principal east–west-striking reverse faults and minor northwest–southeast-oriented normal faults. Based on analysis of the seismic-scale faults, we have carried out fracture modeling for strike-slip and compressional stress fields, with a northwest–southeast-oriented axis of maximum compression. We have correlated tentative strikes for tensile, shear, and closing-mode fractures for both stress regimes, with fault-likelihood attribute maps. The observed fracture system can have developed in the strike-slip stress regime, although cracks generated due to gas overpressure, or of pre-Devonian age, are not excluded. The final fracture model may be extrapolated into Silurian strata, but the results should be perceived as a general approximation of structural trends due to significant differences in mechanical properties of Silurian shales and underlying Ordovician carbonates. Improved model calibration could be achieved after inspection of scanner image logs. We believe that understanding the fracture distribution within the gas-bearing Silurian strata may contribute to effective planning and performing of hydraulic fracturing because part of these fracture planes may be reopened and provide new conduits for fluid flow.

Strong Ground-Motion Measurements during the 2003 Bam, Iran, Earthquake

2005 ◽  
Vol 21 (1_suppl) ◽  
pp. 165-179 ◽  
Author(s):  
Mehdi Zaré ◽  
Hossein Hamzehloo
Keyword(s):  
Ground Motion ◽  
Local Time ◽  
Strong Ground Motion ◽  
Strike Slip ◽  
Bam Earthquake ◽  
Lateral Strike Slip ◽  
Slip Mechanism ◽  
Motion Measurements ◽  
The City ◽  
Strong Ground

The Bam earthquake of 26 December 2003 ( Mw 6.5) occurred at 01:56:56 (GMT, 05:26:56 local time) near the city of Bam in the southeast of Iran. Two strong phases of energy are seen on the accelerograms. The first comprises a starting subevent with right-lateral strike-slip mechanism located south of Bam. The mechanism of the second subevent was a reverse mechanism.

Pre-folding fracturing in a foredeep environment: insights from the Carseolani Mountains (central Apennines, Italy)

2021 ◽  
pp. 1-17
Author(s):  
Marco Mercuri ◽  
Luca Smeraglia ◽  
Manuel Curzi ◽  
Stefano Tavani ◽  
Roberta Maffucci ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Fracture Pattern ◽  
Pressure Solution ◽  
Fold Axis ◽  
Field Observations ◽  
Central Apennines ◽  
Structural Position ◽  
Deformation Structures ◽  
Thrust Belts ◽  
Belt System

Abstract Bedding-perpendicular joints striking parallel (longitudinal) and perpendicular (transverse) to both the axis of the hosting anticline and the trend of the foredeep-belt system are widely recognized in fold-and-thrust belts. Their occurrence has been commonly attributed to folding-related processes, such as syn-folding outer-arc extension, although they can also be consistent with a pre-folding foredeep-related fracturing stage. Here we report the pre-folding fracture pattern affecting the Pietrasecca Anticline, in the central Apennines (Italy), resolved by a detailed field structural analysis. Field observations, scan-lines and interpretation of virtual outcrops were used to study the intensity, distribution and the orientations of fracture pattern along the anticline. The fracture pattern of the Pietrasecca Anticline consists of longitudinal and transverse joints, oriented approximately perpendicular to bedding, and of a pre-folding longitudinal pressure-solution cleavage set, which is oblique to bedding regardless of the bedding dip. Cross-cutting relationships show that joints predated the development of the pressure-solution cleavage. Furthermore, joint intensity does not relate to the structural position along the anticline. Taken together, these observations suggest that jointing occurred in a foredeep environment before the Pietrasecca Anticline growth. Our work further demonstrates that joints striking parallel and orthogonal to the main fold axis do not necessarily represent syn-folding deformation structures.

Aftershocks and surface faulting associated with the intraplate Guinea, West Africa, earthquake of 22 December 1983

1987 ◽  
Vol 77 (5) ◽  
pp. 1579-1601
Author(s):  
C. J. Langer ◽  
M. G. Bonilla ◽  
G. A. Bollinger
Keyword(s):  
West Africa ◽  
Focal Mechanism ◽  
Main Shock ◽  
Strike Slip ◽  
Fault System ◽  
Epicentral Area ◽  
Lateral Strike Slip ◽  
Focal Mechanism Solutions ◽  
Short Period ◽  
East West

Abstract This study reports on the results of geological and seismological field studies conducted following the rare occurrence of a moderate-sized West African earthquake (mb = 6.4) with associated ground breakage. The epicentral area of the northwestern Guinea earthquake of 22 December 1983 is a coastal margin, intraplate locale with a very low level of historical seismicity. The principal results include the observation that seismic faulting occurred on a preexisting fault system and that there is good agreement among the surface faulting, the spatial distribution of the aftershock hypocenters, and the composite focal mechanism solutions. We are not able, however, to shed any light on the reason(s) for the unexpected occurrence of this intraplate earthquake. Thus, the significance of this study is its contribution to the observational datum for such earthquakes and for the seismicity of West Africa. The main shock was associated with at least 9 km of surface fault-rupture. Trending east-southeast to east-west, measured fault displacements up to ∼13 cm were predominantly right-lateral strike slip and were accompanied by an additional component (5 to 7 cm) of vertical movement, southwest side down. The surface faulting occurred on a preexisting fault whose field characteristics suggest a low slip rate with very infrequent earthquakes. There were extensive rockfalls and minor liquefaction effects at distances less than 10 km from the surface faulting and main shock epicenter. Main shock focal mechanism solutions derived from teleseismic data by other workers show a strong component of normal faulting motion that was not observed in the ground ruptures. A 15-day period of aftershock monitoring, commencing 22 days after the main shock, was conducted. Eleven portable, analog short-period vertical seismographs were deployed in a network with an aperture of 25 km and an average station spacing of 7 km. Ninety-five aftershocks were located from the more than 200 recorded events with duration magnitudes of about 1.5 or greater. Analysis of a selected subset (91) of those events define a tabular aftershock volume (26 km long by 14 km wide by 4 km thick) trending east-southeast and dipping steeply (∼60°) to the south-southwest. Composite focal mechanisms for groups of events, distributed throughout the aftershock volume, exhibit right-lateral, strike-slip motion on subvertical planes that strike almost due east. Although the general agreement between the field geologic and seismologic results is good, our preferred interpretation is for three en-echelon faults striking almost due east-west.

scholarly journals Study on the relationship between multi-stage strike-slip mechanism and basin evolution in Fangzheng fault depression

2018 ◽  
Vol 22 (4) ◽  
pp. 335-339
Author(s):  
Jingfeng Wu ◽  
Qi'an Meng ◽  
Xiaofei Fu ◽  
Yuling Ma ◽  
Meifeng Sun ◽  
...  
Keyword(s):  
Seismic Data ◽  
Structural Characteristics ◽  
Stage Structure ◽  
Tectonic Stress ◽  
Strike Slip ◽  
The West ◽  
Lateral Strike Slip ◽  
Slip Mechanism ◽  
Pull Apart Basin ◽  
Multi Stage

Fangzheng fault depression is controlled by the northern of the Tan-Lu fault zone. It undergoes multi-stage strike-slip, extrusion modification, and erosion of the thermal uplift, forming a tectonic pattern of uplifts connected with sags. Through the regional dynamic analysis, the study of the activity law of the western Pacific plate has clarified the formation and transformation of the regional tectonic stress field. Under the background of the multi-stage of the strike-slip mechanism in the northern part of the Tan-lu fault, the Fangzheng fault depression has a characteristic of the “left-lateral strike-slip pull-apart basin, right-lateral strike-slip extrusion transformation.” According to the difference of the strike-slip, the Fangzheng fault depression has divided into two parts: the East fault depression and the West fault depression. The seismic data, seismic attribute analysis, and geological modeling techniques have applied to analyze the two fault depressions, the East fault depression has actively controlled by the strike-slip activity, and the structure is complex. The seismic data quality is poor; the structure of the West Fault Depression is the opposite and structural characteristics of asymmetrical difference strike-slip in the East and West fault depressions. Interpretation of seismic sections through a slippery background, the strike-slip attributes of the whole fault depression from south to north are segmented, and the strike-slip mechanism from east to west is different. Under the control of the multi-stage strike-slip mechanism, the Fangzheng fault depression is divided into six stages of strike-slip evolution, corresponding to the six different stages of the strike-slip control basin, the formation process of the asymmetric difference strike-slip fault basin is clarified, which provides a reference for the study of the strike-slip pull-apart basin with multi-stage structure.

The southern Mexico block: main boundaries and new estimation for its Quaternary motion

2008 ◽  
Vol 179 (2) ◽  
pp. 209-223 ◽  
Author(s):  
Louis Andreani ◽  
Xavier Le Pichon ◽  
Claude Rangin ◽  
Juventino Martínez-Reyes
Keyword(s):  
North American ◽  
Triple Junction ◽  
Strike Slip ◽  
North American Plate ◽  
Southern Mexico ◽  
Active Deformation ◽  
Lateral Strike Slip ◽  
Counterclockwise Rotation ◽  
The North ◽  
Slip Partitioning

Abstract Numerous studies, mainly based on structural and paleomagnetic data, consider southern Mexico as a crustal block (southern Mexico block, SMB) uncoupled from the North American plate with a southeast motion with respect to North America, accommodated by extension through the central Trans-Mexican volcanic belt (TMVB). On the other hand, the accommodation of this motion on the southeastward boundary, especially at the Cocos–Caribbean–North American triple junction, is still debated. The boundary between the SMB and the North American plate is constituted by three connected zones of deformation: (1) left-lateral transtension across the central TMVB, (2) left-lateral strike-slip faulting along the eastern TMVB and Veracruz area and (3) reverse and left-lateral strike-slip faulting in the Chiapas area. We show that these three active deformation zones accommodate a counterclockwise rotation of the SMB with respect to the North American plate. We specially discuss the Quaternary motion of the SMB with respect to the surrounding plates near the Cocos–Caribbean–North American triple junction. The model we propose predicts a Quaternary counterclockwise rotation of 0.45°/Ma with a pole located at 24.2°N and 91.8°W. Finally we discuss the geodynamic implications of this counterclockwise rotation. The southern Mexico block motion is generally assumed to be the result of slip partitioning at the trench. However the obliquity of the subduction is too small to explain slip partitioning. The motion could be facilitated by the high thermal gradient and gravitational collapse that affects central Mexico and/or by partial coupling with the eastward motion of the Caribbean plate.

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