Search Results (592)

Northeast China, situated in the eastern Central Asian Orogenic Belt (CAOB), marks the terminal closure zone of the Paleo-Asian Ocean (PAO) (eastern segment). At present, due to extensive Quaternary cover, the structural deformation characteristics and deep structure of the Solonker Suture Zone in the east of the Nenjiang–Balihan fault remain poorly constrained, which limits our understanding of the tectonic evolution of the PAO. This study integrates deep seismic reflection (DSR) and magnetotelluric (MT) sounding profiles to investigate the crustal structural, sedimentary framework, and tectonic evolution of the oceanic and continental crusts along the western slope of the Songliao Basin. Two regional detachment surfaces (D1 and D2) were identified. The D2 interface demarcates the upper crust’s basal boundary, overlain by multiple high-amplitude monoclinic reflections. The area below the D2 interface exhibits a network structure of arcuate and variably oriented reflections, indicating a dual-layered orogenic structure. The upper crust exhibits distinct structural domains defined by strongly contrasting monoclinal reflections: north-dipping, low-resistivity zones in the southern sector and south-dipping, high-resistivity zones in the northern sector. These oppositely oriented reflections have been interpreted as marking an Early Paleozoic accretionary wedge and oceanic island arc, respectively. Interposed between these opposing structural domains, the Paleozoic to Early Mesozoic forearc basin sequences are preserved, with a pre-Middle Permian oceanic basin identified north of the study area. By integrating characteristics of seismic reflection sequences with regional geological data, this paper clarifies the processes of closure and collision at the northern margin of the PAO (Eastern Segment). Full article

Earthquakes are rare and infrequent natural phenomena with considerable consequences for the urban environment, human life and society. Croatia is a country highly exposed to seismic risks due to its geographical location and its large stock of unreinforced masonry buildings (URM). This article proposes an assessment of their vulnerability by combining a macroseismic approach, allowing for a comprehensive analysis of a group of buildings, with detailed numerical modelling of a building in Zagreb using 3Muri 12.2 software. Three reinforcement techniques are compared in terms of their structural performance, cost, carbon footprint and compatibility with the built heritage. The study shows that each method has advantages and limitations: shotcrete is low-cost but has a high carbon impact and can be too invasive for heritage buildings; FRP offers the best structural performance but remains very expensive, while FRCM appears to be a balanced compromise, combining performance, durability and compliance with architectural conservation constraints. This article highlights the importance of adapting the approach to each situation and combining reliable assessment with appropriate reinforcement solutions. It also invites reflection on the possibility of linking seismic interventions and energy renovations to improve safety, economy, sustainability and living comfort. Full article

Fluid seepages and seabed pockmarks are widely observed on continental margins worldwide in hydrate- and non-hydrate-bearing sediment. Subsurface gas chimneys connecting seafloor pockmarks to underlying gas reservoirs are commonly revealed by seismic reflection data, indicating pathways of past and present fluid migration. Fluid seepage occurs when the seal of a gas reservoir is breached, allowing fluids to migrate upward and vent at the seafloor, forming pockmarks. In hydrate-bearing settings, gas reservoirs beneath hydrate layers typically consist of coexisting water and gas phases. However, quantitative constraints on gas saturation in free-gas zones beneath hydrates inferred from pockmark morphology remain limited. In this study, a two-phase pockmark model was developed to investigate gas-chimney growth and pockmark formation, and to estimate gas saturation in free-gas zones below hydrates using pockmark depth and gas-zone thickness as key parameters. The model was applied to the Storegga Slide region off Norway, where hydrates, pockmarks, and chimney-like seismic anomalies have been documented. Here, the application is intended to represent localized near-threshold (pre-seepage) conditions leading to pockmark initiation, rather than the present-day post-venting state. Model results for the initiation (near-threshold, pre-venting) stage indicate that the effective gas saturation in the free-gas reservoir beneath the hydrates was approximately 1.36–1.58% for gas-zone thicknesses of 50–100 m, and that the corresponding chimney-propagation timescale during initiation was on the order of ~200 years. These estimates represent threshold conditions required for seal breach and pockmark formation rather than present-day seepage states. During venting, methane gas may form hydrates within the chimney inside the hydrate stability zone, while authigenic carbonates precipitate in pockmarks and shallow sediments. These secondary hydrates and carbonates eventually seal the chimney, leaving behind a residual gas chimney in the subsurface sediment. Full article

In seismic imaging, the trace mixing process involves merging neighboring traces in seismic data to enhance the signal-to-noise ratio and improve the continuity and spatial coherence of seismic data. In regions with complex subsurface structures, current trace mix filters are often ineffective as they introduce artifacts that reduce interpretability and obscure the signatures of important structures, such as faults and folds. We introduce the selective trace mix as a novel, data-dependent filter. This filter enhances amplitude consistency, spatial coherence, and the definition of reflections, while it preserves complex structures and maintains their clarity. Selective trace mix uses sequential steps of evaluation, referencing, exclusion, weighting, and normalization of all samples within the filter operator. As a result, selective trace mix is a temporally and spatially variable, data-dependent filter. The filter’s effectiveness is validated using both synthetic and real field seismic data. Synthetic data is a portion of the Marmousi seismic model, while real data include land and marine seismic datasets imaging complex subsurface fault/fold structures. When compared to three of the commonly used conventional filters, the selective trace mix yields far better results in terms of horizon integrity and fault clarity. Full article

Reliable numerical simulation of concrete-encased steel (CES) composite columns remains challenging, and practical fiber-element modeling can be sensitive to confinement representation and to discretization and integration choices. Although CES columns offer superior structural performance, accurate simulation is difficult due to the complex interaction between steel and concrete under cyclic loading. Current seismic design codes, such as ASCE/SEI 41-17, often simplify modeling parameters by underestimating composite action, which can lead to uneconomical and overly conservative assessments that do not fully reflect the confining effect of the concrete encasement and the buckling restraint of the steel core. This study proposes a practical guideline for constructing an accurate analytical model for CES columns using nonlinear fiber-element analysis, with a specific focus on material constitutive laws. To validate the proposed strategy, nonlinear analyses were conducted and compared against a comprehensive database of 79 experimental specimens compiled from previous studies. The predicted-to-test peak strength ratio shows a mean of 1.02 (standard deviation of 0.058). Sensitivity studies indicate that responses stabilize beyond ~23 fibers (<1.5% error), reducing computation time by ~40% on average (from 52 to 23 fibers) compared with dense discretization while maintaining reliable hysteretic response prediction. Full article

Monitoring the hydrochemistry of groundwater and the H-O isotopes in the Jingpo Lake volcanic area, China, is fundamental to studying the mechanisms of volcanic and seismic events, as well as the associated hazards. To study the hydrogeochemistry of fluids in the Jingpo Lake volcanic area, water samples from seven sites were tested for hydrogeochemistry, H-O isotopes, and radon (Rn) content. The genesis and evolution of the groundwater system were elucidated through an integrated approach employing Gibbs diagrams, ionic ratio analyses, reservoir temperature estimation (silica–enthalpy method), and inverse geochemical modeling with PHREEQC. The results showed that the dominant water chemistry type was HCO₃⁻, primarily influenced by volcanic rock weathering and deep hydrothermal activity. Spring and well water were influenced by cation exchange, adsorption, and rock weathering dissolution. The H-O isotope composition and radon content indicate that atmospheric precipitation is the main source of supply, while well water is influenced by deep fluids. According to the Na-K-Mg triangle diagram, most of the groundwater was shallow and immature, whereas the well water was partially balanced. The temperature of the geothermal water was controlled by the geothermal gradient, depending on its occurrence and circulation depth. Additionally, the equilibrium temperature of the thermal reservoir was calculated using the silica–enthalpy equation method, with the concentrations of dissolved components in the water taken into account. The temperature of the thermal reservoir of the well water and the depth of groundwater circulation were estimated. The original reservoir temperature in the study area was calculated to range from 108 °C to 156 °C, with a geothermal water-to-shallow groundwater mixing ratio of between 71% and 85%. The estimated shallow temperature ranged from 64.9 °C to 74.9 °C. These hydrogeochemical signatures reflect active water–rock interactions and the contribution of deep-seated geothermal fluids, providing robust evidence for ongoing geothermal activity in the Jingpo Lake volcanic system. The findings enhance our understanding of the recent geological evolution and present-day hydrothermal processes of this potentially active volcanic field, which establishes a crucial hydrogeochemical baseline for future monitoring and hazard assessment studies. Full article

During seismic exploration, seismic data is collected to determine underground structural features and hydrocarbon-bearing stratum interfaces. The seismic data inversion process is highly complex and susceptible to interference from noise, which may lead to significant errors in inversion and affect comprehensive stratigraphic interpretation. The application of machine learning to seismic data interpretation and denoising remains technically challenging and yields suboptimal results. Micromotion exploration technology employs conventional “noise” as its signal source, utilizing widely occurring regular noise. On the basis of the theory of stationary random processes, it extracts frequency curves of surface waves from micromotion signals and performs inversion to obtain underground shear wave velocity profiles. Owing to its simplicity, cost-effectiveness, and environmental friendliness, micromotion exploration has notable advantages in structural exploration and hydrocarbon discovery. The micromotion detection results of an experimental area can quickly reflect the location of fault zones. When combined with electrical logging, this method is effective for shallow gas reservoir structure detection. Full article

Damage to tunnel structures under seismic action severely affects engineering safety and post-earthquake rescue, making it crucial to enhance the seismic capacity of tunnels. Current seismic approaches for tunnel engineering mainly include seismic isolation (shock absorption layer technology), damping, and anti-seismic, among which shock absorption layer technology has attracted considerable attention due to its economic efficiency and effectiveness. However, existing research has primarily focused on single shock absorption layer materials, lacking systematic classification frameworks and multi-dimensional comparative analyses, making it difficult to provide comprehensive guidance for material selection and engineering applications. This paper systematically reviews the research status of tunnel shock absorption layers. First, it elucidates three core mechanisms through which shock absorption layers function: wave-impedance mismatch and energy reflection, material damping and energy dissipation, and system stiffness reduction with natural period elongation. This study proposes categorizing the existing materials for tunnel shock absorption layers into five main types: foam concrete, other types of concrete, polymer materials, asphalt materials, and porous metallic materials. A detailed introduction is provided for each material category, covering their physical properties, shock absorption performance, advantages and disadvantages, as well as relevant optimization studies conducted to address material limitations. By comprehensively comparing the mechanical properties, shock absorption performance, durability, constructability, recyclability, and economy of these five types of materials, revealing their unique advantages and applicable limitations in tunnel shock absorption. Finally, the limitations of existing research are summarized, development directions for tunnel shock absorption layer materials are proposed, and the future research trend of tunnel damping layer technology is envisioned. This paper provides a reference for the research, selection, and standard formulation of tunnel shock absorption layer materials. Full article

For arch dam seismic safety evaluation, the finite element equivalent stress method has been widely used, and existing studies have realized mature equivalent stress calculation along the foundation surface path. However, from the scientific research perspective, there is a lack of a full dam surface equivalent stress characterization method for arch dams under seismic action; from the engineering practice perspective, the traditional path method cannot fully reflect the overall stress distribution of the dam, leading to insufficient comprehensive safety evaluation. To accurately assess the impact of seismic action on the overall structural safety of arch dams and address the above limitations, this study develops a methodology for calculating equivalent stress across the entire dam surface of arch dams under seismic action. Taking a concrete arch dam as the research object, a seismic wave input method based on viscoelastic artificial boundaries is employed. Three-dimensional finite element analysis of the arch dam is performed using ABAQUS, integrated with Python-based secondary development to extract stress along the integration path of each arch ring layer and calculate sectional internal forces. The equivalent stress of each arch ring layer integration path is then processed using the material mechanics method to obtain the equivalent stress distribution across the entire dam surface. A comparative analysis is conducted between the equivalent stress on the entire dam surface and that along paths on the foundation surface regarding the seismic dynamic response and behavioral patterns of the dam. The results demonstrate that the full dam surface equivalent stress approach not only accurately captures the extreme tensile and compressive stress values in the downstream foundation area but also identifies stress extrema in the upstream dam crest region, thereby achieving comprehensive characterization of the dam stress field under seismic action and enhancing both the efficiency and accuracy of equivalent stress calculations for arch dams. This method provides more comprehensive and reliable data support for seismic design optimization and reinforcement of arch dams. Compared with the traditional foundation surface path method, the proposed method achieves 100% identification of the whole dam surface stress extremum areas, with a maximum relative error of only 1.62% in the overlapping calculation area. Full article

Forecasting post-seismic landslide displacement is challenged by the difficulty in distinguishing short-term acceleration from creep and the risk of spatiotemporal leakage. To address this, an interpretable deep-learning framework is developed, integrating SBAS-InSAR time series with an Attention-enhanced Gated Recurrent Unit (Attention-GRU). Prior to modeling, a multi-stage preprocessing strategy, including empirical mode decomposition, is applied to mitigate noise and delineate active deformation zones. Unlike standard architectures, the model’s temporal attention mechanism adaptively amplifies critical precursory acceleration phases. Furthermore, a strict landslide-object-based partitioning strategy is employed to rigorously mitigate spatiotemporal leakage. The framework was evaluated in the Le’an Town landslide cluster using multi-source data. Targeting identified hazardous regions, the method achieved an R² of 0.93 and reduced MAPE by 42.7% relative to the SVR baseline. This reflects a location-specific predictive capability, within active zones rather than regional generalization. SHapley Additive exPlanations (SHAP) further confirmed the model captures physical relationships, such as sensitivity to 25–35° slopes and vegetation degradation. Ultimately, the proposed framework offers a transparent, physically interpretable tool for operational hazard mitigation. Full article

This article examines the behavior of seismic noise fields over the Japanese islands recorded by the F-net seismic network for 1997–2025. This paper uses nonlinear noise statistics: the entropy of the wavelet coefficient distribution, the Donoho–Johnston (DJ) wavelet index, and the multifractal singularity spectrum support width. These parameters were chosen because their changes reflect the complication or simplification of the noise structure. Changes in the structure of seismic noise properties are analyzed in comparison with a sequence of strong earthquakes. Using a model of the intensity of interacting point processes, the effect of the leading of local noise property extrema relative to the seismic event times is estimated. Using the Hilbert–Huang decomposition, the synchronization of the amplitudes of the envelopes of noise property time series for different IMF levels is estimated. A sequence of weighted probability density maps of extreme values of noise properties is analyzed in comparison with the mega-earthquake of 11 March 2011 and the preparation of another possible strong seismic event. Full article

To address the challenge that traditional dam model materials are difficult to simultaneously meet the requirements of microstructural similarity, dynamic damage simulation, and environmental friendliness, a novel microparticle mortar simulated concrete was developed. This new material consists of cement, sand, gypsum, mineral oil, water, and baryte sand. Through systematic material mechanical tests, the effects of each component on the material’s strength, density, and elastic modulus were revealed, and the optimal mix ratio was determined. This enabled precise control of low elastic modulus and had a high density, while the material is environmentally friendly, non-toxic, and compatible with direct contact with natural water. Its mechanical properties are highly similar to those of the prototype concrete. Based on a 1:70 geometric scale, a shaking table model test of the concrete gravity dam-reservoir system was conducted. The dynamic response and damage evolution under empty and full reservoir conditions were compared and analyzed. The study shows that this material can accurately simulate the stress-strain relationship and failure mode of prototype concrete. Under the full reservoir condition, the dam’s fundamental frequency showed only a 2.72% deviation from the numerical simulation, and as the seismic excitation amplitude increased, the changes in the fundamental frequency effectively reflected the accumulation of damage. Under the design seismic motion, the measured accelerations and stress responses for both empty and full reservoir conditions were in good agreement with numerical calculations. Under overload conditions, the acceleration amplification factor at the dam crest decreased with damage accumulation, and the dam neck was identified as the seismic weak zone. As the peak ground acceleration (PGA) increased from 0.15 g to 0.70 g, the fundamental frequency changes effectively reflected the damage accumulation process in the dam, while the hydrodynamic pressure at the dam heel showed a linear increase (457% increase). The experimentally measured hydrodynamic pressure distribution was between the rigid dam and elastic dam hydrodynamic pressures, reflecting the real fluid-structure interaction effect. This study provides a reliable material solution and data support for dam seismic physical model testing. Full article

Rock geotechnical properties can be reflected in drill signals while drill rod penetrates through rocks. The rate of penetration, rotary speed, torque, load, sound, vibration, etc., are different for various rock types, since they are influenced by rock properties. Therefore, a close analysis and derivations of these drill signals can provide valuable insights into rock geotechnical properties. The drill returned signals from the mechanical sensors; for example, torque and load are commonly interpreted to characterize the rock properties. There are still limitations to such sensors and interpretation methodologies that can confidently characterize rock properties. In this research, mechanical sensors were compared and complemented with seismic sensors, for example, accelerometers and geophones, to characterize rocks and interfaces. This paper presents experimental results conducted with synthetic rock samples using mechanical and seismic sensors with a field scale drilling machine. The results show that seismic sensors can identify voids or weak (fractured) interfaces clearly compared to mechanical sensors. Smaller gaps have smaller span of low frequency and vice versa. The sensors attached to the drill head were less sensitive than the sensors attached to the sample. Drill signals showed the capacity to effectively identify material interfaces and weak fractures up to 4 mm thick, with geophones providing clearer data than accelerometers. Neither sensor distinguished fractured zones from voids. Sensors mounted directly on the sample were more sensitive than those attached to the drill head, likely due to vibration-induced signal attenuation at the drill head. Full article

The marine carbonate reef–shoal reservoirs in the gentle slope platform margin of the M block, eastern Sichuan Basin, were well developed during the Changxing Period in late Permian and represent a favorable carbonate reservoir play for petroleum exploration. The lack of effective research methods has hindered the analysis of their unique sedimentary characteristics and controlling factors. Based on cores, thin sections, well logs, testing analyses, and high-resolution 3D seismic data, this study analyzes the lithological associations, microfacies types, reservoir physical properties, and seismic reflection characteristics of reef–shoal reservoirs. On this basis, the reef–shoal sedimentary characteristics and controlling factors were analyzed. The main conclusions are as follows: (1) Two major categories and eight subcategories of petrography were identified in marine carbonate reef–shoals, and five microfacies were identified: reef base, reef core, reef flank, reef-top–shoal, and inter-reef sea. Among these, the reef-top–shoal constitutes the optimal reservoir, while the reef flank develops secondary reservoirs. (2) The reef–shoals exhibit an external mound or wedge-shaped reflection, with internally discontinuous or chaotic reflections. Discontinuous reflections are observed at the top, while onlap terminations are present on its flanks. (3) The vertical accretion of the marine reef–shoals is small, but the platform margin belt is wide in planar, multiple rows reef–shoal bodies are identified, reflecting their small scale, discrete planar distribution, rapid lateral migration, and diverse stacking patterns. (4) The regional gentle slope marine platform margin geological setting, tectonic paleogeomorphology, and high-frequency sea level fluctuation collectively control the sedimentary structure and the formation of high-quality reservoirs of the marine reef–shoal complex. This research provides guidance for petroleum exploration and favorable reservoir prediction in the marine carbonate reservoirs of the Sichuan Basin. Full article

Understanding the mechanisms of hydrocarbon migration, accumulation, and alteration, particularly how evolution controls these processes, is critical for exploring lithologic hydrocarbons in reservoirs. In the complex tectonic settings of the continental margin of the stable North China Craton, there is a significant presence of small yet highly prolific hydrocarbon reservoirs. The processes of hydrocarbon migration and accumulation are complex and thus represent an important research focus in geology. This study, based on core, logging, and seismic data and integrating fluid inclusion analysis, quantitative fluorescence techniques, and geochemical experiments, combines the shale smear factor and paleotectonic reconstructions to clarify the hydrocarbon accumulation episodes, migration pathways, and factors controlling reservoir adjustments in the Yanwu area of the Tianhuan Depression in the Ordos Basin, China. The results reveal three types of NE-trending left-lateral strike–slip faults: linear, left-stepping, and right-stepping. Shale Smear Factor (SSF) analysis confirms that these faults exhibit segmented opening behaviors, with SSF > 1.7 identified as the threshold for fault openness. Multiparameter geochemical tracing based on terpanes and steranes shows that lateral migration along fault zones dominates the preferential migration pathways for hydrocarbons. Fluid inclusion thermometry revealed homogenization temperatures within the 100–110 °C and 80–90 °C intervals, while the oil inclusions exhibit blue or blue-and-white fluorescence, reflecting early hydrocarbon charging and late-stage secondary migration. Integrated analysis indicates that during the late Early Cretaceous (105–90 Ma), hydrocarbons were charged upward through open segments of linear strike–slip fault zones in the northern study area, experiencing lateral migration and accumulation along high-permeability sand bodies and unconformities in the shallow strata. Since the Late Cretaceous (65 Ma-present), the regional tectonic framework has evolved from a west–high, east–low to a west–low, east–high configuration, inducing secondary hydrocarbon migration and leading to the remigration or even destruction of early-formed oil reservoirs. This study systematically demonstrates that fault activity and tectonic evolution control the accumulation and distribution of hydrocarbons in the region. These findings provide theoretical insights for hydrocarbon exploration in regions with complex tectonic evolution within stable cratonic basins. Full article