Principal Strain Research Articles

Combining engineering and wood science for the conservation of artworks: Hygro-mechanical study of Mona Lisa’s wooden support

Since 2004, the wooden support of Mona Lisa has been studied by an international research team formed by specialists of wood science and optical measurements, interacting closely with curators and restorers, to evaluate the climatic specifications adopted for the then new climate-controlled display case, assess the risk of propagation of a historical crack affecting the Panel, suggest possible improvements to the Panel’s framing, and improve the technological aspects of the current monitoring procedure. The study has been carried out mainly by direct observation and measurements during the yearly opening of the display case, by continuous monitoring of the Panel’s mechanical behaviour and by developing a predictive numerical model based on the finite element method. This paper deals with the following topics: (i) a technological description of the Panel and of its framing, (ii) the non-invasive measurement equipment and monitoring methods developed, (iii) the simulations of the hygro-mechanical behaviour, (iv) the most significant results obtained so far, including the derivation of the elastic parameters of the wooden Panel, the description of the contact zones between Panel and framing, the evaluation of contact forces and possible actions for improving the framing. The model implementation evidences the correspondence between principal strains in the Panel and craquelure patterns in the paint layers, and allows assessing the crack propagation risk.

Discrete modelling of the mechanical response of Cuxhaven sand under shear and oedometric conditions using the rolling resistance contact model

The Distinct element method (DEM) is a promising approach to model the microscopic behaviour of granular materials, but the capability of the simulations to reproduce the mechanical response of real granular materials depends strongly on the contact model parameters utilized. The present study focuses on the calibration and validation of the rolling resistance linear model parameters for Cuxhaven sand based on the experimental results from triaxial and oedometer tests. A sensitivity analysis was conducted to explore the influence of contact model parameters on the sample preparation and the shear stage of triaxial tests. The influence of parameters like rolling resistance friction coefficient, inter-particle friction coefficient, effective modulus, and normal-to-shear stiffness ratio were investigated. For calibration of the DEM model, the input parameters were selected such that the simulations reproduce the macro mechanical characteristics like dilation angle, peak stress, and stiffness. The calibrated parameters were then validated by simulating a one-dimensional compression test. The results are in good agreement with the experiments, which proves the suitability of the calibrated parameters. In addition, the validated parameters were applied to investigate the mechanical behaviour including the evolution of contact force chains, non-coaxiality of principal stress and strain rate, and sample inhomogeneity during a simple shear test.

Molecular Docking Study of New Pyrrolyl Benzohydrazide Schiff Bases as M. tuberculosis InhA Enzyme Inhibitors

Background Tuberculosis TB is an ancient chronic infectious disease affecting primarily the lungs of humans and rapidly co-evolved with humans since several million years. It is mainly caused by a group of bacterial species termed Mycobacterium tuberculosis a principal strain of this infection. Each second millions are at risk of acquiring new infection of becoming sick prone to death and a conclusive understanding of pathogenesis is still deficient.Objective To design a series of new pyrrole benzohydrazide schiff bases as M. tuberculosis InhA inhibitors.Methods Docking software Sybyl-X version 2.0 was used for molecular modeling. To dock intended compounds Surflex-Dock procedure of sybyl was castoff. M. tuberculosis enoyl reductase InhA inhibitor target protein 4TZK complexed with ligand 1-cyclohexyl-N-3 5-dichlorophenyl-5-oxopyrrolidine3-carboxamide was taken from Protein Data Bank PDB entry code 4TZK httpwww.rcsb.orgpdb.Results Docking scores of the compounds ranged between 5.47 - 3.32 summarizing the interface force field between enzyme and the ligands.Conclusion Sixteen molecules bearing pyrrole hydrazone moiety were docked showing promising M. tuberculosis inhibition activity. In silico molecular docking analysis exhibited that peptide linkage -CO-NH- and imine -CN- of pyrrole hydrazones were important in binding with the targeted receptor.

Effect of the Slenderness Relation on In-Plane Deformation in Stack Compression Tests

In forming technologies and their simulation, knowing the flow curve characteristic of the material is an essential parameter. Acquiring this knowledge is particularly challenging for sheet materials in high strain ranges. It is well-known that friction and geometric relationships have a distorting effect on the flow curves, thus compensation is necessary. However, the geometric ratio can not only influence the formation of the flow curve, if our material shows anisotropic behaviour. In our research, using compression tests, we examined the deformation relations of deformed specimens through digital imaging methods. The stack compression test is widely used to determine the flow curve in a broad range of large deformation. During the test, several disk specimens with the same geometric characteristics were stacked on top of each other to form a final test piece, and then compression tests were conducted on these assemblies. We found that at low values of the geometric ratio (0.1 in our study), the proportion of plastic, planar principal strains indicating anisotropic behaviour is greater than at higher geometric ratios (0.5 and 1.0 in our study).

AI-based denoising of head impact kinematics measurements with convolutional neural network for traumatic brain injury prediction.

Wearable devices are developed to measure head impact kinematics but are intrinsically noisy because of the imperfect interface with human bodies. This study aimed to improve the head impact kinematics measurements obtained from instrumented mouthguards using deep learning to enhance traumatic brain injury (TBI) risk monitoring. We developed one-dimensional convolutional neural network (1D-CNN) models to denoise mouthguard kinematics measurements for tri-axial linear acceleration and tri-axial angular velocity from 163 laboratory dummy head impacts. The performance of the denoising models was evaluated on three levels: kinematics, brain injury criteria, and tissue-level strain and strain rate. Additionally, we performed a blind test on an on-field dataset of 118 college football impacts and a test on 413 post-mortem human subject (PMHS) impacts. On the dummy head impacts, the denoised kinematics showed better correlation with reference kinematics, with relative reductions of 36% for pointwise root mean squared error and 56% for peak absolute error. Absolute errors in six brain injury criteria were reduced by a mean of 82%. For maximum principal strain and maximum principal strain rate, the mean error reduction was 35% and 69%, respectively. On the PMHS impacts, similar denoising effects were observed and the peak kinematics after denoising were more accurate (relative error reduction for 10% noisiest impacts was 75.6%). The 1D-CNN denoising models effectively reduced errors in mouthguard-derived kinematics measurements on dummy and PMHS impacts. This study provides a novel approach for denoising head kinematics measurements in dummy and PMHS impacts, which can be further validated on more real-human kinematics data before real-world applications.

Ultrasound elastography to quantify average percent pressure-normalized strain reduction associated with different aortic endografts in 3D-printed hydrogel phantoms

ObjectiveStrain has become a viable index for evaluating abdominal aortic aneurysm stability after endovascular aneurysm repair (EVAR). In addition, literature has shown that healthy aortic tissue requires a degree of strain to maintain homeostasis. This has led to the hypothesis that too much strain reduction conferred by a high degree of graft oversizing is detrimental to the aneurysm neck in the seal zone of abdominal aortic aneurysms after EVAR. We investigated this in a laboratory experiment by examining the effects that graft oversizing has on the pressure-normalized strain (ερ+¯/pulse pressure [PP]) reduction using four different infrarenal EVAR endografts and our ultrasound elastography technique. Approximate graft oversizing percentages were 20% (30 mm phantom-graft combinations), 30% (28 mm phantom-graft combinations), and 50% (24 mm phantom-graft combinations). MethodsAxisymmetric, 10% by mass polyvinyl alcohol phantoms were connected to a flow simulator. Ultrasound elastography was performed before and after implantation with the four different endografts: (1) 36 mm polyester/stainless steel, (2) 36 mm polyester/electropolished nitinol, (3) 35 mm polytetrafluoroethylene (PTFE)/nitinol, and (4) 36 mm nitinol/polyester/platinum-iridium. Five ultrasound cine loops were taken of each phantom-graft combination. They were analyzed over two different cardiac cycles (end-diastole to end-diastole), yielding a total of 10 maximum mean principal strain (ερ+¯) values. ερ+¯ was divided by pulse pressure to yield pressure-normalized strain (ερ+¯/PP). An analysis of variance was performed for graft comparisons. We calculated the average percent ερ+¯/PP reduction by manufacturer and percent oversizing. These values were used for linear regression analysis. ResultsResults from one-way analysis of variance showed a significant difference in ερ+¯/PP between the empty phantom condition and all oversizing conditions for all graft manufacturers (F(3, 56) = 106.7 [graft A], 132.7 [graft B], 106.5 [graft C], 105.7 [graft D], P < .0001 for grafts A-D). There was a significant difference when comparing the 50% condition with the 30% and 20% conditions across all manufacturers by post hoc analysis (P < .0001). No significant difference was found when comparing the 20% and 30% oversizing conditions for any of the manufacturers or when comparing ερ+¯/PP values across the manufacturers according to percent oversize. Linear regression demonstrated a significant positive correlation between the percent graft oversize and the all-graft average percent ερ+¯/PP reduction (R2 = 0.84, P < .0001). ConclusionsThis brief report suggests that a 10% increase in graft oversizing leads to an approximate 5.9% reduction in ερ+¯/PP on average. Applied clinically, this increase may result in increased stiffness in axisymmetric vessels after EVAR. Further research is needed to determine if this is clinically significant.

Mechanical behavior of recycled FDM printed parts from PETG in the circular economy

The aim of this paper was to observe the behavior of recycled 3D printed polyethylene terephthalate glycol (PETG) specimens and 3D printed raw specimens. In order to extrude the recycled grains into a filament, a Felfil evo filament extruder was used. The recycled filament was extruded from PETG at a temperature of 195°C and with a speed of 7 rpm according to the manufacturers’ requirements. Subsequently, different colors of the raw filament were printed on tensile specimens using Prusa i3 MK3S Original to compare the results between the recycled filament and the manufactured one. After printing the samples, the tensile tests were performed on the Zwick machine, with a capacity of 5KN. For the determination of the strain state in the test specimens, digital image correlation was used. A good correlation between the results was observed. Digital image correlation helped to better understand of the distribution of true principal strain in the recycled and raw specimens.

Contact Pressure Evolution in Heat-Treated Iron-Based Shape Memory Joints

This paper presents an experimental investigation into the behavior of open-ended Fe-based Shape Memory Alloy (Fe-SMA) tubes under biaxial pre-straining conditions, focusing on development of interface contact pressure as a result of the shape memory effect (SME). During the pre-straining process of Fe-SMA tubes, the cross-section undergoes complete inelastic deformation with a non-uniform distribution. Consequently, non-uniform biaxial pre-strain emerges across the cross-section, leading to the formation of stress-induced martensite in both the radial and circumferential directions. This results in the alteration of the SME due to the direction and interaction of biaxial martensite. Consequently, the material experiences a complex pre-strain state, posing challenges in assessing the SME in Fe-SMA tubes. Nevertheless, it is possible to interpret the complex overall SME performance on the basis of measurements of the resultant pressure exerted by the Fe-SMA tube on a substance, thereby limiting its free recovery. This study explores the development of the interface contact pressure highlighting the impact of heat-treatment on the gripping capacity in Fe-SMA tubes. Via coupling of analytical models with results extracted from an experimental campaign, the resultant pressure at the interface throughout the course of activation is quantified aiding to assess the SME performance. The experimental setup involves Fe-SMA and steel tubes enabling the quantification of interface contact pressure through principal strain measurements at the inner diameter of the steel tube, allowing for differentiation of SME performance under as-received and heat-treated conditions.

Thermo-Mechanical Simulation of the Powder Bed of Polyamide 12 during the Selective Laser Sintering Process

The selective laser sintering process is considered to be a new process among the most innovative techniques in the field of additive manufacturing, to facilitate the development and the technical improvement of this process, Thermo-mechanical investigation is necessary to control the SLS process, in this paper a thermo-mechanical simulation of selective laser sintering of polyamide 12 will be presented., this thermo-mechanical simulation was made under the COMSOL Multiphysics software, using Hook's law with the equilibrium and accounting equations for the calculation of the residual stresses appearing in the sintered layer of polyamide 12, this simulation was made for the prevention of deformations appeared in the final printed parts. The calculation of von Mises stress and the calculation of the magnitude of displacement within a sintered layer of polyamide 12 was done, with the analysis of the volumetric strain and the calculation of the volume: stress tensors, principal strain directions.

Biomechanical Study of Three Cannulated Screws Configurations for Femur Neck Fracture: A Finite Element Analysis.

To improve the performance of cannulated screws (CSs) in the treatment of femoral neck fractures (FNF), a number of new screw configurations have been proposed. However, most of the studies have only analyzed the biomechanical performance of different screw configurations under static conditions. This study aimed to investigate the biomechanical performance of three cannulated screws configurations under different loadings through finite element analysis. In this FEA study, nine numerical models of proximal femur were employed to analyze the mechanical response of various fracture types and different fixation strategies (three inverted triangular parallel cannulated screws (TCS), four non-parallel cannulated screws (FCS) and biplane double-supported screw fixation (BDSF) respectively). The maximum principal strain (MPS) on the proximal femur and the von Mises stress on the screws were compared for different models. In Pauwels I and II fractures, FCS had the lowest peak MPS on the proximal femur and the BDSF had highest peak MPS value. In Pauwels III fractures, BDSF performance in MPS is improved and better than FCS under partial loading conditions. FCS exhibits the lowest von Mises stress in all load conditions for all fracture types, demonstrating minimal risk of screws breakage. FCS is an ideal screw configuration for the treatment of FNF. And BDSF has shown potential in the treatment of Pauwels type III FNF.

Finite element modeling and analysis of effect of preexisting cervical degenerative disease on the spinal cord during flexion and extension.

Recent studies have emphasized the importance of dynamic activity in the development of myelopathy. However, current knowledge of how degenerative factors affect the spinal cord during motion is still limited. This study aimed to investigate the effect of various types of preexisting herniated cervical disc and the ligamentum flavum ossification on the spinal cord during cervical flexion and extension. A detailed dynamic fluid-structure interaction finite element model of the cervical spine with the spinal cord was developed and validated. The changes of von Mises stress and maximum principal strain within the spinal cord in the period of normal, hyperflexion, and hyperextension were investigated, considering various types and grades of disc herniation and ossification of the ligamentum flavum. The flexion and extension of the cervical spine with spinal canal encroachment induced high stress and strain inside the spinal cord, and this effect was also amplified by increased canal encroachments and cervical hypermobility. The spinal cord might evade lateral encroachment, leading to a reduction in the maximum stress and principal strain within the spinal cord in local-type herniation. Although the impact was limited in the case of diffuse type, the maximum stress tended to appear in the white matter near the encroachment site while compression from both ventral and dorsal was essential to make maximum stress appear in the grey matter. The existence of canal encroachment can reduce the safe range for spinal cord activities, and hypermobility activities may induce spinal cord injury. Besides, the ligamentum flavum plays an important role in the development of central canal syndrome.Significance.This model will enable researchers to have a better understanding of the influence of cervical degenerative diseases on the spinal cord during extension and flexion.

Identification of thermo-viscoplastic behavior for AA6061 under in-plane biaxial loadings

This work aims to investigate the thermo-visco-plastic behavior of an aluminum alloy (AA6061) sheet metal submitted to in-plane biaxial loadings under warm conditions. Biaxial tensile tests are performed in a temperature range from room temperature to 160 °C, and in a strain rate range from quasi-static to the so-called “intermediate” strain rate (up to few s−1). The specimen shape used in this study has been previously defined and validated by the authors to identify the viscoplastic hardening models of metallic alloys at large strains. A specific device leading to a uniform temperature in the sample is associated with a dynamic biaxial traction bench to carry out the temperature and strain rate dependent characterizations. From these experiments, both the experimental forces measured on each axis of the in-plane biaxial specimen and the principal strains at the center of the specimen are obtained. These experimental data are then used in an inverse analysis loop, based on a finite element model of the biaxial test, to calibrate the parameters of a thermo-viscoplastic strain hardening model by minimizing the difference between the experimental and numerical principal strains at the center point of the specimen. Finally, it is shown that the identified hardening model well predicts the flow stress of AA6061 under different temperatures and strain rates for a strain level of up to 40%.

Epigallocatechin gallate-immobilized antimicrobial resin with rechargeable fluorinated synergistic composite for enhanced caries control

ObjectivesGiven the global prevalence of dental caries, impacting 2.5 billion individuals, the development of sophisticated prevention filling materials is crucial. Streptococcus mutans, the principal caries-causing strain, produces acids that demineralize teeth and initiate dental caries. To address this issue, we aimed to develop a synergistic resin-based composite for enhancing caries control. MethodsThe synergistic resin composite incorporates fluorinated kaolinite and silanized Al2O3 nanoparticle fillers into an epigallocatechin gallate (EGCG) immobilized urethane-modified epoxy acrylate (U-EA) resin matrix, referred to the as-prepared resin composite. The EGCG-modified TPGDA/U-EA network was synthesized by preparing methacrylate-functionalized isocyanate (HI), reacting it with EGCG to form HI-EGCG, and then incorporating HI-EGCG into the TPGDA/U-EA matrix. The lamellar space within the kaolinite layer was expanded through the intercalation of acrylamide into kaolinite, enhancing its capability to adsorb and release fluoride ions (F–). The layered structure of acrylamide/ kaolinite in the U-EA resin composite acts as a F– reservoir. ResultsThe physico-mechanical properties of the as-prepared resin composites are comparable to those of commercial products, exhibiting lower polymerization shrinkage, substantial F– release and recharge and favorable diametral tensile strength. The immobilized EGCG in the composite exhibits potent antimicrobial properties, effectively reducing the biofilm biomass. Furthermore, the synergistic effect of EGCG and fluorinated kaolinite efficiently counteracts acid-induced hydroxyapatite dissolution, thereby suppressing demineralization and promoting enamel remineralization. SignificanceOur innovative EGCG and fluoride synergistic composite provides enhanced antimicrobial properties, durable anti-demineralization, and tooth remineralization effects, positioning it as a promising solution for effective caries control and long-term dental maintenance.

Automated 3-D Ultrasound Elastography of the Breast: An In Vivo Validation Study

Studies have indicated that adding 2-D quasi-static elastography to B-mode ultrasound imaging improved the specificity for malignant lesion detection, as malignant lesions are often stiffer (increased strain ratio) compared with benign lesions. This method is limited by its user dependency and so unsuitable for breast screening. To overcome this limitation, we implemented quasi-static elastography in an automated breast volume scanner (ABVS), which is an operator-independent 3-D ultrasound system and is especially useful for screening women with dense breasts. The study aim was to investigate if 3-D quasi-static elastography implemented in a clinically used ABVS can discriminate between benign and malignant breast lesions. Volumetric breast ultrasound radiofrequency data sets of 82 patients were acquired before and after automated transducer lifting. Lesions were annotated and strain was calculated using an in-house-developed strain algorithm. Two strain ratio types were calculated per lesion: using axial and maximal principal strain (i.e., strain in dominant direction). Forty-four lesions were detected: 9 carcinomas, 23 cysts and 12 other benign lesions. A significant difference was found between malignant (median: 1.7, range: [1.0-3.2]) and benign (1.0, [0.6-1.9]) using maximal principal strain ratios. Axial strain ratio did not reveal a significant difference between benign (0.6, [-12.7 to 4.9]) and malignant lesions (0.8, [-3.5 to 5.1]). Three-dimensional strain imaging was successfully implemented on a clinically used ABVS to obtain, visualize and analyze in vivo strain images in three dimensions. Results revealed that maximal principal strain ratios are significantly increased in malignant compared with benign lesions.

CT measurement of damage characteristics of meso-structure of freeze-thawed granite in cold regions and preliminary exploration of its mechanical behavior during a single freeze-thaw process

Abstract The freeze-thaw (FT) damage characteristics of granite after different FT cycles were studied using computed tomography (CT) images. The three-dimensional (3D) volume numbers in the image were extracted to obtain the 3D pore structure of representative volume elements (RVEs) of granite under different FT cycles. The CT images of granite after 80 FT cycles were selected to draw reference lines for quantitative analysis of the distribution of meso-cracks in granite after FT cycles. Subsequently, a finite element model was established to explore the mechanical properties of minerals in granite during a single FT process. The results show that the FT damage inside the granite exhibits fracture characteristics, and the number of internal cracks, cracks area, and voxel porosity increase with the increase of FT cycles. After 80 FT cycles, the distribution of meso-cracks on the cross-section of granite exhibits significant anisotropy, and the distribution density and variation coefficient of meso-cracks vary with the dip direction angle of the reference line. The maximum principal stress and strain in the finite element model are negatively related to temperature. The maximum principal stress and strain of biotite minerals are consistently higher than those of feldspar and mica during FT cycles. The results can provide a reference for exploring the internal mechanism of the weakening of mechanical properties of granite microstructure caused by FT damage in cold regions.

Assessment of seismic behavior of historical masonry cupolas: Case of Emir Saltuk Cupola

The protection of historical masonry structures against earthquakes requires a comprehensive understanding of their nonlinear behavior; including damage and collapse mechanisms. Throughout history and in present times, these structures have undergone multiple strengthening interventions to enhance their seismic resilience. In this context, the utilization of nonlinear analysis on 3D finite element models has become a common and reliable approach. This article focuses on the seismic performance of historical Emir Saltuk Cupola of Erzurum city which is recognized as a cultural asset by the Ministry of Tourism and Culture of the Republic of Türkiye. Emir Saltuk Cupola is a rare work built in the 12th century as a monumental grave for the founder of Saltuklu Government. The study specifically examines the impact of a reinforced concrete pulley and dome, previously added to the cupola for the purposes of seismic strengthening, on its seismic behavior, force-displacement capacity, and collapse mechanism. Determining the seismic behavior of the structure is aimed to create an important reference for cupola structures, which are frequently encountered in the Turkish-Islamic geography. Notably, this study marks the first instance where advanced numerical simulation methods have been employed to analyses the cupola. Additionally, no prior research has been conducted to assess the propagation of damage and collapse mechanisms within this type of structure. Finite element model of the structure was developed considering the architectural characteristics of the cupola. The model was calibrated based on the findings of operational modal analysis. Nonlinear dynamic analyses were performed using ground motion records from significant earthquakes, including the 1992 Erzincan, 1995 Kobe and 2023 Kahramanmaraş earthquakes, to study the seismic behavior and collapse mechanisms of the cupola. The study evaluated the reinforced concrete pulley and dome in terms of maximum principal strains, maximum displacements, crack distributions, and failure mechanisms of the cupola. The reinforced concrete elements added to the structure in previous years, while assisting in a significant increase in strength capacity, did not contribute significantly to displacement capacity of the masonry. Additionally, it has been determined that under strong ground motions, these elements completely alter the collapse mechanism of the structure, leading to damage in the reinforced concrete elements and thus helping to prevent complete collapse. The findings highlight the substantial impact that strengthening interventions may be altering the seismic behavior of historical structures. Overall, this research contributes to our understanding of the seismic performance of historical masonry cupolas and emphasizes the importance of accurately assessing their behavior through advanced numerical simulations which are supported by in-situ experimentation.

Characteristic analysis of bionic-induced structures with negative stiffness inspired by the growth and deformation differences of branches

Negative stiffness (NS) structures with curved beams easily experience beam fracture in small-scale designs, limiting their repeatability and energy absorption. The induced energy absorption structure (IEAS), which achieves negative stiffness by altering load transfer paths, is designed inspired by the growth and deformation of tree branches. By means of the variation method of geometric parameters, a unique asymmetric buckling deformation mode is realized in IEAS. The NS and energy absorption characteristics in IEAS are analyzed based on load distribution and major principal strain theory. Compression results demonstrate that the asymmetric buckling mode exhibits higher energy absorption and specific energy absorption compared to symmetric linear buckling, effectively improving structural toughness. Through gradient analysis of geometric parameters and comprehensive analysis of induced structure layouts, the asymmetric buckling mode is successfully implemented in multi-layer IEAS. The multi-layer IESA exhibits excellent ability of energy absorption and toughness, making it have potential applications in areas that require small-sized designs with high energy absorption capabilities.

Estimation of the Effects of Achilles Tendon Geometry on the Magnitude and Distribution of Local Strain: A Finite Element Analysis

We investigated the influence of Achilles tendon (AT) geometry on local-strain magnitude and distribution during loading, using finite element analysis. We calculated the following eight AT parameters for 18 healthy men: thickness and width of the most distal part, minimum cross-sectional area (mCSA), and most proximal part; length; and position of the mCSA. To investigate the effect of AT geometry on the magnitude and distribution of local strain, we created three-dimensional numerical models by changing the AT parameter values for every one standard deviation (SD) in the range of ±2 SD. A 4000 N lengthening force was applied to the proximal surface of all the models. The mean first principal strain (FPS) was determined every 3% of the length. The highest FPS in each model was mainly observed in the proximal regions; the 86–89% site (the most proximal site was set at 100%) had the highest number of models with the highest FPS (nine models). The highest FPS was observed in the model with a distal thickness of −2 SD, which was 27.1% higher than that of the standard model observed in the 2–5% site. Therefore, the AT geometry influences local-strain magnitude and distribution during loading.

Present-day crustal movement and seismic moment balance on major active faults around the easternmost segment of the Kunlun fault, Tibetan Plateau, China

After the 2021 Ms 7.4 Madoi, China earthquake located south of the eastern Kunlun fault, the coseismic Coulomb stress changes show that the earthquake potential is enhanced towards the easternmost segment of the Kunlun fault. Before the 2008 Mw 7.9 Wenchuan, China earthquake, the easternmost segment of the Kunlun fault is considered to being a region with the highest frequency occurrence of moderate-to-strong earthquakes in mainland China, where there are still at least three seismic gaps at present, indicating an urgent earthquake hazard. The tectonic deformation pattern is closely related to the development and occurrence of earthquakes. In this study, we collect all the available GPS data to obtain a crustal movement velocity field with high precision and high resolution by removing nontectonic effects within the study area. The GPS velocity profile and two-dimensional strain rates are then derived from the updated GPS velocities to analysis the characteristics of crustal deformation. Our results demonstrate that the Longriba fault zone slips predominantly right-laterally with the rate of 5.2 ± 0.5 mm/yr and the crustal shortening rate is ∼0.5 mm/yr across the Longriba and Longmenshan faults. Along with notable crustal extension and contraction, the principal strain rate field is distributed in a wide area on the northwest part of the Longmenshan fault, and decreases southwestward along the Longmenshan fault zone. In addition, we provide the time series of 8 campaign GPS stations which have never been published before. Moreover, the moment deficit estimate is a well-established way of assessing the earthquake hazard at a specific fault. Accompanying with the inverted slip rates and locking depth, we estimate the rates of moment accumulation on major faults and compare them with the seismic moment released on each fault derived from the Chinese historical earthquake catalog which extends for more than 2000 years in many regions. We find that the moment deficit is mainly concentrated on the Longriba fault with a value of 4.18 × 1017 Nm/yr. The Longriba fault have accumulated enough seismic energy to generate one Mw > 7.7 earthquake on it, or two Mw > 7.5 earthquakes on its two branches in the future. This study is an essential indicator for understanding the present-day tectonic deformation pattern in the Tibetan Plateau and is also helpful for seismic hazard assessment.

Present-day crustal deformation based on GPS measurements in southeastern Tibetan Plateau: implications for geodynamics and earthquake hazard

GPS-derived strain rates can provide a tight constraint in understanding tectonic evolution of the Tibetan Plateau and are helpful in seismic hazard assessment. For this purpose, we at first verify the method, proposed by Zhu et al. in 2005 and 2006, for the computation of the strain rates, and found that the approach is reasonable and accurate. Then, based on the updated GPS data, we compute strain rates in southeastern Tibetan Plateau (SETP). The computed results showed that the strain rates in the Sichuan Basin and South China Block are very small, and the high values are largely concentrated along the Sagaing Fault and Xianshuihe-Anninghe-Xiaojiang fault system. In addition, the highest principal strain rates are located around the eastern Himalayan syntaxis (EHS), with the compressive orientations perpendicular to the Main Thrust Belt. In particular, the calculated extensive deformation basically matches the normal faulting earthquakes. In general, the characteristic of the strain rate distribution is in good agreement with the tectonic structures from the geological and geophysical investigations. At last, according to the strain rates, seismicity, and tectonic structures, we estimate five most likely zones for future major earthquakes in SETP. These areas include the Zemuhe Fault, northwestern segment of the Red River Fault, and at the intersection between the Ganzi-Yushu Fault and the Xianshuihe Fault, and at the one between the Zhongdian Fault and Jinshajiang Fault. Consequently, this study is significant in deep understanding of the geodynamics in the Tibetan Plateau and earthquake hazard assessment.