Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar a...Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.展开更多
In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock...In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.展开更多
Fault sealing capacity is controlled by present-day geometry and clay content,with current research focusing on enhancing the accuracy of capacity estimates.The mechanisms for evaluating both presentday and paleo-seal...Fault sealing capacity is controlled by present-day geometry and clay content,with current research focusing on enhancing the accuracy of capacity estimates.The mechanisms for evaluating both presentday and paleo-sealing are consistent,where the current sealing capacity representing the final stage in the evolutionary process of fault sealing.To address the limitations of the conventional shale gouge ratio(SGR)in evaluating the dynamic nature of fault sealing,this study proposes a visual model for fault sealing evolution.Fault sealing evolution is jointly controlled by the burial history and clay smear history and exerts a critical influence on hydrocarbon migration and accumulation.Hydrocarbon exploration data confirm that fault sealing during and after hydrocarbon migration critically impacts reservoir preservation.If faults remain unsealed during hydrocarbon migration and accumulation,they serve solely as conduits,with their present-day sealing capacity having limited impact.Effective fault sealing thus depends on the alignment between the evolutionary sealing stages and hydrocarbon activity.Building on this framework,we propose a method to visually and quantitatively characterize the fault sealing evolution alongside hydrocarbon activity.A case study of the Xishanyao Formation in the Houxia Basin highlights that the F4 fault transitioned from being over-open to sealed at the onset of hydrocarbon migration,thereby preserving the trap,while the F8-2 fault underwent a complete sealed–reopen cycle,with the late-stage reopening leading to an absence of hydrocarbon accumulation.This temporal contrast forms the basis for a new time-sensitive methodology for assessing fault-seal integrity in complex structural settings.展开更多
The Yingxiu-Beichuan fault zone(YBFZ)has long been active and experienced repeated large earthquakes.The physicochemical properties of the deep fault zone(>1000 m)are the key to understanding the deformation mechan...The Yingxiu-Beichuan fault zone(YBFZ)has long been active and experienced repeated large earthquakes.The physicochemical properties of the deep fault zone(>1000 m)are the key to understanding the deformation mechanism of large earthquakes.This study uses rock magnetic,microstructural,and geochemical analyses of representative samples exposed in FZ1681 within the Wenchuan Earthquake Fault Scientific Drilling borehole 2(WFSD-2)cores.Fault gouge and fault breccia have higher magnetic susceptibility values than wall rocks,and they contain abundant paramagnetic minerals and small quantities of magnetite and monoclinic pyrrhotite.The magnetite and monoclinic pyrrhotite in the fault gouge were mainly formed by coseismic frictional heating,indicating that large earthquakes with frictional heating temperatures of~500-900℃once occurred in the YBFZ.The seismogenic and coseismic environment was reducing with a relatively high sulfur content.The monoclinic pyrrhotite in the fault breccia was formed mainly by low-temperature hydrothermal fluid.This indicates that the fault zone experienced reducing and low-temperature(<400℃)hydrothermal fluid with a relatively high sulfur content after the earthquake.The YBFZ,which experiences frequent large earthquakes,is weakly oxidizing environment at different depths,but the effect of the low-temperature hydrothermal fluid is weaker at depth.展开更多
Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this stud...Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.展开更多
The stress-dilatancy relation is important for understanding fault mechanics and brittle deformation of rocks,and hence the onset of frictional instability.The principle of minimum energy ratio was proposed by Rowe,an...The stress-dilatancy relation is important for understanding fault mechanics and brittle deformation of rocks,and hence the onset of frictional instability.The principle of minimum energy ratio was proposed by Rowe,and this Rowe’s theory has been applied to deformation of granular materials.Rowe suggested that the energy ratio,which is the ratio of the energy dissipation rate to energy supply rate,would be a minimum and constant value.The relation between the rate of dilatancy and the maximum stress ratio can be extended to the case of a random assembly of irregular particles whereby the rate of internal work absorbed in frictional heat is a minimum as the mass dilates.According to Rowe’s law.展开更多
Stick slip and stable creep are two principal modes of fault motion. The formeris considered to be closely related to earthquake generation. The determination of themode of motion during geologic time along a fault ou...Stick slip and stable creep are two principal modes of fault motion. The formeris considered to be closely related to earthquake generation. The determination of themode of motion during geologic time along a fault outcropped on earth surface is ofcritical importance to the assessment of the behaviour of fault activity.展开更多
The Archean buried-hill metamorphic reservoirs in the Bohai Bay Basin are examples of metamorphic rocks having faults with diverse strikes as a consequence of multi-phase tectonic evolution.For faults in metamorphic r...The Archean buried-hill metamorphic reservoirs in the Bohai Bay Basin are examples of metamorphic rocks having faults with diverse strikes as a consequence of multi-phase tectonic evolution.For faults in metamorphic rocks,no method that accounts for the properties of metamorphic rocks exists for evaluating fault sealing capacity.To elucidate the mechanisms controlling sealing capacity,our study pioneers a novel methodology termed the Mylonite Gouge Ratio(MGR)method.This method integrates neutron density log responses,petrophysical characteristics,and corresponding depth-specific rock thin-section analyses to assess lateral fault sealing capacity.Application of this set of rules and procedures to metamorphic faults in the basin's Archean strata reveals two critical findings:spatially,the Block X exhibits elevated MGR values indicative of superior sealing efficiency;temporally,Yanshanian NE-trending faults demonstrate enhanced sealing capacity compared to Himalayan EW-trending counterparts,with pre-Yanshanian and syn-Yanshanian tectonic activities facilitating paleo-fluid migration while current sealing conditions favor hydrocarbon preservation.The new method provides a tailored framework for evaluating fault sealing in metamorphic rocks,where conventional methods designed for sedimentary sequences are often inapplicable.This study establishes a new theoretical model for fault-sealing analysis in complex metamorphic reservoirs,with implications for deep hydrocarbon exploration and development.展开更多
The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely asso...The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely associated with induced seismic events.The present study was conducted to examine the role of halite in frictional properties.To this end,laboratory measurements were taken for simulated fault gouge composed of halite.Slide-hold-slide(SHS)shear experiments were performed on gouges with grain size<106 mm at constant normal stress from 5 MPa to 30 MPa and constant shear velocity in the range of 1-10 mm/s.Halite gouge shows higher frictional strength and frictional healing rate than most minerals.The results reveal that the fault within halite can potentially generate intense seismic events and more significant aftershocks.An increase in normal stress leads to a reduction in frictional healing,with frictional strength initially increasing and then decreasing.The elevated shear velocity following fault activation facilitates fault dilation,diminishes the frictional strength of the fault,and contributes to fault healing during the inter-seismic period.The aforementioned findings will contribute to a comprehensive understanding of the potential for the healing property of induced seismicity on faults containing halite,particularly in the Changning region of China.展开更多
Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margi...Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.展开更多
During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the anal...During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the analysis of the metal liquid film formation at the armature/rail contact interface.1D and 3D models are developed based on the characteristic relational equation obtained from the melt liquid film model.These models incorporate thermodynamic equilibrium phase diagram,transient heat and mass transfer model,copper-aluminum alloy reaction model,nonlinear electrical conductivity relational equation and nonlinear thermal conductivity relational equation to analyze the temperature distribution and copper-aluminum intermetallic compounds(Cu-Al IMCs)formation in the melt liquid film.The wear mechanism and influence law of armature are explained in detail from different perspectives to un-derstand and predict the transition and gouging phenomena at the contact interface.The model's validity is confirmed by the results of electromagnetic launch experiments,providing insights for future structure design and material selection of the armature and rail.展开更多
This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdev...This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdeveloped dynamic shear apparatus,and the effects of normal load oscillation amplitude,normal load oscillation period and sliding velocity were studied.The test results reveal that the shear response can be divided into three stages over a whole loading-unloading process,characterized by different time spans and stress variations.Generally,a smaller oscillation amplitude,a longer oscillation period and a fast shear velocity promote the stability of the friction system,which is also confirmed by the Coulomb failure criterion calculated based on the observed periodic apparent friction coefficient.The dynamic strengthening/weakening phenomenon is dependent on the oscillation amplitude and product of sliding velocity and oscillation period(vT).Also,the rate and state friction law incorporating the parameter a that characterizes the normal stress variation is employed to describe the dynamic friction coefficient but exhibits an incompetent performance when handling intensive variation in normal stress.Finally,the potential seismicity induced by oscillating normal stress based on the observed stress drop is analyzed.This work helps us understand the sliding process and stability evolution of natural faults,and its benefits for relative hazard mitigation.展开更多
This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of min...This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of mineralogy on gouge dilation and frictional strength,stability,and healing.Specifically,velocity-stepping and slide-hold-slide experiments were performed in a double direct shear configuration to analyze frictional constitutive parameters at room temperature,under normal stresses of 10,20,and 40 MPa.Gouge dilation was measured based on the applied step-wise changes in shear velocity.The frictional response of the quartz–smectite mixtures and powdered natural rocks are affected by their phyllosilicate content.Frictional strength and healing rates decrease with increasing phyllosilicate content,and at 20 wt.%a transition from velocity-weakening to velocity-strengthening behavior was noted.For both suites of gouges,dilation is positively correlated with frictional strength and healing rates,and negatively correlated with frictional stability.Changes in the permeability of gouge-filled faults were estimated from changes in mean porosity,indexed through measured magnitudes of gouge dilation.This combined analysis implies that the reactivation of caprock faults filled with phyllosilicaterich gouges may have a strong influence on permeability evolution in caprock faults.展开更多
The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus t...The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus that allows direct shear of samples under coupled hydro-mechanical conditions.Velocitystepping(VS)and slide-hold-slide(SHS)experiments are performed on both bare and gouge-bearing surfaces of Xiashan basalt subjected to cyclic shear velocities at 1e30 mm/s,effective normal stresses of 1e5 MPa,and pore pressures of 70e300 kPa.The measured basalt friction coefficients are in the range of 0.67e0.74,which is sensitive to gouge thickness,normal stress,and water.Specifically,a reduction in friction coefficient is observed with an increment in gouge thickness,normal stress,and pore pressure.Based on the microscopic observation of the pre-and post-shearing sliding surfaces,this weakening effect in friction coefficient can be attributed to powder lubrication.Furthermore,the VS test results reveal predominantly velocity-strengthening behavior at investigated slip velocities,and this velocity strengthening behavior does not appear to be influenced by variations in normal stress,gouge thickness,and water.However,changes in sliding velocity and normal stress can lead to a shift between stable and unstable sliding.Specifically,stable sliding is favored by high sliding velocities and low normal stress applied in this study.Finally,we analyze the experimental data by calculating the rate-and-state parameters using the rate-and state-dependent friction(RSF)theory.Importantly,the calculated friction rate parameter(a-b)supports the velocity-strengthening behavior.Both frictional relaxation(Dmc)during hold periods and frictional healing(Dm)upon re-shearing are linearly proportional to the logarithmic hold time,which may be attributed to the growth in true contact area with hold time.This study sheds light on the roles of sliding velocity,and gouge thickness in controlling frictional strength and stability of basalt fractures.展开更多
Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than th...Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than those of soils or rocks due to its high heterogeneity and low strength.Therefore,to improve the accuracy of analysis results,we conducted simple regression analysis and structural equation model analysis and selected major influential factors of friction characteristics among many factors,and then we deduced advanced regression model with the highest coefficient of determination(R^(2)) via multiple regression analysis.Whereas most coefficients of determination in simple regression analysis are below0.3-0.4,coefficient of determination in multiple regression analysis is remarkably large as 0.657.展开更多
Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and ...Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and further induce rupture propagation and earthquakes.In this study,we carried out a laboratory experiment to investigate the fluid-induced slip behavior of fault filled with gouge.The friction evolution characteristic associated with fluid pressure and effective stress was investigated during the slip process.In addition,the role transformation process of the gouge on the slip behavior of fault was revealed.The experimental result indicates that the friction on the filled fault surface is significantly affected by fault gouge.The rupture of the gouge promotes fault slip and the fluid pressure plays a vital role in the initiation of fault slip.The fault gouge enhances the shearing strength of the fault and acts as a barrier before the initial slip under fluid injection.Nevertheless,the fault gouge would accelerate the fault slip and transform into lubricant after the initial slip.展开更多
Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion w...Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.展开更多
The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new ins...The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new insights into the ongoing debate about the frictional strength of brittle fault(Haines and van der Pluijm,2012).However,neither the conditions nor the processes which展开更多
K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite p...K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite polytypes are critical to acquiring K-Ar isotope data for authigenic clays.In this respect,we compared the commonly used clay size separation method through centrifugation with vacuum filtration technology,showing that the former is prone to extract fractions with finer particle sizes under similar conditions,thus improving the error in the authigenic end-member age.Additionally,we demonstrated that the side-packed mounting method for X-ray diffraction analysis can significantly enhance the randomness in powder samples,thus improving the quantification accuracy compared with the front-packed and back-packed methods.The validity of our quantification method was confirmed by comparing Profex■modeling patterns with a suite of synthetic mixtures of known compositions,yielding an average analytical error of 3%.Dating results of these artificial mixtures and the reference materials indicated that a large range in percentages of detrital illite and a sufficient amount of age data will produce reliable results for ages of both extrapolated end-members.However,if the range is limited,the extrapolated age close to those of datasets is still reliable.展开更多
A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the specia...A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the special result of fault motion while extruding or grinding. Based on the field investigation, collected from Bailongjiang fault system of Western Qinling Orogenic (QO) Belt, 44 samples of fault gouge were for quartz micro-morphology observation and statistics by the field emission SEM, and 14 samples were tested by thermo-luminescence dating. The results showed that most of the micro-morphology of quartz grains are fish scale and orange-haut fractures, but a small amount of moss-like, stalactitic, and subconchoidal fractures. Also very few decay of quartz grains and typical conchoids fracture quartz grains can be seen. This implied that the Bailongjiang fault system was motioned repeatedly in Quaternary period but main motion period was Pleistocene. 14 thermo-luminescence dating values showed herewith two groups as 343.29-184.06 ka and 92.18-13.87 ka. Therefore, the conclusions can be reached that the fault system were motioned starting at Pliocene epoch, frequently in the middle of Pleistocene (343.29-184.06 ka), and peak frequency in late Pleistocene (92.18-13.87 ka). The fault system motions have stopped at Holocene. The results are significant for the natural disaster risk evaluation in western QO region.展开更多
基金financially supported by the Vietnam National Foundation for Science and Technology Development(NAFOSTED) under grant number 105.032011.11 to Bui Hoang Bac
文摘Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.
文摘In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.
基金funded by the Project of Xinjiang University of Technology(No.2025XQYM044)PetroChina Coalbed Methane Company Project(No.WK23020DG04)。
文摘Fault sealing capacity is controlled by present-day geometry and clay content,with current research focusing on enhancing the accuracy of capacity estimates.The mechanisms for evaluating both presentday and paleo-sealing are consistent,where the current sealing capacity representing the final stage in the evolutionary process of fault sealing.To address the limitations of the conventional shale gouge ratio(SGR)in evaluating the dynamic nature of fault sealing,this study proposes a visual model for fault sealing evolution.Fault sealing evolution is jointly controlled by the burial history and clay smear history and exerts a critical influence on hydrocarbon migration and accumulation.Hydrocarbon exploration data confirm that fault sealing during and after hydrocarbon migration critically impacts reservoir preservation.If faults remain unsealed during hydrocarbon migration and accumulation,they serve solely as conduits,with their present-day sealing capacity having limited impact.Effective fault sealing thus depends on the alignment between the evolutionary sealing stages and hydrocarbon activity.Building on this framework,we propose a method to visually and quantitatively characterize the fault sealing evolution alongside hydrocarbon activity.A case study of the Xishanyao Formation in the Houxia Basin highlights that the F4 fault transitioned from being over-open to sealed at the onset of hydrocarbon migration,thereby preserving the trap,while the F8-2 fault underwent a complete sealed–reopen cycle,with the late-stage reopening leading to an absence of hydrocarbon accumulation.This temporal contrast forms the basis for a new time-sensitive methodology for assessing fault-seal integrity in complex structural settings.
基金supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(2024ZD1000500)the National Natural Science Foundation of China(42172262 and 42372266)+1 种基金the China Geological Survey(DD20240041)the Fundamental Research Funds of the Institute of Geomechanics(DZLXJK202516).
文摘The Yingxiu-Beichuan fault zone(YBFZ)has long been active and experienced repeated large earthquakes.The physicochemical properties of the deep fault zone(>1000 m)are the key to understanding the deformation mechanism of large earthquakes.This study uses rock magnetic,microstructural,and geochemical analyses of representative samples exposed in FZ1681 within the Wenchuan Earthquake Fault Scientific Drilling borehole 2(WFSD-2)cores.Fault gouge and fault breccia have higher magnetic susceptibility values than wall rocks,and they contain abundant paramagnetic minerals and small quantities of magnetite and monoclinic pyrrhotite.The magnetite and monoclinic pyrrhotite in the fault gouge were mainly formed by coseismic frictional heating,indicating that large earthquakes with frictional heating temperatures of~500-900℃once occurred in the YBFZ.The seismogenic and coseismic environment was reducing with a relatively high sulfur content.The monoclinic pyrrhotite in the fault breccia was formed mainly by low-temperature hydrothermal fluid.This indicates that the fault zone experienced reducing and low-temperature(<400℃)hydrothermal fluid with a relatively high sulfur content after the earthquake.The YBFZ,which experiences frequent large earthquakes,is weakly oxidizing environment at different depths,but the effect of the low-temperature hydrothermal fluid is weaker at depth.
基金financial support from the National Key Research and Development Program(Grant No.2024YFA1209801)the National Natural Science Foundation of China(Grant Nos.12302140,12325204)+4 种基金the China Postdoctoral Science Foundation(Grant No.2023M732794)the Fundamental Research Funds for the Central Universities of China(Grant No.sxzy012023213)the Scientific Research Program of Shaanxi Province(Grant No.2023JC-XJ-02)the Young Talent Support Program of Xi'an Science and Technology Association(Grant No.959202413069)Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(Grant No.GZB20230575)。
文摘Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.
基金funded by a Grantin-Air for Scientific Research(24244077).
文摘The stress-dilatancy relation is important for understanding fault mechanics and brittle deformation of rocks,and hence the onset of frictional instability.The principle of minimum energy ratio was proposed by Rowe,and this Rowe’s theory has been applied to deformation of granular materials.Rowe suggested that the energy ratio,which is the ratio of the energy dissipation rate to energy supply rate,would be a minimum and constant value.The relation between the rate of dilatancy and the maximum stress ratio can be extended to the case of a random assembly of irregular particles whereby the rate of internal work absorbed in frictional heat is a minimum as the mass dilates.According to Rowe’s law.
文摘Stick slip and stable creep are two principal modes of fault motion. The formeris considered to be closely related to earthquake generation. The determination of themode of motion during geologic time along a fault outcropped on earth surface is ofcritical importance to the assessment of the behaviour of fault activity.
基金supported by the National Natural Science Foundation of China(Grant Nos.42488101,42302146,U20B6001,42141021)the Peking University-BHP Carbon and Climate Wei-Ming PhD Scholars Program(WM202503)+1 种基金the Program of China Scholarship Council(Grant No.202506010121)the 2024 AAPG Foundation Grants-in-Aid,and China National Petroleum Corporation&Peking University Basic Research Project(JTGS2022JS327).
文摘The Archean buried-hill metamorphic reservoirs in the Bohai Bay Basin are examples of metamorphic rocks having faults with diverse strikes as a consequence of multi-phase tectonic evolution.For faults in metamorphic rocks,no method that accounts for the properties of metamorphic rocks exists for evaluating fault sealing capacity.To elucidate the mechanisms controlling sealing capacity,our study pioneers a novel methodology termed the Mylonite Gouge Ratio(MGR)method.This method integrates neutron density log responses,petrophysical characteristics,and corresponding depth-specific rock thin-section analyses to assess lateral fault sealing capacity.Application of this set of rules and procedures to metamorphic faults in the basin's Archean strata reveals two critical findings:spatially,the Block X exhibits elevated MGR values indicative of superior sealing efficiency;temporally,Yanshanian NE-trending faults demonstrate enhanced sealing capacity compared to Himalayan EW-trending counterparts,with pre-Yanshanian and syn-Yanshanian tectonic activities facilitating paleo-fluid migration while current sealing conditions favor hydrocarbon preservation.The new method provides a tailored framework for evaluating fault sealing in metamorphic rocks,where conventional methods designed for sedimentary sequences are often inapplicable.This study establishes a new theoretical model for fault-sealing analysis in complex metamorphic reservoirs,with implications for deep hydrocarbon exploration and development.
基金supported by the National Key Research and Development Project(Grant No.2023YFE0110900)the National Natural Science Foundation of China(Grant Nos.42320104003 and 42077247).
文摘The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely associated with induced seismic events.The present study was conducted to examine the role of halite in frictional properties.To this end,laboratory measurements were taken for simulated fault gouge composed of halite.Slide-hold-slide(SHS)shear experiments were performed on gouges with grain size<106 mm at constant normal stress from 5 MPa to 30 MPa and constant shear velocity in the range of 1-10 mm/s.Halite gouge shows higher frictional strength and frictional healing rate than most minerals.The results reveal that the fault within halite can potentially generate intense seismic events and more significant aftershocks.An increase in normal stress leads to a reduction in frictional healing,with frictional strength initially increasing and then decreasing.The elevated shear velocity following fault activation facilitates fault dilation,diminishes the frictional strength of the fault,and contributes to fault healing during the inter-seismic period.The aforementioned findings will contribute to a comprehensive understanding of the potential for the healing property of induced seismicity on faults containing halite,particularly in the Changning region of China.
基金supported by the research grant from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2019-02)。
文摘Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.
文摘During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the analysis of the metal liquid film formation at the armature/rail contact interface.1D and 3D models are developed based on the characteristic relational equation obtained from the melt liquid film model.These models incorporate thermodynamic equilibrium phase diagram,transient heat and mass transfer model,copper-aluminum alloy reaction model,nonlinear electrical conductivity relational equation and nonlinear thermal conductivity relational equation to analyze the temperature distribution and copper-aluminum intermetallic compounds(Cu-Al IMCs)formation in the melt liquid film.The wear mechanism and influence law of armature are explained in detail from different perspectives to un-derstand and predict the transition and gouging phenomena at the contact interface.The model's validity is confirmed by the results of electromagnetic launch experiments,providing insights for future structure design and material selection of the armature and rail.
基金the National Natural Science Foundation of China(Nos.51904359,51978677 and 52111530089)the Guangdong Provincial Department of Science and Technology(No.2019ZT08G090)+2 种基金the Enhanced National Key Basic Research Program(No.2019-JCJQ-ZD-352-00-04)the Science and Technology Program for Sustainable Development of Shenzhen(No.KCXFZ202002011008532)the Open Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,CUMT(No.SKLCRSM20KF002).
文摘This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdeveloped dynamic shear apparatus,and the effects of normal load oscillation amplitude,normal load oscillation period and sliding velocity were studied.The test results reveal that the shear response can be divided into three stages over a whole loading-unloading process,characterized by different time spans and stress variations.Generally,a smaller oscillation amplitude,a longer oscillation period and a fast shear velocity promote the stability of the friction system,which is also confirmed by the Coulomb failure criterion calculated based on the observed periodic apparent friction coefficient.The dynamic strengthening/weakening phenomenon is dependent on the oscillation amplitude and product of sliding velocity and oscillation period(vT).Also,the rate and state friction law incorporating the parameter a that characterizes the normal stress variation is employed to describe the dynamic friction coefficient but exhibits an incompetent performance when handling intensive variation in normal stress.Finally,the potential seismicity induced by oscillating normal stress based on the observed stress drop is analyzed.This work helps us understand the sliding process and stability evolution of natural faults,and its benefits for relative hazard mitigation.
基金supported by the National Natural Science Foundation of China (Nos. 41672268 and 41772286)the Petro China Innovation Foundation (2018D-5007-0202)the US Department of Energy (DEFE0023354)
文摘This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of mineralogy on gouge dilation and frictional strength,stability,and healing.Specifically,velocity-stepping and slide-hold-slide experiments were performed in a double direct shear configuration to analyze frictional constitutive parameters at room temperature,under normal stresses of 10,20,and 40 MPa.Gouge dilation was measured based on the applied step-wise changes in shear velocity.The frictional response of the quartz–smectite mixtures and powdered natural rocks are affected by their phyllosilicate content.Frictional strength and healing rates decrease with increasing phyllosilicate content,and at 20 wt.%a transition from velocity-weakening to velocity-strengthening behavior was noted.For both suites of gouges,dilation is positively correlated with frictional strength and healing rates,and negatively correlated with frictional stability.Changes in the permeability of gouge-filled faults were estimated from changes in mean porosity,indexed through measured magnitudes of gouge dilation.This combined analysis implies that the reactivation of caprock faults filled with phyllosilicaterich gouges may have a strong influence on permeability evolution in caprock faults.
基金funded by National Natural Science Foundation of China(Grant Nos.51509154 and 42077247)Natural Science Foundation of Zhejiang Province(Grant No.LGJ20E090001).
文摘The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus that allows direct shear of samples under coupled hydro-mechanical conditions.Velocitystepping(VS)and slide-hold-slide(SHS)experiments are performed on both bare and gouge-bearing surfaces of Xiashan basalt subjected to cyclic shear velocities at 1e30 mm/s,effective normal stresses of 1e5 MPa,and pore pressures of 70e300 kPa.The measured basalt friction coefficients are in the range of 0.67e0.74,which is sensitive to gouge thickness,normal stress,and water.Specifically,a reduction in friction coefficient is observed with an increment in gouge thickness,normal stress,and pore pressure.Based on the microscopic observation of the pre-and post-shearing sliding surfaces,this weakening effect in friction coefficient can be attributed to powder lubrication.Furthermore,the VS test results reveal predominantly velocity-strengthening behavior at investigated slip velocities,and this velocity strengthening behavior does not appear to be influenced by variations in normal stress,gouge thickness,and water.However,changes in sliding velocity and normal stress can lead to a shift between stable and unstable sliding.Specifically,stable sliding is favored by high sliding velocities and low normal stress applied in this study.Finally,we analyze the experimental data by calculating the rate-and-state parameters using the rate-and state-dependent friction(RSF)theory.Importantly,the calculated friction rate parameter(a-b)supports the velocity-strengthening behavior.Both frictional relaxation(Dmc)during hold periods and frictional healing(Dm)upon re-shearing are linearly proportional to the logarithmic hold time,which may be attributed to the growth in true contact area with hold time.This study sheds light on the roles of sliding velocity,and gouge thickness in controlling frictional strength and stability of basalt fractures.
基金supported by Postdoctoral Fellowship Program funded by the Ministry of Education of the Republic of Korea through the Chungbuk National University in 2020。
文摘Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than those of soils or rocks due to its high heterogeneity and low strength.Therefore,to improve the accuracy of analysis results,we conducted simple regression analysis and structural equation model analysis and selected major influential factors of friction characteristics among many factors,and then we deduced advanced regression model with the highest coefficient of determination(R^(2)) via multiple regression analysis.Whereas most coefficients of determination in simple regression analysis are below0.3-0.4,coefficient of determination in multiple regression analysis is remarkably large as 0.657.
文摘Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and further induce rupture propagation and earthquakes.In this study,we carried out a laboratory experiment to investigate the fluid-induced slip behavior of fault filled with gouge.The friction evolution characteristic associated with fluid pressure and effective stress was investigated during the slip process.In addition,the role transformation process of the gouge on the slip behavior of fault was revealed.The experimental result indicates that the friction on the filled fault surface is significantly affected by fault gouge.The rupture of the gouge promotes fault slip and the fluid pressure plays a vital role in the initiation of fault slip.The fault gouge enhances the shearing strength of the fault and acts as a barrier before the initial slip under fluid injection.Nevertheless,the fault gouge would accelerate the fault slip and transform into lubricant after the initial slip.
基金granted by Geological Survey Project(Grant No.1212011120072)the Project of the National Key Technology R&D Program(Grant No.2011BAK12B09)the Project of the National Natural Science Foundation of China(Grant No.41072269)
文摘Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.
基金financed by the National Youth Sciences Foundation of China (No. 41502044)
文摘The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new insights into the ongoing debate about the frictional strength of brittle fault(Haines and van der Pluijm,2012).However,neither the conditions nor the processes which
基金funded by the National Natural Science Foundation of China(Nos.42072240 and 41602218)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(No.GML2019ZD0201)the Fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Chinese Academy of Geological Sciences(Nos.J1901-30 and J1908)。
文摘K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite polytypes are critical to acquiring K-Ar isotope data for authigenic clays.In this respect,we compared the commonly used clay size separation method through centrifugation with vacuum filtration technology,showing that the former is prone to extract fractions with finer particle sizes under similar conditions,thus improving the error in the authigenic end-member age.Additionally,we demonstrated that the side-packed mounting method for X-ray diffraction analysis can significantly enhance the randomness in powder samples,thus improving the quantification accuracy compared with the front-packed and back-packed methods.The validity of our quantification method was confirmed by comparing Profex■modeling patterns with a suite of synthetic mixtures of known compositions,yielding an average analytical error of 3%.Dating results of these artificial mixtures and the reference materials indicated that a large range in percentages of detrital illite and a sufficient amount of age data will produce reliable results for ages of both extrapolated end-members.However,if the range is limited,the extrapolated age close to those of datasets is still reliable.
文摘A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the special result of fault motion while extruding or grinding. Based on the field investigation, collected from Bailongjiang fault system of Western Qinling Orogenic (QO) Belt, 44 samples of fault gouge were for quartz micro-morphology observation and statistics by the field emission SEM, and 14 samples were tested by thermo-luminescence dating. The results showed that most of the micro-morphology of quartz grains are fish scale and orange-haut fractures, but a small amount of moss-like, stalactitic, and subconchoidal fractures. Also very few decay of quartz grains and typical conchoids fracture quartz grains can be seen. This implied that the Bailongjiang fault system was motioned repeatedly in Quaternary period but main motion period was Pleistocene. 14 thermo-luminescence dating values showed herewith two groups as 343.29-184.06 ka and 92.18-13.87 ka. Therefore, the conclusions can be reached that the fault system were motioned starting at Pliocene epoch, frequently in the middle of Pleistocene (343.29-184.06 ka), and peak frequency in late Pleistocene (92.18-13.87 ka). The fault system motions have stopped at Holocene. The results are significant for the natural disaster risk evaluation in western QO region.
