Journal of Structural Geology最新文献

{"title":"Distributions of throws, widths and scarp slopes on normal faults and their relations to fault growth: Insights from Auto_Throw code","authors":"Giampietro T ,&nbsp;Manighetti I ,&nbsp;Leclerc F ,&nbsp;Gaudemer Y","doi":"10.1016/j.jsg.2025.105393","DOIUrl":"10.1016/j.jsg.2025.105393","url":null,"abstract":"<div><div>Cumulative displacements on faults can tell us how they have accumulated over time, and thus how faults have grown. We approach this question from two angles, focusing on normal faults with topographic escarpment. First, we develop a code, Auto_Throw, to automate the measurements of throws on normal fault scarps. Using a piecewise linear fitting approach and basic slope and length constraints, Auto_Throw mathematically explores all possible configurations of scarps and offset surfaces on a topographic profile, so that a throw and its uncertainty are defined from the statistical analysis of tens to hundreds of measurements. Auto_Throw also measures the scarp slopes and the across-fault widths. We test Auto_Throw performance on 35 normal faults of different lengths and contexts, performing a million measurements. Second, we address the tectonic implications of the measurements. We conduct a global analysis of all fault data in order to smooth out site-dependent complexities and identify common features that may result from the fault growth process. We find that throws, scarp slopes and fault widths significantly vary along faults, yet in a similar manner for each fault quantity. Throw distributions show a common envelope shape, asymmetric with a long slip taper. Steepest scarp slopes are sub-constant along faults but systematically drop down towards fault tips. Fault width scales with throw, but a rough zone of constant width is identified off the faults. Tapering slip on a fault, shallowing of its scarp slope, and distributed deformation off its trace, could all be indicative of the fault lateral propagation.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"196 ","pages":"Article 105393"},"PeriodicalIF":2.6,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143636527","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":"Controls on shear band orientation in deforming porous rocks: Insights from improved microcrack segmentation method","authors":"Claudia Elijas-Parra ,&nbsp;Alexis Cartwright-Taylor ,&nbsp;Ian G. Main ,&nbsp;Rebeca E. Ursu ,&nbsp;Ian B. Butler ,&nbsp;Florian Fusseis","doi":"10.1016/j.jsg.2025.105404","DOIUrl":"10.1016/j.jsg.2025.105404","url":null,"abstract":"<div><div>High resolution, time-resolved X-ray imaging of deformation processes has revealed unprecedented detail on the microstructural and mechanical processes involved in system-scale failure during laboratory experiments. This has highlighted the role of the evolving crack population in controlling localisation. However, in porous rocks, accurate segmentation of evolving crack populations from the rock matrix and pre-existing pores is challenging because of the narrow aperture of cracks. Here we develop and test a new global statistical method of distinguishing between these three phases in tomographic slices, obtained from an X-ray transparent triaxial compression experiment on Clashach sandstone at 20 MPa effective pressure. Compared with a watershed-based method, the new method is less sensitive to artefacts of sampling at the voxel scale (<em>l</em> ≥ 40 μm). Furthermore, the segmented crack length distributions have a greater dynamic range, yielding exponents (1 ≤ <em>a</em>≤3) above 150 μm that are in the same range as those observed in field outcrop, while anisotropy in the crack orientation distribution is better represented. Using this new method, we observe the spontaneous localisation of cracks into a shear band, whose orientations evolve from a random distribution to one more favourably oriented for synthetic shear and tensile fracturing. The observed shear band orientation (∼60° dip) is intermediate between a directed percolation model (50°) and the mode of the crack orientation distribution in the shear band (66°).</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"196 ","pages":"Article 105404"},"PeriodicalIF":2.6,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684963","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 partitioning and fault interaction during the 2023 Mw 6.8 Al-Haouz earthquake, Western High Atlas, Morocco","authors":"F. Carboni ,&nbsp;M. Occhipinti ,&nbsp;R. Lanari ,&nbsp;F. Medina ,&nbsp;T.-E. Cherkaoui ,&nbsp;R. Gaspari ,&nbsp;C. Faccenna ,&nbsp;C. Chiarabba ,&nbsp;M. Porreca","doi":"10.1016/j.jsg.2025.105394","DOIUrl":"10.1016/j.jsg.2025.105394","url":null,"abstract":"<div><div>This study employs a multidisciplinary approach to identify the seismogenic fault responsible for the Mw 6.8 Al Haouz earthquake of September 8, 2023, in the Western High Atlas, Morocco. In addition, considering the oblique slip dynamics and strain partitioning characteristic of the region, the study investigates potential interactions between fault systems at depth. Our new relocation of the mainshock confirms the depth of the mainshock at ca. 28 km, while our relocated aftershocks reveal clusters concentrated near the Tizi n’Test fault (TnTf) and aligned patterns consistent with fault-controlled seismicity. Focal mechanisms of the mainshock indicate a compressive event involving two nodal planes: a high-angle NW-dipping plane and a low-angle SW-dipping plane. DInSAR analysis generated displacement maps for vertical and horizontal (E-W) components, revealing an asymmetric SW-verging uplift bounded, in the south, by the NW-dipping Tizi n’Test fault (TnTf). The Triangular Elastic Dislocation (TDE) method is conducted to simulate complex faults geometries using geological data and focal mechanism solution.</div><div>The NW-dipping TnTf shows a better fit with the observed deformation compared to the SW-dipping Jebilet Thrust (JTt), which contributed with a minor role. Coulomb stress changes calculated from the TDE model correlates with aftershocks distribution, further supporting the TnTf as the causative fault, with a partial influence of the JTt.</div><div>Our findings emphasize the value of integrating geodetic observations with advanced modelling to enhance the understanding of the seismotectonic framework, offering a refined reconstruction of the Western High Atlas's deformation processes during the 2023 Al Haouz earthquake.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"195 ","pages":"Article 105394"},"PeriodicalIF":2.6,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143594207","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":"Structural evolution of the southern Swayze greenstone belt, Superior Craton: Implications for the Neoarchean crustal dynamics","authors":"Qǐháng Wú ,&nbsp;Shoufa Lin ,&nbsp;Thomas Gemmell ,&nbsp;Sandra L. Kamo ,&nbsp;Jian Zhang ,&nbsp;Lijun Wang","doi":"10.1016/j.jsg.2025.105373","DOIUrl":"10.1016/j.jsg.2025.105373","url":null,"abstract":"<div><div>Numerous studies suggest that the Neoarchean may have been a transitional period from vertical tectonism to horizontal tectonism in crustal dynamics. The former is characterized by spontaneous gravitational redistribution of crustal materials, while the latter is characterized by partitioning of far-field tectonic stress into localized high shear zones and regional-scale strike-slip motion. However, how these combined crustal dynamics are manifested in the geological record remains poorly understood. In this study, a deformation analysis was carried out in the southern part of the Neoarchean Swayze greenstone belt, southeastern Superior Craton, as well as in the enclosing Ridout deformation zone. Our structural analysis reveals four generations (G₁ <!--> <!-->–<!--> <!-->G₄) of ductile deformation. G₁ deformation is preserved only in the pre-tectonic granitoid intrusion. G₂ deformation established the dome-and-keel architecture of the Swayze greenstone belt and is associated with regional F₂ folding, the S₂ foliation subparallel to the granitoid–greenstone boundary and the L₂ stretching lineation which exhibits a reversal in the plunge direction on the opposing granitoid–greenstone boundaries. The G₂ deformation zones show a granitoid-up/greenstone-down sense of shear. G₃ deformation is associated with oblique sinistral movement on the Ridout deformation zone possibly due to regional sinistral transpression. G₄ deformation is a reactivation event of pre-existing weak planes in the form of transcurrent dextral shearing. The kinematics of G₂ structures is interpreted to be the result of combined sagduction/diapirism and regional dextral shearing, thus implying a crustal condition that is “weak” enough to allow spontaneous crustal-scale gravitational readjustments while at the same time “strong” enough to transfer regional tectonic stress. In this sense, both styles of tectonism may have operated simultaneously in the Swayze greenstone belt. Our results support the hypothesis that the Neoarchean era is a transitional period during which the crustal dynamics evolved from being mainly vertical to horizontal and that the Swayze greenstone belt preserves evidence for the co-operation of both processes. Furthermore, our analysis, including temporal constraints, recognizes a comparable structural history between the Ridout deformation zone in the Swayze greenstone belt and the Cadillac-Larder Lake deformation zone in the Abitibi greenstone belt. However, discrepancies exist in terms of the vertical kinematics and the position of the deformation zone with respect to the syntectonic Timiskaming-type sedimentary assemblage. Therefore, we propose that the two deformation zones may have been initiated as separate entities rather than a coherent crustal-scale deformation corridor.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"195 ","pages":"Article 105373"},"PeriodicalIF":2.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579914","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":"Spatial arrangements and clustering of opening-mode fractures in experimental models of layered rocks","authors":"Myroslava Kravchuk ,&nbsp;Alexandre I. Chemenda ,&nbsp;Julien Ambre","doi":"10.1016/j.jsg.2025.105392","DOIUrl":"10.1016/j.jsg.2025.105392","url":null,"abstract":"<div><div>Arrays of opening-mode fractures were obtained in three-layer experimental models. They consist of a stiff, brittle competent Granular Rock Analog Material (GRAM) layer sandwiched between two more compliant incompetent elastomer layers. All layers are homogeneous with uniform properties and initially under hydrostatic stresses. Fracturing occurs during horizontal unloading (extension) under constant vertical compressive stress <span><math><mrow><msub><mi>σ</mi><mi>v</mi></msub></mrow></math></span>. The process begins with fractures having spacing (<span><math><mrow><mi>S</mi></mrow></math></span>) to layer thickness (<span><math><mrow><mi>T</mi></mrow></math></span>) ratio of <span><math><mrow><mi>Ω</mi><mo>=</mo><mi>S</mi><mo>/</mo><mi>T</mi><mo>≥</mo><mn>1</mn></mrow></math></span>. At nominal extension strain <span><math><mrow><msub><mi>ε</mi><mrow><mi>x</mi><mi>x</mi></mrow></msub><mo>&gt;</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span>, new fractures form closely to some of the initial ones. They initiate at the layer top and bottom and propagate both vertically and laterally, forming a linear fracture cluster (or corridor) in plan view. The <span><math><mrow><mi>Ω</mi></mrow></math></span> value within the cluster is 0.01–0.05, consistent with the natural prototypes. Then, other initial or newly formed fractures become centers of cluster growth until the entire layer is filled with clusters at <span><math><mrow><msub><mi>ε</mi><mrow><mi>x</mi><mi>x</mi></mrow></msub><mo>&gt;</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup></mrow></math></span>, marking the transition from strongly clustered to a more uniform distribution of now closely spaced fractures. All these spatial fracture arrangements also exist in nature, and according to our results depend on <span><math><mrow><msub><mi>ε</mi><mrow><mi>x</mi><mi>x</mi></mrow></msub></mrow></math></span>, controlled by the process driving the fracturing of competent layers. This process involves the lateral spreading of the incompetent materials under the vertical (lithostatic) compression <span><math><mrow><msub><mi>σ</mi><mi>v</mi></msub></mrow></math></span>, and depends on the <span><math><mrow><msub><mi>σ</mi><mi>v</mi></msub></mrow></math></span> value and the contrast in the elastic moduli between competent and incompetent layers. These findings provide new insights into fracture clustering phenomenon and can serve as a basis for improving its numerical modeling that should be able to reproduce the obtained results.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"196 ","pages":"Article 105392"},"PeriodicalIF":2.6,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143628515","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":"Characteristics and modelling of slip-rate variability and temporal earthquake clustering across a distributed network of active normal faults constrained by in situ 36Cl cosmogenic dating of fault scarp exhumation, central Italy","authors":"Roberts G.P ,&nbsp;Iezzi F ,&nbsp;Sgambato C ,&nbsp;Robertson J ,&nbsp;Beck J ,&nbsp;Mildon Z.K ,&nbsp;Papanikolaou I ,&nbsp;Michetti A.M ,&nbsp;Faure Walker J.P ,&nbsp;Mitchell S ,&nbsp;Meschis M ,&nbsp;Shanks R ,&nbsp;Phillips R ,&nbsp;McCaffrey K.J.W ,&nbsp;Vittori E ,&nbsp;Visini F ,&nbsp;Iqbal M","doi":"10.1016/j.jsg.2025.105391","DOIUrl":"10.1016/j.jsg.2025.105391","url":null,"abstract":"<div><div>We present a compilation of new and unpublished <em>in situ</em> ³⁶Cl cosmogenic isotope data recording the exhumation of 27 active normal fault planes by earthquake slip for the central Apennines, Italy. We do this to constrain the characteristics of slip-rate variability and temporal earthquake clustering and anticlustering across the entire extending orogen, and to assess why it occurs. From the ³⁶Cl observations we report(1) the long-term slip-rates averaged since 20 ka, (2) the percentage of sites with clusters and anticlusters in each 1 kyrs time-slice back to 20 ka, (3) regional maps showing cluster locations for every 1 kyr time-slice, (4) cluster and anticluster durations, and (5) the amounts of slip and slip-rates averaged over the duration of clusters and anticlusters. To study why this slip-rate variability has developed we conduct modelling of stress interactions between faults and underlying shear-zones, and between neighbouring fault/shear-zone structures. We show that the measured slip-rate variability and temporal clustering can be replicated by a model where the transfer of differential stress between faults and their underlying shear-zones, and between neighbouring fault/shear-zone structures, produces changes in strain-rates on underlying viscous shear-zones which drive periods of rapid or reduced slip-rate on their overlying faults. We suggest that stress and hence strain-rate increase on an underlying shear-zone produced by coseismic slip on its overlying fault is the mechanism that initiates an earthquake cluster. Clusters progress because the increased strain-rate on the shear-zone reloads the overlying fault producing a positive feedback loop. The clusters also produce stress reduction on fault/shear-zones located across strike, initiating anticlusters in those locations. The durations of anticlusters will be set by the summed coseismic and interseismic stress changes through time, because although these shear-zones develop relatively low viscous strain-rates, eventually they will load their overlying fault to failure initiating a new cluster. These interactions cause the locations of clusters and anticlusters to migrate across and along-strike within the fault system. Such constraints on the processes producing clustering and anticlustering should allow observations of these phenomena to be included in probabilistic seismic hazard assessments (PSHA), and interpretations of the rheology of deforming continental crust.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"195 ","pages":"Article 105391"},"PeriodicalIF":2.6,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579915","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 3D model and growth pattern of the Longquan Shan fault zone in Sichuan basin, China: Implications for the potential earthquake rupture patterns","authors":"Fang Xu ,&nbsp;Renqi Lu ,&nbsp;Peng Su ,&nbsp;Yann Klinger ,&nbsp;Jinyu Zhang ,&nbsp;Yiduo Liu ,&nbsp;Guanshen Liu","doi":"10.1016/j.jsg.2025.105388","DOIUrl":"10.1016/j.jsg.2025.105388","url":null,"abstract":"<div><div>The fault three-dimensional (3D) structure and growth pattern are fundamental features of an active fault, which provide basic parameters for seismic hazard analysis. The Longquan Shan Fault Zone (LQFZ) is a major active fault, stretching for 200 km in the Sichuan Basin, southwestern China. In this study, we obtain a new, detailed 3D structure model of the LQFZ based on 43 high-resolution seismic reflection profiles. We further quantify the fault heave distribution along the entire LQFZ to understand its growth pattern. We find that the LQFZ contains four major thrust faults and a shallow detachment layer. We obtain 106 displacement values from the seismic profiles and 1963 heave values from the 3D structure model. The heave distribution of the LQFZ contains multiple peaks, indicating that the LQFZ is formed through the linkage of multiple fault segments. The cumulative heave profile of the four faults seems like an isolation fault, which implies the LQFZ has grown coherently since its formation. The maximum displacement and fault length of the four thrust faults show a linear scaling relation, suggesting that the faults grow in a self-similar manner. We also analyze the potential earthquakes on the LQFZ based on the 3D fault model and the fault growth pattern.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"195 ","pages":"Article 105388"},"PeriodicalIF":2.6,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143563686","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":"Assessment of linking damage zones of geological faults through numerical modeling","authors":"Karoline Nunes ,&nbsp;Roberto Quevedo ,&nbsp;Deane Roehl ,&nbsp;Bruno R.B.M. Carvalho","doi":"10.1016/j.jsg.2025.105381","DOIUrl":"10.1016/j.jsg.2025.105381","url":null,"abstract":"<div><div>Assessing damage zones is essential to support strategic decisions that ensure operational efficiency and the safety of exploration and production activities in the oil and gas industry. This study presents a numerical methodology based on the finite element method with rock elastoplastic behavior for predicting the linkage and interaction of damage zones triggered by one, two or more faults at the pre-salt level. First, we use conceptual models to assess the deformation mechanisms in linking damage zones and analyze how the choice of the constitutive model and the relative distances between two faults affect the damage zone prediction. The results show the relative position given by the separation and the overlapping of two faults determine whether extensional or contractional mechanisms form. Furthermore, the analysis must consider more comprehensive models capable of simulating shear compaction for the latter. Then, we applied the methodology in a case study in a pre-salt field aiming to assess interaction damage zones. Seismic data provides the geometry of horizons and fault surfaces while well data brings the type of deformation structures present in fault damage zones. The numerical results indicate the formation of extensional interaction damage zones resulting from a sinistral strike-slip combined with the normal movement of faults. Well data corroborate this finding by indicating the presence of hydraulic breccias. The analysis of both conceptual models and the case study demonstrates that the proposed methodology can be used with industry data to predict the formation of damage zones.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"195 ","pages":"Article 105381"},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550332","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":"Structural control on the Southern Andean Nevados de Chillán geothermal system","authors":"Valentina Mura ,&nbsp;Gloria Arancibia ,&nbsp;John Browning ,&nbsp;David Healy ,&nbsp;Camila López-Contreras ,&nbsp;Diego Morata ,&nbsp;Santiago Maza ,&nbsp;Carlos Cardona","doi":"10.1016/j.jsg.2025.105380","DOIUrl":"10.1016/j.jsg.2025.105380","url":null,"abstract":"<div><div>Detailed structural analysis from representative outcrops is necessary to characterize geothermal reservoir dynamics. Here, we estimate fracture density and intensity, as well as the dimensional properties of individual fault and fracture sets in basement rocks of the Nevados de Chillán Geothermal System. We identified several important structural features that could be responsible for controlling local fluid flow; the high-angle sinistral Las Trancas Fault as well as a series of low-angle reverse faults within the Las Termas-Olla de Mote Fault system. Most fractures identified strike either NE-SW, NNE-SSW, and NNW-SSE. Analysis of fault-slip data, supported by seismicity, indicates the presence of a main transtensional regime with subhorizontal NE-trending σ₁. Structures sub-parallel to the present-day local maximum horizontal stress show significant dilation tendencies, whilst NW-SE fractures are less prone to dilation. NE and E-W high angle faults could be primary conduits facilitating the upward migration of hot fluids from reservoirs within crystalline and fractured rocks. The fracture length distribution was analysed using power law, negative exponential, and log-normal distribution. The power law with a scaling exponent of about −3 provides the best fit to the data. This study advances our understanding of the structural control of the geothermal reservoir and its associated fracture-controlled fluid circulation and thereby improves the prospectivity in the region by quantifying the optimum fracture sets for fluid flow.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"196 ","pages":"Article 105380"},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143654528","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":"Calcite twin stress and strain indicators for various polymineralic rocks and mortars","authors":"Arito Sakaguchi ,&nbsp;Kohei Ando","doi":"10.1016/j.jsg.2025.105369","DOIUrl":"10.1016/j.jsg.2025.105369","url":null,"abstract":"<div><div>This paper proposes new formula to estimate strain and stress of various polymineralic materials in low-temperature elastic condition. Sakaguchi et al. (2011) proposed that the average twin lamellae density (Dtw) (number of twins/mm) depends on the load affecting the entire sample, based on discrete element method simulations and triaxial compression tests in the elastic deformation range. However, their derived relational formula between stress and Dtw, based solely on hard sandstone from the Shimanto accretionary complex in SW Japan, is only applicable to rocks with similar Young's modulus. This study attempted to perform uniaxial compression tests on mortar samples mixed with synthetic calcite grains. The specimens with different Young's modulus from approximately 5.9 to 10 GPa can be made by varying the water/cement ratio using the high strength cement. Calcite synthesized in an autoclave does not contain primary twin lamellae. From the result of the uniaxial compression test, the Dtw increased from 0 to 212/mm. The Dtw depends on the load affecting the entire sample. The rate of increase of Dtw with load varies for specimens with different Young's modulus, but Dtw increases in direct proportion to strain for all specimens regardless of Young's modulus, as represented by:</div><div><span><span><span><math><mrow><mi>ε</mi><mo>=</mo><mn>0.0094</mn><mspace></mspace><mtext>Dtw</mtext><mspace></mspace><mo>–</mo><mspace></mspace><mn>0.20</mn><mspace></mspace><mrow><mo>(</mo><mrow><mo>±</mo><mspace></mspace><mn>0.105</mn></mrow><mo>)</mo></mrow><mtext>,</mtext></mrow></math></span></span></span>where, ε represents shortening strain (%). For a hard specimen without plastic deformation and with a known Young's modulus, the paleo-stress experienced by the specimen can be estimated from the strain obtained from the average Dtw, since elastic strain and stress are proportional. This technique can be used for problems ranging from structural geology to building construction ones at low temperature and elastic strain state.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"194 ","pages":"Article 105369"},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509153","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}