Abstract:Dense non-aqueous phase liquids(DNAPLs)have characteristics such as low solubility,high volatility,and high toxicity,making their remediation particularly challenging.Accurately determining the extent of DNAPLs contamination is a prerequisite for designing an effective remediation plan.The non-invasive induced polarization(IP)method has great potential for application in site characterization of contaminated areas.However,there are many factors affecting the changes in the induced polarization signals of DNAPLs,and obtaining electrical signals through laboratory measurements is often time-consuming,labor-intensive,and subject to significant noise,making it challenging to precisely delineate and characterize the contaminated areas.This study systematically investigates the electrical signal response patterns of DNAPLs-contaminated soils through controlled laboratory batch experi-ments,and proposes a numerical simulation approach to study the electrical signal response of DNAPLs-contaminated sand columns. The results show that electrolyte conductivity and water saturation both have a negative correlation with phase,while showing a positive correlation with conductivity.This is because an increase in electrolyte conductivity directly leads to an increase in pore water conductivity,which compresses the thickness of the electrical double layer,de-creases ion mobility,and reduces polarization intensity.The increase in water saturation enhances the connectivity of pore water in the porous medium,improving conductivity and providing a continuous path for ion migration,thus hindering charge polarization.Both phase and conductivity values increase with the increase in silt content,where cation exchange enhances surface conductivity and polarization effects. Based on COMSOL Multiphysics and MATLAB platforms,a complex conductivity model for unsaturated porous media is proposed,and a series of pore network complex conductivity simulations are conducted to verify and extend the experimental results.The proposed complex conductivity model enables the acquisition of electrical signals from a numerical simulation perspective,and the simulation results under different electrolyte concentra-tions,water saturations,and soil types are generally consistent with experimental trends.It also addresses the draw-backs of laboratory measurements,such as high noise and long measurement times,and the computed results show better data comparability.This study conducts a multidimensional investigation into DNAPLs contamination through a combination of laboratory measurements and numerical simulations.The results not only provide theoretical and methodological support for the detailed characterization of DNAPLs'existence forms,migration pathways,and spatial distribution characteristics in porous media,but also have significant scientific value and practical engineering guidance for the development of an integrated technology system for DNAPLs contamination site identification,monitoring,and remediation based on non-invasive techniques.

Abstract:Nitrate pollution has received high attention due to its characteristics such as universality and the high carcinogenicity rate of its reduction products.The permeable reactive barrier(PRB),as an efficient and low-energy-consuming remediation technology,has great application prospects in the remediation of nitrate pollution.Among the commonly used wall remediation materials,zero-valent iron(ZVI)and activated carbon(AC)materials have great potential for the remediation of nitrate.However,currently,there is a lack of research on the long-term operational stability of the PRB technology,and the monitoring methods are limited.The induced polarization method,due to its greater sensitivity to the changes in the microscopic scale properties of porous media,is more helpful in characterizing the characteristics of the PRB filling medium.Therefore,it is urgent to explore the PRB operation performance monitoring technology based on the induced polarization method.This study focuses on the reaction mechanism of ZVI-AC for remediating nitrate pollution,as well as the feasibility of using the SIP techno-logy to monitor the remediation process of nitrate pollutants by ZVI-AC materials.The spectral induced polariza-tion method(SIP)in the frequency domain is used to monitor the process of remediating nitrate pollution by the composite material of zero-valent iron and activated carbon,and the remediation effect is comprehensively ana-lyzed in combination with means such as hydrochemistry,scanning electron microscopy(SEM),and X-ray photo-electron spectroscopy(XPS).The results show that:(1)ZVI-AC can give full play to the synergistic effect of the composite material.By adsorbing the oxidation products of ZVI with AC,the adhesion of these products on the sur-face of iron particles is reduced,thereby extending the service life of ZVI.(2)The polarizability can continuously decrease within the range of 0.6 to 0.7 along with the decrease in the nitrate removal rate,while the normalized re-laxation time is positively correlated with the remaining nitrate removal rate and the volume of iron particles,show-ing a strong indicative effect.The experimental results provide an important theoretical basis for the induced pola-rization method to serve as a technical means for providing low-impact and long-term monitoring for PRB in engi-neering practice.

Abstract:Groundwater,as a globally strategic freshwater resource,plays a critical role in ecosystem stability,targeted pollution remediation,and geothermal energy development.Its migration mechanisms directly influence decision-making in these major engineering fields.However,natural porous media—such as aquifer sands,gravels,and fractured rock formations—generally exhibit heterogeneous topological structures and pronounced multiscale effects,resulting in complex nonlinear behaviors in subsurface multiphase flow.Traditional hydrological observa-tion methods are limited by spatial resolution and thus struggle to reveal flow mechanisms and interaction pro-cesses at the pore scale. To overcome these limitations,this study develops a non-invasive,in situ visualization experimental platform integrating high-resolution computed tomography(CT)scanning and microfluidic chip technology,achieving mi-cron-scale spatial resolution for dynamic observation and quantitative characterization of multiphase flow in por-ous media.The experimental system systematically measures fluid saturation distribution,interface morphology evolution,and capillary pressure changes within pore structures. The results indicate that:(1)Wettability,as a key parameter controlling multiphase flow behavior,exerts regu-latory effects throughout the entire process—from pore-scale fluid distribution and interface morphology evolution to core-scale flow responses.By adjusting wettability,the spatial migration pathways and interfacial mechanical states of fluids in sandy porous media are significantly altered,triggering interface structure reconstruction and con-nectivity changes.These microscale processes directly impact displacement efficiency and residual fluid distribu-tion patterns,ultimately leading to pronounced differences in relative permeability response characteristics.(2)Un-der varying wettability,viscosity ratio,and flow rate conditions,multiphase flow exhibits diverse flow regimes and energy conversion characteristics.Wettability,flow velocity,and viscosity synergistically regulate interface stability and the power-energy transfer pathways;notably,in the critical transition zone from capillary-dominated to viscous-dominated flow,external work input markedly increases and interfacial energy fluctuates sharply. Additionally,this work assesses the advantages and technical challenges of the combined CT-microfluidic technique in multiphase flow studies.The findings provide key microscopic mechanistic support for engineering is-sues such as groundwater pollution remediation and enhanced multiphase flow efficiency,demonstrating broad ap-plication potential of non-invasive high-resolution experimental methods in environmental and energy engineering.

Abstract:Ghosts are a newly discovered category of transient luminescence events(TLEs)occurring in the middle and upper atmospheres above energetic thunderstorms.Due to the high requirements of optical shooting,the observation data that can be investigated are very scarce and are all obtained from the ground-based observations at single station.Based on the ground-based observation of seven ghost events with original optical data,in this paper we present a methodology to estimate the altitude of ghosts from single-station observation in conjunction with star-field background,and determine the altitude range of five ghosts(two of which are at the same place and time)to be 90 to 100 km.So far,ghost events are known to be accompanied by two different types of TLEs,namely"red sprite"or"gigantic jet".The accompanying relationship between ghost events and these two TLEs phenomena shows that the occurrence of ghost events may be closely related to the altitude and the strong electric field and en-ergy release during the thunderstorm.This paper further examined the atmospheric background conditions(i.e.,neutral particle density,ion concentration and electron density,etc.)upon the observations of the aforementioned seven ghost events.The density profile of neutral particles(O,N2,O2),ion(O2+and NO+)and electron density were obtained by means of the MSIS-E-90 model and the IRI model.It was found that the mutation of N2,O2 and elec-tron density played a key role in the occurrence of ghosts.These mutations of density may provide necessary medi-um conditions for the occurrence of ghosts.In this paper,by calculating the diffusivity of ghosts,it is found that the diffusivity of ghost is much lower than that of streamer discharge,which confirms that ghost emission is a form of glow discharge.Finally,the characteristics of the parent thunderstorms of ghosts are analyzed,and it is found that ghosts occur in the phase of weakening convective activity,which implies that the formation of ghost might re-quire the existence of lightning flashes with relatively high energy release.In the weakening stage of thunderstorm activity,although the convective activity decreases,the electric field of the thunderstorm cloud top may still be strong,thus providing the necessary energy conditions for the occurrence of ghost events.

Abstract:Shallow fault creep is a relatively rare phenomenon,often indicating a lower seismic risk(less strain accumulation).Previous studies have revealed shallow creep on the Gozha Co Fault in the western Qinghai-Xizang Plateau using Sentinel-1 and ALOS-2 data,but its formation mechanism remains unclear.Considering the 2008 MS7.3 Yutian earthquake that occurred to its north,which may have influenced the fault's movement,we used time series interferometry to process descending ENVISAT-1 SAR data from 2003 to 2010.This allowed us to obtain the line-of-sight deformation field before and after the 2008 Yutian earthquake.The results show that the Gozha Co Fault did not exhibit significant differential motion before the 2008 Yutian earthquake,while the fault moved left-laterally after the event.Therefore,we propose that the shallow creep on the Gozha Co Fault may have been triggered by the 2008 MS7.3 Yutian earthquake.This work is helpful for analyzing the physical mechanisms of fault shallow creep and earthquake potential in the western Qinghai-Xizang Plateau.

Abstract:The complexity of the seismicity pattern for the subduction zone along the oceanic plate triggered the outer rise events and revealed cyclic tectonic deformation conditions along the plate subduction zones.The out-er rise earthquakes have been observed along the Sunda arc,following the estimated rupture area of the 2005 MW8.6 Nias earthquakes.Here,we used kinematic waveform inversion(KIWI)to obtain the source parameters of the 14 May 2021 MW6.6 event off the west coast of northern Sumatra and to define the fault plane that triggered this outer rise event.The KIWI algorithm allows two types of seismic source to be configured:the moment tensor model to describe the type of shear with six moment tensor components and the Eikonal model for the rupture of pure double-couple sources.This method was chosen for its flexibility to be applied for different sources of seismi-city and also for the automated full-moment tensor solution with real-time monitoring.We used full waveform traces from 8 broadband seismic stations within 1000 km epicentral distances sourced from the Incorporated Re-search Institutions for Seismology(IRIS-IDA)and Geofon GFZ seismic record databases.The initial origin time and hypocenter values are obtained from the IRIS-IDA.The synthetic seismograms used in the inversion process are based on the existing regional green function database model and were accessed from the KIWI Tools Green's Function Database.The obtained scalar seismic moment value is 1.18×1019 N·m,equivalent to a moment mag-nitude MW6.6.The source parameters are 140°,44°,and-99°for the strike,dip,and rake values at a centroid depth of 10.2 km,indicating that this event is a normal fault earthquake that occurred in the outer rise area.The outer rise events with normal faults typically occur at the shallow part of the plate,with nodal-plane dips predominantly in the range of 30°-60° on the weak oceanic lithosphere due to hydrothermal alteration.The stress regime around the plate subduction zone varies both temporally and spatially due to the cyclic influences of megathrust earthquakes.Tensional outer rise earthquakes tend to occur after the megathrust events.The relative timing of these events is not known due to the viscous relaxation of the down going slab and poroelastic response in the trench slope region.The occurrence of the 14 May 2021 earthquake shows the seismicity in the outer rise region in the strongly coupled Sunda arc subduction zone due to elastic bending stress within the duration of the seismic cycle.

Abstract:Interchange instability is widespread in both engineering applications and natural environments and is recognized as one of the primary mechanisms for radial mass transport within Jupiter's magnetodisk.In this study,the dispersion relation and the instability criteria of the interchange instability in Jupiter's inner magneto-sphere are derived by considering the parameters of Jupiter's inner magnetosphere(Feng et al.,2025)and applying the ideal magnetohydrodynamic(MHD)theory without assuming the local approximation(i.e.,the perturbation wavelength is much smaller than the characteristic scale length).The mode number and growth rate of the domin-ant mode are obtained through theoretical analysis.Under the current parameters of Jupiter's inner magnetosphere,the interchange mode is found to be stable within the Io plasma torus,whereas unstable regions exist outside the torus.The unstable occurrence regions are given by the theoretical model.It is also found that the centrifugal force and density gradient outside the Io plasma torus jointly drive the interchange instability,while the curvature of the dipole magnetic field and entropy gradient exhibit stabilizing effects on the interchange mode.The growth rate of instability increases with the azimuthal mode number for values below 10,beyond which it saturates.Additionally,the growth rate decreases with increasing radial mode number.Compared to theoretical results from Newcomb(1961)and Ferrière et al.(1999),our theoretical model predicts instability regions almost identical to those of Ferrière's theoretical model,but differs from Newcomb's theoretical model,which suggests that the entire region outside the Io torus is unstable.This difference mainly arises because Newcomb's theoretical model adopts a slab geometry,which neglects the stabilizing effect of the curved magnetic field.It also shows that the growth rate of the dominant interchange mode in our theoretical model is close to that of Ferrière's theoretical model,indicating that the local approximation is suitable for describing the interchange instability of Jupiter's inner magnetosphere.However,the growth rate of the dominant mode in our theoretical model is approximately one order of magnitude higher than that of the numerical result.

Abstract:Near space refers to the complex transition region between the Earth's atmosphere and space,with its height between 20-100 km,including the stratosphere,the mesosphere and the lower thermosphere which are important components of the Earth's atmospheric system.The near space is affected not only by small-scale disturb-ances in the troposphere but also by planetary waves in the middle and upper atmosphere.There are also atmo-spheric dynamic processes in the region and physical and chemical interactions between layers of the atmosphere,which make the study of near space difficult.Scholars at home and abroad have done a lot of research on the ap-plication of machine learning and deep learning algorithms in the field of space physics,and achieved good results.However,due to the complexity and variability of atmospheric environment,there is little research on using deep learning algorithm to forecast environmental temperature in near space.The study of temperature forecasting in near space is of great scientific significance for understanding atmospheric dynamics,cross-layer coupling and ana-lyzing atmospheric fluctuations.In this paper,CNN-LSTM algorithm is used to forecast temperature in near space based on MERRA-2 datasets.The CNN part can effectively extract spatial features and the LSTM part can capture temporal dependencies.Its output window is 7 days,and the relative error is controlled within 2%compared with the original data.On this basis,we do some research on the sensitivity of the algorithm in season,altitude and lati-tude.The results show that in summer and autumn of the Northern Hemisphere,the forecast results are better,and the accuracy of the forecast model is more reliable at low latitudes.

Abstract:The static and dynamic stress changes induced by earthquakes can further trigger seismic events on surrounding or even remote faults.This phenomenon,known as static and dynamic triggering of earthquakes,has significant implications for earthquake prediction and seismic hazard assessment.Consequently,it has remained a focal point of seismological research over the past three decades.However,key challenges persist in effectively dis-tinguishing the relative contributions of static and dynamic triggering mechanisms in near-field seismic triggering,as well as in explaining the phenomenon of delayed dynamic triggering.In this study,we synthesize the main find-ings from prior research in the field and present the following conclusions:①Static triggering is the dominant mechanism in near-field earthquake activation,while dynamic triggering serves as a supplementary mechanism un-der certain favorable conditions.When specific thresholds are met,dynamic stress changes can participate in near-field triggering.②The Coulomb failure model and rate-and-state(R-S)friction law can be employed to simulate the advance of earthquake nucleation timing caused by static stress changes.The results exhibit both first-order agreement and second-order discrepancies,reflecting model-dependent nuances.③The delayed nature of dynamic triggering cannot be adequately explained by conventional Coulomb failure models or the R-S law.Instead,such phenomena must be interpreted through different physical processes—such as fluid-related mechanisms—depend-ing on the geological context of the fault zone.Nevertheless,the eventual occurrence of seismic events often still necessitates the contribution of static stress perturbations.④Both theoretical modeling and laboratory experiments highlight the limitations of dynamic triggering.Observed dynamic triggering phenomena are generally contingent upon two key factors:sufficiently large amplitudes of dynamic stress changes and fault conditions approaching the critical state of failure(e.g.,low effective normal stress or proximity to tectonic loading thresholds).The degree to which a fault nears failure and the regional tectonic environment(such as the presence of sedimentary layers)jointly determine the threshold required for dynamic triggering in a given area.Additionally,while seismic wave frequency is known to influence triggering potential,its relationship with dynamic triggering thresholds remains complex and contentious.⑤Additionally,this paper discusses phenomena such as fluid injection-induced seismi-city,solid Earth tide-triggered earthquakes,and the triggering of slow slip events.It is argued that the triggering mechanisms of these phenomena are generally consistent with the above conclusions.

Abstract:Large igneous provinces(LIPs)play an important role in crustal growth,metallogenesis of metal elements,global climate changes and life evolution.Despite extensive studies of near-surface geological records of LIPs,our knowledge about the middle-lower crustal intrusions of LIPs is very limited.By comparing geological and geophysical data from the Emeishan LIP,the Siberian Traps,and the Central Atlantic Magmatic Province,we investigate the effects of the magmatic plumbing system of LIPs on the continental crustal structure and global cli-mate.Due to differences in the stress regime,the lithospheric thickness,and plume-lithosphere interaction,each LIP may contain a unique plumbing system and crustal structure,which will affect the dynamic evolution of the continental lithosphere.Thermal-mechanical erosion of the lithosphere by a mantle plume will cause lithospheric thinning.Under regional far-field extensional stress,the thermal weakening effect by eruption of LIPs along pre-ex-isting weak zones can enhance the lithospheric extension and trigger the continental break-up.By contrast,if LIPs are far away from divergent plate boundaries or under regional compression,magma underplating and crustal intru-sions will increase the crust-mantle coupling and the lithospheric strength,and consequently allow the long-term stability of cratons.Volcanism of LIPs is one of the controlling factors of global climate change,meanwhile large amounts of CO2 and methane released by contact metamorphism between intrusions and surrounding rocks also contribute to climate changes.The plumbing system of LIPs establishes a bridge between deep mantle processes and the Earth's surface system.Recognition and modeling of the plumbing system of LIPs will provide new in-sights into the plume-lithosphere interaction,metallogenic mechanisms of LIPs,as well as the relationships between LIPs,the global climate change and massive extinction events.

Abstract:The"23.7"heavy rainfall event in Beijing triggered multiple geological disasters of flush flood and debris flows,resulting in 33 deaths,18 missing persons,and significant economic losses,which has drawn wide-spread social attention.Currently,geological disaster monitoring and early warning systems struggle to achieve pre-cise warning in complex environments,making the development of refined monitoring and early warning technolo-gies a hot and challenging topic in the research of mountain disaster and engineering disaster prevention and con-trol.Through field investigations and the analysis of continuous records from nearby seismic stations,this study de-termined that the debris flow at Che'erying Village at the foot of the Western Hills in Beijing occurred at 03:36 on July 31,2023(UTC+0,time),with the flood peak height of approximately 3.5 m.The seismic records triggered by this disaster event exhibited a spindle shape,lasting for about 100 minutes.This study employed three methods—the long-term and short-term window ratio,the statistical Benford's Law,and frequency-based feature detection,to identify the waveform of the Che'erying flash flood and debris flow event recorded at the LQS station.The results indicate that the traditional long-term and short-term window ratio method struggled to establish an ef-fective threshold to distinguish between background noise and the prolonged process of the flash flood and debris flow,failing to identify this event.The identification method based on Benford's Law could not detect the disaster event without a noise threshold;however,when a statistical threshold based on background noise was set,it suc-cessfully detected and identified the disaster event.The centroid frequency-based detection method,requiring no prior information,effectively utilizes the rich time-frequency amplitude variations of high-energy events to accur-ately identify the small-scale flash flood and debris flow event at a distance of 1.5 kilometers.This method en-hances the efficiency of geological disaster identification and detection based on seismic signals and holds promise for providing more effective technology,particularly with the dense seismic network in the Beijing area in the fu-ture.

Abstract:At Beijing time 19:58 on April 9,2000,a large landslide occurred in Yigong area,Bomi County,Linzhi City,southeastern Qinghai-Xizang Plateau,caused extensive damage to about 8 km2 of forest,blocked the river and formed the Yigong lake.Seismic waves can remotely detect the occurrence process of landslide events,which helps to quantitatively analyze their dynamic parameters of different sliding stages.Because of the large size and strong energy of the event,the seismic waveform of the Yigong landslide can be clearly seen on the remote seismic stations.We analyzed the dynamic process of the 2000 Yigong landslide using broadband seismic wave-forms of the China Earthquake Networks Center,and found that the event lasted about 215 s,including the pre-slip initialization(about 65 s),the main slip(about 90 s),and the post-slip adjustment(about 60 s)phases.The duration of the initialization phase is relatively long and the low-frequency signal is weak.However the high-frequency sig-nal gradually increased,indicating that the landslide is started with broken collapse.The main sliding phase is fur-ther divided into accelerated and decelerated sliding stages.During the accelerated sliding stage,the amplitudes of both the high-frequency and low-frequency signals are large.The terrain slope is steep and the material accelerated to slide in the Zhamunong valley.About 35 s after the acceleration process,the maximum speed reached about 191 m/s and the horizontal displacement of the landslide movement is about 3.1 km.By comparison,during the de-celeration sliding stage,both the high-frequency and low-frequency signals decreased.This observation is corres-ponding to the widening of the landslide bed and the slowing of the slope.Then the speed of landslide movement continuously decreased to zero.The maximum horizontal and vertical displacements reached about 6.0 km and 3.2 km after 90 s,respectively.In the post-sliding adjustment stage,the amplitude of both high-frequency and low-frequency signals gradually weakens,which mainly reflects the scattered deposition of landslide materials at the bottom of the Zhamunong valley.The volume and sliding speed of the 2000 Yigong landslide is obviously larger than other landslides that have recently occurred in the southeastern Qinghai-Xizang Plateau.These observations suggest that the sliding friction of sediments in the valley decreased due to melting water and precipitation in the source area and giant deposits are formed.It is the major reason for the blockage of the Yigong Zangbu river and the formation of the Yigong Lake.

Abstract:In airborne transient electromagnetic(ATEM)surveys,sferic significantly degrades data quality due to its randomness and uncertain energy amplitude.This study explores three methods for removing sferic:wavelet decomposition and reconstruction,α-trimmed mean filter,and Hampel filter.Their respective advantages and ap-plication scenarios in signal processing are compared.Wavelet decomposition and reconstruction offer multiscale and multiresolution signal analysis,allowing simultaneous consideration of time and frequency characteristics.The choice of basis functions affects global properties and phase shifts,while the number of decomposition levels influ-ences data smoothing,and threshold settings impact noise removal effectiveness.α-trimmed mean filtering re-moves noise by averaging the remaining data after excluding the maximum and minimum values within a window,thus demonstrating adaptability.The Hampel filter detects outliers using median and median absolute deviation(MAD),effectively targeting noise removal,particularly suitable for scenarios requiring signal detail preservation.This study enhances the Hampel filter,reducing computational overhead while ensuring accurate outlier detection.Simulation experiments on random signals and field-collected ATEM data validate the denoising capabilities of the three methods,revealing that the Hampel filter achieves optimal sferic reduction.

Abstract:The magnetotelluric(MT)method is a core technology widely used in geophysical exploration and commonly used in geological surveys,resource exploration and geodynamic research.However,MT data are sus-ceptible to complex noise,including nonlinear and non-stationary noise,which significantly reduces data quality and interpretation accuracy.Although traditional denoising methods(such as sparse representation and wavelet transform)can improve the quality of some data,they have limitations such as complex parameter adjustment and insufficient robustness when dealing with diverse noise types.In order to solve the above problems,this paper pro-poses an innovative MT data denoising method based on inverse autoencoder and channel attention mechanism.The inverse autoencoder enhances the ability to capture complex signal features through the process of dimension-ality increase and dimensionality reduction,achieving efficient signal-to-noise identification and signal fitting;the channel attention mechanism further improves denoising accuracy by dynamically adjusting the weight of feature channels.On this basis,an end-to-end deep learning framework is designed to process MT data in complex noisy environments.Experimental results show that this method exhibits superior denoising performance under a variety of noise conditions.It is significantly better than traditional methods in indicators such as correlation coefficient(CORC),normalized root mean square error(NRMSE)and signal-to-noise ratio(SNR);in addition,in the analysis of apparent resistivity-phase curve and electromagnetic field polarization direction,the method in this paper shows higher robustness and consistency.This shows that the method in this paper can effectively improve the quality and interpretability of MT data and provide reliable technical support for geophysical exploration.

Abstract:Airborne magnetotelluric method is an airborne frequency-domain electromagnetic method that measures the natural electromagnetic fields.It has the advantages of great detection depth,high measurement effi-ciency,minimal terrain influence,and being environmentally friendly.This paper briefly introduced the develop-ment history and measurement principles of airborne magnetotelluric method.Then introduced the basic concept of admittance tensor and the working methods of airborne magnetotelluric measurement using admittance tensor.Fi-nally,this method was applied to engineering surveys under complex terrain conditions.By analyzing the charac-teristics of inversion resistivity and magnetic susceptibility,effective detection of rock masses and fracture struc-tures was achieved.Application example showed that the airborne magnetotelluric method based on the admittance tensor is sensitive to geoelectric boundary and can be used for detecting near-surface and deep structures in com-plex environmental areas.

Abstract:Selecting an appropriate index is essential for the scientific and effective early warning of land-slides.To explore the potential use of geomagnetic fluctuation signals as an early warning index for landslides,this study investigates the characteristics of geomagnetic fluctuations associated with landslides.The Xinmocun land-slide is chosen as the case study.Using cross-correlation analysis,we examine the data correlation between obser-vation stations near the landslide and count the frequency of disturbance signals during the observation period to identify geomagnetic disturbance phenomena associated with the landslide.The study aims to elucidate the charac-teristics and patterns of geomagnetic disturbance signals related to landslides.The results reveal that significant geomagnetic disturbances were observed before the destabilization of the Xinmocun landslide.These disturbances predominantly occurred in the main sliding direction of the landslide and were marked by the presence of sustained high cross-correlation(CC)values(yellow,CC>0.45)in areas near the landslide point.These geomagnetic disturb-ance signals persisted for a prolonged period before and after the landslide event,displaying a pattern of frequent signals prior to instability,rapid reduction at the point of landslide failure,and strong correlation with the deforma-tion and damage characteristics of the landslide.The findings suggest that geomagnetic disturbance signals can serve as a novel indicator for landslide monitoring.This approach offers the potential to identify the location of po-tential landslides,assess the evolutionary stages of sudden landslides,and enable effective early warning.Thus,the geomagnetic disturbance signals provide a promising tool for enhancing landslide prediction and risk management strategies.

Abstract:Volatiles(such as H2O,CO2)are the crucial factors controlling the physical-chemical properties and dynamic processes of the multi-layer system within the Earth,and therein play an important role in plate tectonics,magmatic-mineral activities,and even the development of the planet's habitable environment.Because volatiles can drastically alter the physical characteristics of crust-mantle rocks,the primary method for determining their content and distribution within the Earth is to combine geophysical observations with high-temperature and high-pressure petrophysical experiments.Of the many physical properties,electrical conductivity is particularly sensitive to the presence and abundance of trace amounts of volatile materials,and therefore the deep conductivity structure de-rived from natural-source electromagnetic(EM)sounding methods such as magnetotellurics(MT)and geomagne-tic depth sounding(GDS)offers crucial observational information for constraining the distribution of volatiles in the crust and mantle.This review firstly summarizes the basic principles and characteristics of the major natural-source EM sounding methods,and presents in detail the high-temperature and high-pressure experimental studies on the electrical conductivity of major minerals/rocks and melts in the crust and mantle,then reviews typical cases combining the two methods to study the distribution of deep volatiles in different geological settings.Finally,this review synthesizes and discusses the existing shortcomings and difficulties of current research,and further pro-spects the future development directions and potential challenges.

Abstract:Geophysical electromagnetic data inversion is a typical underdetermined problem.Due to the limit-ations of observational data,individual geophysical methods often suffer from significant non-uniqueness and un-certainty,making it challenging to provide accurate and stable interpretations of subsurface geological structures.To address this issue,joint inversion techniques have emerged as a key research direction in geophysical explora-tion.By integrating the advantages of different geophysical methods,joint inversion enhances the resolution and re-liability of inversion results.In recent years,with the rapid advancement of computational technologies and novel numerical algorithms,various joint inversion approaches have been proposed and widely applied.These primarily include empirical coupling methods based on petrophysical properties,structural coupling methods utilizing spatial correlation constraints,and prior information-constrained methods based on Bayesian theory and fuzzy clustering,and so on.The core concept of these methods is to exploit the complementary information from different geophysi-cal techniques to optimize the joint inversion objective function through petrophysical relationships,spatial gradi-ent constraints,or probabilistic modeling.This reduces solution non-uniqueness and enhances the characterization of subsurface geological structures.Joint inversion techniques have demonstrated significant success in applica-tions such as mineral exploration,energy resource detection,geological mapping,and deep structural studies. Despite their promising potential,joint inversion techniques still face several challenges in practical applica-tions.These challenges include the rational construction of relationships between physical fields,the optimization of regularization strategies,the improvement of computational efficiency,and the handling of complex terrain ef-fects.Future research in joint inversion will focus on the following aspects:(1)leveraging artificial intelligence and data-driven methods to learn nonlinear mappings between petrophysical parameters from large-scale training data-sets,thereby improving inversion speed and accuracy;(2)integrating multi-source data and prior information with-in a probabilistic inversion framework to provide uncertainty quantification and enhance the reliability of inversion results;(3)employing multi-resolution optimization strategies,wherein a coarse-scale inversion captures the over-all structure before progressively refining the model to improve computational efficiency and mitigate local mini-ma issues;and(4)integrating seismic,gravity,magnetic,and electromagnetic data to enhance inversion robustness,while incorporating real-time monitoring data to better capture subsurface dynamic processes. With advancements in high-performance computing,artificial intelligence,and novel geophysical observation technologies,joint inversion methods are expected to play an increasingly crucial role in resource exploration,sub-surface structure detection,and geological hazard monitoring,providing higher-resolution and more accurate sub-surface imaging techniques for Earth science research.

Abstract:Marine controlled-source electromagnetic method(MCSEM)is an important technique in seabed resource exploration.This method overcomes the shortcomings of natural field electromagnetic methods,such as weak signals and insufficient high-frequency information,and offers advantages such as wide detection range,high efficiency,and low cost.Therefore,it shows great potential in seabed resource and energy exploration.This paper first provides a brief review of the working principle and technological development of the MCSEM method,then focuses on the latest research trends in three-dimensional forward and inversion numerical simulation,elaborates on the forward and inversion methods of MCSEM,among them,geologically-guided or seismically-results-guided marine electromagnetic inversion or joint inversion can reduce the inversion multiplicity and be more advantage-ous than a single inversion observation data in geological interpretation.and presents application examples of the method in seabed oil,natural gas hydrates,and polymetallic mineral exploration.Based on the current state of re-search,this paper proposes key directions for the future development of MCSEM:improving the computational precision and efficiency of algorithms,conducting in-depth studies on three-dimensional anisotropic forward and inverse models,and enhancing data processing techniques.These strategic suggestions aim to promote the continu-ous advancement of marine electromagnetic technology and provide theoretical support and practical guidance for precise seabed resource exploration.

Abstract:To elucidate the contact relationship between Indian and Eurasian plates along the Yarlung-Zangbo suture zone(IYS)and associated geodynamic processes,we acquired a high-resolution magnetotelluric(MT)pro-file extending 20 km across the Motuo fault zone near Beibeng Township,Motuo County,eastern Xizang.This NW-SE oriented transect employed 30 MT stations with approximately 300-m spacing,covering frequency bands of 10000-0.0001 Hz to resolve crustal structure down to 30 km depth.Key findings from the electrical resistivity model reveal:(1)At shallow crustal levels(<5 km depth),the Motuo fault system exhibits a negative flower struc-ture characterized by downward-converging conductive shear zones,diagnostic of dominant strike-slip deforma-tion.(2)Preservation of Indian slab subduction traces beneath the Lhasa Block along the IYS,with possible deve-lopment of a pop-up structure in the Indian upper crust near the eastern Himalayan syntaxis.(3)The resistive Lhasa Terrane upper crust is～20 km thick-33％thinner than the 30-km average in southern Xizang.This disparity im-plies either:(ⅰ)incomplete syn-collisional crustal shortening due to strain partitioning into strike-slip faults,or(ⅱ)absence of crustal growth episodes that thickened the Lhasa Terrane.(4)A mid-crustal conductor at 15-30 km depth aligns with the suture zone.Its upward-flaring geometry indicates southward migration of melts from the Lhasa lower crust,which is facilitated by transpressional uplift along the IYS.These results demonstrate that the Motuo fault system operates as a crustal-scale transfer zone,where strike-slip kinematics preserve early collisional features while enabling melt migration through reactivated suture structures.The integrated model provides new constraints on strain accommodation mechanisms during continental indentation.