Journal of Structural Geology最新文献

{"title":"Estimating complete dyke dimensions from partial exposures","authors":"Sirshendu Kumar Biswas ,&nbsp;Tridib Kumar Mondal ,&nbsp;Avijit Saha ,&nbsp;Alaap Kumar Mukhopadhyay ,&nbsp;Archishman Mukherjee","doi":"10.1016/j.jsg.2025.105350","DOIUrl":"10.1016/j.jsg.2025.105350","url":null,"abstract":"<div><div>Knowledge of complete dyke dimensions is crucial to determine the actual aspect ratio which is indispensable in estimating their magma overpressure, depth of origin and even explosivity potential of fissure eruptions. A dearth of completely exposed dykes imposes considerable uncertainty on estimates of their aspect ratios. Therefore, we have pioneered a method of estimating complete dyke dimensions from their partial exposures lacking any tip. Considering dykes as dominantly opening mode fractures, the method is built upon the idealized canonical model of opening mode fractures and utilizes differential equation of ellipse, which is the predicted shape of fracture opening in the model, to estimate their full length, maximum width and aspect ratio from limited outcrop measurements. The validity of the method has been tested against ground data and published data. From its application to two partially exposed mafic dykes devoid of tips, one each from the Western and Eastern Dharwar Cratons of India we generated results from which we further calculate their magma overpressures and depths of origin. Although developed for dykes, the method has potential for wider application, since it can be used fundamentally to predict complete dimensions of any elliptical shaped natural features from their partial exposures.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"192 ","pages":"Article 105350"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The influence of columnar joints and joint pattern on near-surface normal faulting: An analog modeling approach","authors":"Lisa Winhausen ,&nbsp;Antonia Czepl ,&nbsp;Michael Kettermann ,&nbsp;Christoph von Hagke ,&nbsp;Janos L. Urai","doi":"10.1016/j.jsg.2025.105354","DOIUrl":"10.1016/j.jsg.2025.105354","url":null,"abstract":"<div><div>Normal faults at mid-ocean ridges develop massively dilatant structures close to the surface. Situated close to plate boundaries, these faults form in volcanic rocks such as basalt, which are characterized by columnar joints. These joints cause an orthotropic mechanical behavior of the rock mass, characterized by contrasting strong intact rock and weak, low-cohesion joint networks. To date, the influence of these columnar joints on the geometry and evolution of near-surface normal faults remains poorly understood. We present an analog modeling approach utilizing new analog modeling materials: i) layers of desiccated cornstarch forming drying cracks and resembling layered columnar joints in basaltic lava flows, and ii) systematically stacked blocks representing different joint patterns with varying block overlaps above vertical cooling joints. The geometric scaling of these models allows to assess the near-surface structures in the upper 50–150 m. The models reveal that fault formation is dominated by opening mode displacement reactivating the pre-existing joints and the style of deformation changes with progressive localization of the main fault. Observed structural features such as a tilted block bound between a main and antithetic fault, relay ramps, vertical mass transfer, and open cavities transfer well to the natural prototypes. Our newly developed experiments form a basis for future studies exploring fault processes in jointed rock masses.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"192 ","pages":"Article 105354"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An application of quartz grain analyses in earthquake-induced (palaeo)liquefaction studies","authors":"Szymon Świątek ,&nbsp;Karolina Lewińska ,&nbsp;Małgorzata Pisarska-Jamroży ,&nbsp;Christina Günter","doi":"10.1016/j.jsg.2025.105357","DOIUrl":"10.1016/j.jsg.2025.105357","url":null,"abstract":"<div><div>This study investigates the micromorphological changes in quartz grains as a result of seismically-induced liquefaction and their potential for distinguishing seismogenic soft-sediment deformation structures from other trigger mechanisms. The experimental analysis revealed distinct subtle and pronounced quartz cracks, edge corrosion, and advanced grain defragmentation. The findings suggest that these quartz alterations are strongly influenced by the degree of water mineralisation and the duration of exposure on it. Moreover, the study identified gold forms within quartz cracks, which developed after seismic activity and serve as a direct evidence of such activity. These microstructures provide new insights into the role of seismicity in the redistribution and deposition of minerals. Geochemical conditions, including pH and Eh, also played a critical role in the sediment's liquefaction behaviour. Our results highlight how chemical interactions, combined with seismic forces, contribute to quartz grains damage. These findings provide a novel approach for identifying seismically-induced deformation structures and assessing past seismic events in sedimentary records. The results also emphasize the significance of integrating quartz grain analysis in seismic risk assessments, improving the understanding of liquefaction mechanisms and potential hazards.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"193 ","pages":"Article 105357"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Displacement analysis of basin-scale reactivated normal faults: Insights from the West Netherlands Basin","authors":"Annelotte Weert ,&nbsp;Giovanni Camanni ,&nbsp;Marco Mercuri ,&nbsp;Kei Ogata ,&nbsp;Francesco Vinci ,&nbsp;Stefano Tavani","doi":"10.1016/j.jsg.2025.105356","DOIUrl":"10.1016/j.jsg.2025.105356","url":null,"abstract":"<div><div>Displacement-distance diagrams are valuable for studying fault interactions and growth. Examples of displacement patterns for faults that underwent multiple reactivation events are limited. This study presents along-strike and along-dip displacement-distance diagrams for nine basin-scale faults from the West Netherlands Basin, which has experienced multiple phases of displacement. The diagrams were derived from 3D seismic reflection data, covering 2300 km² and 6 km in depth. Due to the dataset size, we developed a semi-automated workflow to map faults, reduce noise, and generate displacement-distance diagrams. To determine the effects of both multiphase rifting and transpressive basin inversion on fault growth, we studied four faults only recording extensional events and five faults that also experienced inversion. We observed distinctive along-dip displacement patterns, characterized by piecewise curves, identifying pre-, syn-, and post-rift phases of fault growth, as well for a later inversion event. The shape of lateral displacement patterns suggests quasi-fixed lateral fault tips throughout the fault's history and faults developing their lateral lengths early, with later reactivation mainly increasing their vertical extent while accumulating displacement. In addition to improving our understanding of how faults grow through multiple reactivations, these results may provide insights into the growth-history of faults in other inverted rift basins world-wide.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"192 ","pages":"Article 105356"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143388063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrophysical Characterization of Metamorphic Rocks using X-ray Micro-CT data – Implications for fluid flow","authors":"Ritwik Chakraborty ,&nbsp;Michael Späth ,&nbsp;Akash Kumar ,&nbsp;Benjamin Busch ,&nbsp;Britta Nestler ,&nbsp;Manish A. Mamtani ,&nbsp;Christoph Hilgers","doi":"10.1016/j.jsg.2025.105338","DOIUrl":"10.1016/j.jsg.2025.105338","url":null,"abstract":"<div><div>The petrophysical properties (porosity and permeability) of rocks are significantly influenced by their microstructure and fabric anisotropy, which can be evaluated using X-ray micro-computed tomography (μCT). Through study of mica schists from the Singhbhum Shear Zone (Eastern India), we demonstrate the potential to perform X-ray micro-CT studies in metamorphic rocks and discuss the associated challenges in data processing. We show that automated thresholding of greyscale values from μCT data acquisition yields abnormally high porosity/permeability values in schists when compared to the values obtained from laboratory measurements of the same samples. We develop a <em>modus operandi</em> where the laboratory measured porosity value from an individual schist sample is used to calibrate the greyscale threshold range (designating void space) of μCT data from the same sample. This calibration is done using PACE3D numerical simulation framework that allows a multiphase-field approach, and it is shown that (a) porosities of schist derived from analysis of μCT data (post re-thresholding) fit well with laboratory measured values of respective samples and (b) anisotropy of permeability can be computed from μCT data. Permeability computed using the μCT data (post re-thresholding) vis-à-vis laboratory measurements are comparable in 4 out of 5 schist samples analysed here, when the samples are treated as a two phase system (void spaces as one phase and solid rock mass as the second phase) in PACE3D. The aberration in one schist sample is attributed to its heterogeneous layering and microstructure that comprises alternate layers of coarse and fine grain size aggregates of phyllosilicate + quartz. Re-computation of permeability by performing three-phase simulations for the above layered sample in PACE3D framework by introducing phyllosilicate as a third phase (in addition to void spaces and other mineral phases) yields results similar to the laboratory measurements. We conclude that our approach of integrating μCT data, laboratory measurement of petrophysical properties and microstructure modelling/simulation in PACE3D multiphase-field framework helps evaluate the role of rheological variations in controlling porosity/permeability. Thus this study has a bearing on enhancing knowledge about fluid flow in metamorphic rocks with possible implications for mineralization.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105338"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Co- and postseismic stress transfer on different types of faults in Southern Tibet by the 2015 Mw7.8 Gorkha earthquake","authors":"C. Yue ,&nbsp;C.Y. Qu ,&nbsp;X.F. Li ,&nbsp;L.Y. Meng ,&nbsp;X.H. Jiang ,&nbsp;D.L. Wu","doi":"10.1016/j.jsg.2024.105336","DOIUrl":"10.1016/j.jsg.2024.105336","url":null,"abstract":"<div><div>The influence of the 2015 Gorkha earthquake on the co- and postseismic Coulomb Failure Stress (CFS) of faults in Southern Tibet is a scientific issue that warrants further investigation. We employ the flat-ramp fault slip model to calculate the ΔCFS of nearly north-south-trending rifts and east-west-trending faults in Southern Tibet. This analysis considers the Mw7.8 main-shock, the Mw7.3 aftershock, afterslip, and viscoelastic relaxation, utilizing the Burgers rheological model. By integrating the postseismic deformation and b-value, we discuss the differences and similarities in ΔCFS and the underlying mechanisms.</div><div>The mainshock, aftershocks, and afterslip exhibit similar patterns of CFS effects, all acting as CFS triggers on the rifts. Viscoelastic relaxation has an unloading effect on the southern portion of the rifts, while it exerts a triggering effect on rifts located farther from the focal area, with the exception of the Dangreyongcuo rift. The influence of CFS on nearly east-west-trending faults is associated with their kinematic characteristics. Coseismic CFS triggering is concentrated in the near-source sections of the normal faults, with viscoelastic relaxation primarily resulting in unloading. The dextral strike-slip faults are governed by shear stress; the eastern sections serve as co- and postseismic CFS triggering areas, while the western sections are characterized as CFS shadow regions. Earthquakes along the Shenzha–Dingjie rift were primarily triggered by co- and postseismic CFS induced by the Gorkha earthquake. In contrast, earthquakes along the Xietongmen rift were mainly associated with elevated stress levels on the fault prior to the earthquake.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105336"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of backstop vertical position on the evolution of a backthrust dominated fold-and-thrust belt: Insights from viscous/brittle analogue models and comparison with cascadia","authors":"W.G. He ,&nbsp;F.O. Marques","doi":"10.1016/j.jsg.2024.105333","DOIUrl":"10.1016/j.jsg.2024.105333","url":null,"abstract":"<div><div>The most common features of a fold-and-thrust belt (FTB) are forward and backward thrusts, the distribution of which depends on several parameters that have been tested extensively. To further understand the development of FTBs in which an incompetent (viscous) detachment layer exists between an overlying deformed sedimentary pack (reverse faulting) and underlying undeformed basement, this study comprises four different viscous(bottom)/brittle(top) analogue models to test the effects of a new parameter, the vertical position of the piston's base relative to the viscous/brittle interface. Given that the models include a basal viscous layer, we also tested the effects of variable strain rate. The results indicate that both tested parameters significantly influence the internal structure of the sand wedge regarding wedge slope, structural style and thrust vergence. Finally, we compare the experimental results with the formation of the Cascadia FTB, and conclude that the model with shallow piston and constant piston velocity reproduces all the critical features of the composite structure of the Cascadia FTB, i.e. a foreland domain with dominant landward vergent thrusts and a shallow taper angle, a hinterland domain with dominant oceanward vergent thrusts and a flat topographic surface (taper angle = 0°), and a triangular zone separating the two domains with opposite vergences.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105333"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Consequences of preexisting faults on rifting patterns: Insights from multichannel seismic data of the Shunde rift, Northern South China Sea","authors":"Yancheng Xu,&nbsp;Jianye Ren","doi":"10.1016/j.jsg.2024.105331","DOIUrl":"10.1016/j.jsg.2024.105331","url":null,"abstract":"<div><div>Preexisting faults as the products of previous tectonic events are common in the passive continental margins. Recent studies have proposed the existence and significance of the preexisting faults in the Northern South China Sea (NSCS). Here, we present newly acquired 3D high-resolution seismic data across the Shunde Rift that allow us to observe a series of preexisting faults within the basement. The results suggest that the Shunde Rift is characterized by the presence of at least two sets of preexisting faults: a NE trending fault set and an E-W trending fault set. Considering the tectonic events that have occurred since the Mesozoic, we propose that the formation of E-W-trending faults can be attributed to the Late Triassic to Early Jurassic collision between Indochina and South China. Subsequently, NE trending faults developed due to northwestward subduction of the paleo-Pacific plate during Mid Jurassic to Late Cretaceous. Some of preexisting faults display reactivity during the early Cenozoic and exert primary control over the geometry and evolution processes of the Shunde Rift. The inherited faults primarily trend in a NE direction, significantly thinning the upper crust and forming a core complex type extension structure. This suggests that the NE trending preexisting faults may play a more important role in Cenozoic rifting of NSCS compared with E-W preexisting faults.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105331"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The low acoustic impedance of fault zones in the Wisting field, Barents Sea: Gas saturation or damage zone?","authors":"Jake H. Butcher ,&nbsp;Nestor Cardozo ,&nbsp;Lothar Schulte ,&nbsp;Luis Rojo","doi":"10.1016/j.jsg.2025.105347","DOIUrl":"10.1016/j.jsg.2025.105347","url":null,"abstract":"<div><div>The presence of faults in reservoirs can directly affect reservoir energy and feasibility in hydrocarbon bearing formations as well as repository potential for subsurface storage. Subsurface fault characterisation is an important but challenging workflow because a geoscientist is limited to the resolution of seismic data and sparse well data. The Barents Sea is renowned for exhumation generated gas seepage allowing preferential retainment of oil. In this study, observations in the fault zones of the Wisting field show reductions of acoustic impedance (A_imp) on seismic images. We characterise five intersecting E–W and N–S normal faults in the Wisting Central blocks using a novel approach, whereby low A_imp is mapped onto modelled fault surfaces and compared to parameters such as fault throw and shale gouge ratio. Low A_imp dominates E–W faults which exhibit more brittle response when compared to two N–S faults, where low A_imp values are sparse and the faults tip-out below a monocline. Two potential mechanisms causing the reduction of A_imp are proposed: 1) gas saturation, which can be as little as 2% to significantly reduce A_imp; 2) fault damage, which can decrease wave velocities and A_imp. The E–W faults in Wisting Central show higher reductions of A_imp than their N–S counterparts, indicating that they are either saturated with gas or have undergone higher damage.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105347"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain rates recorded in the perimeter-area relationship of recrystallized quartz aggregates from the Sandhill Corner shear zone, Maine, USA","authors":"Erik K. Anderson,&nbsp;Won Joon Song,&nbsp;Scott E. Johnson,&nbsp;Christopher C. Gerbi","doi":"10.1016/j.jsg.2024.105330","DOIUrl":"10.1016/j.jsg.2024.105330","url":null,"abstract":"<div><div>Current available methods for determining strain rates during viscous deformation are limited, generally relying on the preservation of appropriate microstructures. A lesser-known method to determine strain rates of monomineralic quartz aggregates relates the perimeter-area fractal dimension (D-value) of grain boundaries to deformation conditions. We explore this method by applying it to the Sandhill Corner shear zone (SCSZ), a seismogenic shear zone exhumed from the base of the frictional-to-viscous transition. Strain-rate patterns from D-values are similar to those from flow laws combined with grain size piezometry and predict comparable magnitudes to rates from flow laws using the theoretical piezometer of Shimizu (2012). We compare quartz D-values with proxies for grain shape and grain boundary roughness and find a clear correlation between D-value and grain size, suggesting it may record flow stress. We interpret the disparity in spatial trends between D-value and recrystallized grain size within the inner shear zone as reflecting the influence of transient deformation events associated with the seismic cycle. While the D-value is commonly referred to as a measure of the degree of serration or roughness of grain boundaries, this study suggests a more complex interrelationship of the D-value, grain size, aspect ratio, and roundness. Future field work and experimental calibrations are encouraged to test our findings and refine strain-rate estimates derived from D-values.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"191 ","pages":"Article 105330"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}