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This paper uses shake table tests to study tunnel landslide failures in earthquake zones under four conditions: (GK1) the tunnel intersects the sliding mass, (GK2) the tunnel is perpendicular to the sliding surface, (GK3) the tunnel is positioned below the sliding surface, and (GK4) the tunnel is situated above the bedrock. The dynamic responses under the four conditions are analyzed using time-domain strain analysis methods. Additionally, from an energy perspective, the amplified Arias intensity (MIa) is employed to characterize the cumulative deformation damage of the tunnel lining. The results indicate that under four working conditions, the upper landslide region of the tunnel landslide system exhibits a "settlement-compression-shear" type of sliding failure. However, in conditions GK1 and GK2, where the lining structure is present, the tunnel lining provides additional support to the landslide, resulting in less severe damage to the slope compared to conditions GK3 and GK4. However, under conditions GK1 and GK2, the left sidewall of the tunnel lining experiences more severe damage due to landslide pressure. The maximum soil pressure and bending moment on the left sidewalls in GK3 and GK4 are only 40–60% of those observed in GK1 and GK2. In addition, based on the trend of MIa, the cumulative deformation evolution of the tunnel lining can be categorized into three stages: the initial stage (0.1–0.2 g), the progressive deformation stage (0.2–0.4 g), and the failure deformation stage (0.4–0.6 g). Further research confirms that under seismic action, the slope experiences a significant progressive catastrophic evolution. This process is characterized by typical seismic cumulative damage effects, with sustained seismic loading causing deformation and damage to gradually expand from localized areas to the entire slope. This continuous fatigue effect progressively weakens the stability of the lining structure, ultimately leading to its failure. Therefore, the deformation and damage of the slope under seismic loading pose a serious threat to the safety of tunnel linings, highlighting the need for close attention to their long-term stability. The research results provide a scientific basis for reinforcing tunnel linings in earthquake-prone mountainous areas. [ABSTRACT FROM AUTHOR]

The southeastern margin of the Tibetan Plateau is a crucial region to understand the mechanisms of plateau uplift and deformation. This region is seismically active and has experienced multiple large earthquakes, resulting in significant human and economic losses. Constructing velocity and anisotropic tomography models is crucial for understanding the seismogenic mechanism and deep structural deformation in this area. In this study, we extract high-quality P-wave first-arrival data from the earthquake catalog of the China Earthquake Administration and use them to construct both common-receiver and common-source differential traveltime datasets. We then apply a novel adjoint-state traveltime tomography approach to obtain new P-wave velocity and azimuthal anisotropy models for the region. This method eliminates the need for ray tracing, thereby reducing the potential bias from the ray theory and ray tracing. A comparison between our results and previous imaging models and shear-wave splitting measurements reveals several new details. The results indicate weak anisotropy in the shallow depth of the central Chuandian block. Two low-velocity anomalies are identified beneath the Songpan-Ganzi and Lijiang-Xiaojinhe fault zones, as well as beneath the Xiaojiang Fault. The distinct anisotropic characteristics of these two low-velocity anomalies suggest different tectonic contexts: Beneath the Songpan-Ganzi and Lijiang-Xiaojinhe fault zones, the azimuthal anisotropy aligns north-south and northeast-southwest, while beneath the Xiaojiang Fault, it aligns northwest-southeast. In addition, the anisotropy of the upper mantle in the southern part of the study area has a significant east-west feature. The earthquake relocation results reveal intensified seismic activity in regions with significant velocity contrasts and near fault zones. Segmental seismic activity is observed along some major fault zones, and seismicity is also more pronounced in fault intersection areas. The new imaging results provide new perspectives and insights for understanding the seismogenic mechanisms and regional tectonic deformation in the region. [ABSTRACT FROM AUTHOR]

In this research, we conducted the numerical simulation of the tsunami, and the static stress transfer of Coulomb for the 1960 northern Peru earthquake (Mw 7.6). The Tsunami numerical model was used to simulate the propagation and inundation processes. In the inundation grid, we used a high resolution bathymetry (30m resolution) from marine sounding. For the inundation grid (grid D), the results of simulated model are parameters such as arrival times of the first wave of the tsunami, maximum wave heights and inundation areas for each zone to be modeled. These results have been validated with information provided by the population that endured the effects of the earthquake and subsequent tsunami. The simulated arrival times of the leading wave for the areas of San José, Pimentel, Santa Rosa and Puerto Eten were 69.5, 69, 66.5 and 68min, respectively. The maximum inundation in San José was 2.78km away and the height of the wave reached approximately 6.2m. The Coulomb stress transfer indicates an increase in stress in the northern zone of the seismic source close to Piura coast, as well as an increase in stress between the Peruvian trench and the seismic source near the meridians −81.0∘ and −81.5∘ which implies an activation of seismicity and a potential zone for a next seismic event of similar or greater magnitude. [ABSTRACT FROM AUTHOR]

This paper presents a complete map of the Mesozoic volcanic-plutonic complexes in the Taiwan Strait and its adjacent areas in terms of seismic profiles, ages, geochemistry, isotopic systematics, and published data. Two periods of igneous activity in the Taiwan Strait can be distinguished by seismic profiles: Jurassic (200.4–148.2 Ma); and Latest Jurassic/Cretaceous to Maastrichtian (144–66 Ma), of which the Cretaceous is the best preserved and could possibly be the most widespread. Mesozoic magmatic activity with the NE-striking distribution was migrating southeastward (oceanward). LA-MC-ICPMS zircon U – Pb dating yields the age data of 109.5 ± 0.4 Ma for PTDH1 granodiorite and 92.6 ± 0.4 Ma for PTDH4 rhyolite in the Taiwan Strait, respectively. The 581.66-m-thick Upper Jurassic volcanic rocks of the Chuan2 well are the thickest Mesozoic igneous rocks in the Taiwan Strait. The petrogenetic discrimination diagram of the Cretaceous volcanic-plutonic complexes along the coast of South China and the Taiwan Strait generally is belonging to volcanic arc or intraplate type calc-alkaline rock series. The high potassium calc-alkaline rock series of the Cretaceous volcanic-plutonic complexes that is most widely distributed in the coastal areas of South China and the Taiwan Strait. They are controlled by the subduction of the Palaeo-Pacific domain. [ABSTRACT FROM AUTHOR]

Fault displacement hazard, along with ground shaking hazard and earthquake-induced geohazard, are the primary forms of disaster in major earthquakes. Buildings located on areas of strong seismic surface displacement are likely to be damaged if anti-displacement design is not carried out. Therefore, a reasonable and targeted active fault classification scheme is helpful for avoidance and anti-displacement hazard of active fault in engineering construction. However, the existing classification schemes are rough, and some have no quantitative classification basis, which makes it difficult to apply these classification schemes in actual work. Also, they did not specify whether all active faults should be avoided. In this paper, considering the physical mechanism of earthquakes, using two activity parameters of active faults, "strong earthquake recurrence period" (TRP) and "strong earthquake elapsed time ratio" (Ret), and referring to the probabilistic seismic hazard analysis method (PSHA), the maximum magnitude of potential earthquake on the fault under different exceedance probabilities (EP) is calculated, and was divided into six levels. The fault displacement hazard level under different exceedance probabilities may be different. For buildings with different importance levels, we recommend six hazard classification schemes with different exceedance probabilities. Standard buildings should avoid active faults with a fault displacement hazard level of Ⅰ ~ Ⅲ (faults that can generate earthquakes of magnitude m0 and above under a 4% exceedance probability over 100 years). Special buildings and key buildings should avoid active faults with a fault displacement hazard level of Ⅰ ~ Ⅳ (faults that can generate earthquakes of magnitude m0-0.5and above under a 1% exceedance probability over 100 years). The fault displacement hazard classification scheme given in this paper takes into account the physical mechanism of earthquake occurrence and the importance of buildings, which makes this classification scheme both scientific and practical, helps provide technical support for the design and construction of buildings. This study is still quite preliminary, and there are many issues that need further study. [ABSTRACT FROM AUTHOR]

This study investigated the seismic sensitivity of tunnels in the Jammu Region (JR) of the northwestern Himalayas, a region characterized by significant seismic activity and complex geological conditions. The research combined both analytical and numerical approaches to assess the influence of site conditions, tunnel lining, and reinforcement properties on tunnel resilience. A key objective is to develop a more reliable seismic assessment method by adopting a P-wave-based approach, which is particularly suitable for mountainous tunnels prone to landslides. The study identified three seismic hazard zones, with peak ground accelerations (PGA) ranging from less than 0.3 g to greater than 0.5 g, providing vulnerability aspects. The major outcomes of this study include guidelines for the design and retrofitting of sustainable and resilient underground structures in the Himalayas, with broader implications for global projects in seismically active and geologically complex regions. The methodologies and insights can be applied to infrastructure projects worldwide, enhancing the safety of communities living in vulnerable areas. This work aligns with the United Nations Sustainable Development Goals (SDGs), particularly in promoting resilient infrastructure and sustainable development, contributing to both structural resilience and the geological safety of the Himalayan region. [ABSTRACT FROM AUTHOR]

In this paper, we review the theoretical studies of the electromagnetic and other non-seismic phenomena accompanying earthquakes. This field of geophysical research is at the interception of several sciences: electrodynamics, solid-state physics, fracture mechanics, seismology, acoustic-gravity waves, magnetohydrodynamics, ionospheric plasma, etc. In order to make physics of these phenomena as transparent as possible, we use a simplified way of deriving some theoretical results and restrict our analysis to order-of-magnitude estimates. The main emphasis is on those theoretical models which give not only a qualitative, but also a quantitative, description of the observed phenomena. After some introductory material, the review is begun with an analysis of the causes of local changes in the rock conductivity occasionally observed before earthquake occurrence. The mechanisms of electrical conductivity in dry and wet rocks, including the electrokinetic effect, are discussed here. In the next section, the theories explaining the generation of low-frequency electromagnetic perturbations resulting from the rock fracture are covered. Two possible mechanisms of the coseismic electromagnetic response to the propagation of seismic waves are studied theoretically. Hereafter, we deal with atmospheric phenomena, which can be related to seismic events. Here we discuss models describing the effect of pre-seismic changes in radon activity on atmospheric conductivity and examine hypotheses explaining abnormal changes in the atmospheric electric field and in infrared radiation from the Earth, which are occasionally observed on Earth and from space over seismically active regions. In the next section, we review several physical mechanisms of ionospheric perturbations associated with seismic activity. Among them are acoustic-gravity waves resulting from the propagation of seismic waves and tsunamis and ionospheric perturbations caused by vertical acoustic resonance in the atmosphere. In the remainder of this paper, we discuss whether variations in radon activity and vertical seismogenic currents in the atmosphere can affect the ionosphere. [ABSTRACT FROM AUTHOR]

The identification of areas that are susceptible to damage due to earthquakes is of utmost importance in tectonically active regions like Northeast India. This may provide valuable inputs for seismic hazard analysis; however, it poses significant challenges. The present study emphasized the integration of Interferometric Synthetic Aperture Radar (InSAR) deformation rates with conventional geological and geophysical data to investigate earthquake damage susceptibility in the Barapani Shear Zone (BSZ) region of Northeast India. We used MintPy v1.5.1 (Miami INsar Timeseries software in PYthon) on the OpenSARLab platform to derive time series deformation using the Small Baseline Subset (SBAS) technique. We integrated geology, geomorphology, gravity, magnetic field, lineament density, slope, and historical earthquake records with InSAR deformation rates to derive earthquake damage susceptibility using the weighted overlay analysis technique. InSAR time series analysis revealed distinct patterns of ground deformation across the Barapani Shear Zone, with higher rates in the northern part and lower rates in the southern part. The deformation values ranged from 6 mm/yr to about 18 mm/yr in BSZ. Earthquake damage susceptibility mapping identified areas that are prone to damage in the event of earthquakes. The analysis indicated that about 46.4%, 51.2%, and 2.4% of the area were low, medium, and high-susceptibility zones for earthquake damage zone. The InSAR velocity rates were validated with Global Positioning System (GPS) velocity in the region, which indicated a good correlation (R2 = 0.921; ANOVA p-value = 0.515). Additionally, a field survey in the region suggested evidence of intense deformation in the highly susceptible earthquake damage zone. This integrated approach enhances our scientific understanding of regional tectonic dynamics, mitigating earthquake risks and enhancing community resilience. [ABSTRACT FROM AUTHOR]

The extraction of geothermal energy is associated with induced seismicity. Depending on the extraction parameters, such as injection pressure and volume, the induced seismicity is time-dependent. We investigate the case of the two geothermal power plants of Insheim and Landau, which are located in the Upper Rhine Graben in Southwest Germany. The induced seismicity was observed by a local seismic network consisting of a total of 19 stations, resulting in an earthquake catalog comprising 930 events for the Landau reservoir and 1985 events for the Insheim reservoir, both between 2012 and 2022. Based on this earthquake catalog, seismic source areas are defined for both reservoirs, and a probabilistic seismic hazard assessment (PSHA) is performed. Using temporal subsets of the earthquake catalog, PSHA can also be performed for shorter time ranges, resulting in larger expected PGV values in times of higher induced seismicity. The seismic velocity profiles obtained by site effect studies based on ambient seismic noise measurements highlight relatively large variations of the site effects on short scales in the area. The consequences of these lateral variations on the seismic hazard assessment are also discussed. [ABSTRACT FROM AUTHOR]

Intensity prediction equations (IPEs) are critical for quickly obtaining the macroscopic intensity of a site post-earthquake, with regional dependencies influencing their design. Historically, most IPEs in China have focused primarily on the factors of distance and magnitude. This study develops site-specific IPEs for Western China, using data from 53 seismic events since 1970, to address the previously overlooked importance of site conditions and overcome the limitations of past models. The data were categorized into three site groups, with IPEs derived through multiple nonlinear regression methods. Our findings reveal that macroscopic intensities at category III and IV sites are notably higher than those at categories I and II, with this disparity increasing alongside the magnitude. Unlike conventional IPEs, the IPEs proposed in this paper incorporate local geological and seismological characteristics, enhancing prediction accuracy across varied site conditions. This methodology distinctly contrasts with prior approaches by providing a nuanced assessment that integrates comprehensive site categorization, resulting in more precise intensity predictions. This advancement is particularly crucial for effective emergency management and disaster mitigation strategies in seismically active regions. [ABSTRACT FROM AUTHOR]

The Zagros collision zone, located in the southwest of Iran, is experiencing an immoderately large number of seismic hazards caused by the convergence between the two Arabia and microplate of central Iran. The coda Q has been widely used as a vital parameter to investigate the different tectonic features as well as seismic risk assessments. In this study, we have analyzed the spatial variation of coda wave attenuation in the Zagros region, to evaluate different geological features affecting the seismic wave's propagation. Our dataset comprises 87,295 coda records of about 6421 local earthquakes, with magnitude greater than three recorded by 36 seismic stations in the period of 2006–2020. We have applied a very simple Q c regionalization method to mapping spatial distribution of Q c in Zagros area. The spatial distributions of coda have a positive correlation with the tectonically and lithology of the interested area. According to the results, three primary elements have been suggested as major controlling factors of variation of seismic Coda waves in different parts of the Zagros area. These factors include: (1) intra-crustal relamination process (crustal channeling), (2) 12 km thickness of sediment-filled by fluid (oil and gas) and (3) Hormoz salt (salt domes). Our results of coda wave attenuation, coupled with the findings from 3D velocity tomography which revealed significant velocity variations across the Main Zagros Reverse Fault (MZRF), particularly toward the Sanandaj-Sirjan zone, suggests a potential influence of the fault zone on seismic wave propagation characteristics. [ABSTRACT FROM AUTHOR]

The accurate identification of the characteristics of joints, fractures, extensions, and slips within the slope under earthquake action is essential for understanding the potential failure modes of bedding rock slopes (BRS). In this paper, an innovative method for separating low-frequency seismic response signals (LFSRS) and high-frequency rock damage signals (HFRDS) using VMD-HT was developed, and an index for identifying BRS internal damage using HFRDS was proposed. Three typical BRS cases types-blocky, soft-hard interbedded, and weak intercalation-included in the high seismic intensity area of southwest China were selected to prove the proposed method for separating damage signals. The seismic discrete element numerical modeling was utilized to analyze the crack development and damage evolution characteristics, and illustrate the patterns of seismic instability evolution in BRS. Through a comprehensive analysis of the time-domain, frequency-domain, and time–frequency domain signal characteristics, it was confirmed BRS exhibit a combination of LFSRS and HFRDS resulting from rock structural plane cracking and rock block collisions. The damage identification capability of the peak of marginal spectrum amplitude was assessed for LFSRS, proving its capability in locating damage and evaluating the distribution of seismic energy but failed to detect minor damage and determine the timing of damage occurrence accurately. The instantaneous high-frequency energy level index (IELh) was introduced using HFRDS, enabling the identification of crack initiation and propagation locations within the slope and pinpointing the moment of crack appearance. A quantitative relationship between the IELh index and the damage degree was finally established. The findings of this study are highly significant for the in-depth exploration of the seismic failure mechanism of the BRS landslide from the perspective of energy-based transmission characteristics. [ABSTRACT FROM AUTHOR]

We built a regional geological section founded upon the assessment of a seismic line in the Volturno basin, which is situated on the northern Campania continental shelf of the Tyrrhenian margin of Southern Italy. This section has been integrated with multichannel seismic data of Zone E (ViDEPI project) to highlight its relationships with the Massico structure. In the Volturno basin, there are four Pleistocene to Holocene units, recognized based on seismic analysis lie above deep seismo-stratigraphic units, related to Campania Latium carbonate platform and The Frosinone Flysch. Onshore and offshore seismic data, calibrated with lithostratigraphic correlation, have displayed the seismo-stratigraphic framework, including both sedimentary and volcanic seismo-stratigraphic units. Of these, the lavas associated with the Northern Campania Volcanic Zone's Villa Literno volcano are associated with seismic unit 2a. Seismo-stratigraphic data has shown the offshore prolongation of the Massico structure, as involved by normal faults and flower structures. The whole-data interpretation suggests that the tectonic activity acted in correspondence to normal faults, which have controlled half-graben and interposed structural highs, fitting to the regional geological setting of the continental margin. [ABSTRACT FROM AUTHOR]

A large number of seabed depressions, covering an area of 2500 km2 in the Xisha Massif of the South China Sea, are investigated using newly collected high-resolution acoustic data. By analyzing the morphological features and seismic attributes of the focused fluid flow system, five geological structures are recognized and described in detail, including pockmarks, volcanic mounds, pipes, faults, and forced folds. Pockmarks and volcanic mounds occur as clustered groups and their distributions are related to two large-scale volcanic zones with chaotic seismic reflections. Pipes, characterized by disordered seismic reflections, mainly occur within the focused fluid flow zone (FFFZ) and directly link with the large-scale deep volcano and its surrounding areas. Faults and fractures mainly occur along pipes and extend to the seafloor, commonly presenting lateral walls of mega-pockmarks. Forced folds are primarily clustered above volcanic zones and commonly restricted between faults or pipes, characterized by sediment deformations as indicated in seismic profiles. By comprehensive analysis of the above observations and a simplified simulation model, the volcanism-induced hydrothermal fluid activities are argued herein to contribute to these focused fluid flow structures. In addition, traces of suspected submarine instability disasters such as landslides have been found in this sea area, and more observational data will be needed to determine whether seafloor fluid flow zones can be used as a predictor of seafloor instability in the future. [ABSTRACT FROM AUTHOR]

Paleoseismic studies are essential to improve earthquake hazard mitigation, a challenging task in the Tian Shan mountains characterized by numerous active faults, frequent strong earthquakes, and abundant triggered landslides. Here, we date the debated formation of Kaindy Lake, the famous landslide-dammed lake in southeastern Kazakhstan, included in the UNESCO World Network of Biosphere Reserves. Our dendrochronological study compares ring-width patterns from dead trees (Picea schrenkiana) still standing in the lake with living trees growing on surrounding slopes and other trees on the landslide debris. Our results place the formation of the lake to just after 1888 A.D. (the last ring of sunken trees) and before 1898 A.D. (the first established trees on the landslide), a period for which only the 1889 A.D. Chilik earthquake (M 8.2) has been reported and caused extensive damages in the region (surface ruptures, landslides). Thus, we propose that the landslide was triggered during this historical earthquake, questioning the previously preferred date of 1911 A.D., and the local common belief. Furthermore, our results indirectly complement previous paleoseismic studies at 8.5 km away, for which the most recent event in the region was poorly defined by geochronological dating, but suggested a surface rupture associated with the 1889 A.D. earthquake. The proximity of the landslide to the surface rupture would place it in the epicentral zone of the Chilik earthquake. [ABSTRACT FROM AUTHOR]

Broadband seismogram synthesis of the multi-layer and multi-scale has been a longstanding focus in seismic engineering area for decades, which also has many difficulties to overcome in computing range and efficiency. This paper proposes the direct exact stiffness matrix method, a form of the frequency-wavenumber method (abbreviated as fk), for synthesizing seismograms. First, the direct exact stiffness matrix of the multi-layered and multi-scale underground structure is constructed in the frequency-wavenumber domain, and the sub-fault source (the earthquake fault is divided into the sub-fault source) is equivalent to the displacement-stress discontinuity to describe the dislocation. Furthermore, the "direct stiffness method" is used to determine the receiver's motion, which establishes Green's function (the relationship between the source and the receiver). The divergence index term in the stiffness matrix is modified to overcome the solution inefficiency associated with the thick layer and the high-frequency. The accuracy is verified by comparing the proposed method results with three examples in the publications, involving different source types and depth scales. The kinematics hybrid source model, based on the GP14.3 model, is introduced to generate a finite fault source model. The 2023 Turkey Mw 7.8 earthquake source model is established, and the applicability of the fk method in the near-fault seismic simulation is validated by comparing it with the time history and spectrum records. The Mw 7.0 dip-slip fault source model is based on the GP14.3 hybrid source generation which is set in a multi-scale layered half-space. The study area comprises a near-fault area with 122 receivers. Conclusions are drawn based on the analysis of the normalized response spectrum, peak spectral acceleration, and difference rate by changing the shallow velocity structure. The results show that the shallow velocity structure results in an average amplification of 5.1% in the fault-parallel direction and 7.1% in the fault-perpendicular direction. [ABSTRACT FROM AUTHOR]

After a major earthquake, there is often high risk of fires, which can exacerbate the threat to people and property. To investigate the fire spread characteristics in the aftermath of earthquakes, an integrated simulation approach is introduced in this study. A simulation procedure, which combines elastoplastic time history analysis with the cellular automata (CA) model, is designed to sequentially model the earthquake-induced damage to groups of buildings and the ensuing fires. The earthquake damage state of each building is determined through elastoplastic time history analysis using an earthquake disaster simulator (Yousimulator) and is integrated into the key input parameters of the cellular automaton (CA) model. Combined with the detailed properties of the building and real-time meteorological conditions, the dynamic spread behavior of fires after earthquakes is simulated. To validate the simulation procedure, the 1995 Kobe earthquake-related fires in Japan were simulated, and the results were compared with the actual fire conditions. The results showed that the overall spread pattern and reach of the simulated fires are similar to those of the actual fires. Moreover, the simulation procedure demonstrated notable efficiency, completing the simulation within only five minutes. This simulation procedure provides a valuable means to assess the post-earthquake fire risk in urban areas. By leveraging this method, decision-makers can effectively evaluate the vulnerability of the urban environment to post-earthquake fires, enabling them to make informed decisions and implement targeted measures to mitigate such risks. [ABSTRACT FROM AUTHOR]

The bolt axial force of high-strength bolted frictional glass fiber–reinforced polymer (GFRP) joints is reduced by the viscoelastic behavior of the GFRP matrix resin. In this study, the long-term relaxation characteristics of GFRP joints with hot-dip galvanized, coated connecting plates were clarified. Long-term relaxation tests were performed by varying the connecting conditions and material properties, such as the presence or absence of the GFRP coating, applied bolt axial force, presence or absence of hot-dip galvanization and surface treatment of the connecting plates, GFRP base member thickness, and fiber content. Phosphate treatment of the galvanized steel plates exhibited a negligible effect on the relaxation properties of GFRP joints. The bolt axial force reduction rate was accelerated by utilizing hot-dip galvanized plates or GFRPs with low fiber contents. This study provides insights into the long-term relaxation characteristics of GFRP joints with specific coatings, thus contributing to safer, more durable, and cost-effective infrastructure solutions, while also fostering advancements in materials science and engineering. Practical Applications: This research examined the changes in bolted joint strength in fiber-reinforced polymer (FRP) structures over time due to various factors such as bolt type, joint material, and environmental conditions. Our findings revealed that even after 30 years, the joints maintain strength well above the standard required, ensuring long-term reliability. This is particularly important for structures for which safety and durability are crucial, such as bridges and buildings in seismic areas. The study also highlights that specialized coatings and treatments, such as phosphate or galvanized surfaces, have a minimal effect on joint strength. This suggests that simpler, cost-effective methods can be employed without compromising safety. This has practical implications for construction and maintenance, offering ways to extend the life of existing structures and reduce the costs for new ones. By understanding these factors, engineers can design safer, longer-lasting FRP joints, contributing to more sustainable infrastructure development. This research provides valuable insights into enhancing the longevity and performance of bolted joints, ensuring that these critical connections withstand the challenges posed by time and environmental factors. [ABSTRACT FROM AUTHOR]

This study investigates the durability of concrete structures under severe environmental conditions, focusing on the effects of thermal stress, saline exposure, and seismic activity. The research employs a dual approach, combining laboratory experiments and field case studies to analyze various environmental impacts, mix designs, and the use of crystalline admixtures. Two concrete mix designs, CMD-01-C30/37 (mass concrete) and CMD-02-C35/45 (underwater concrete), were developed and tested for strength, permeability, and self-healing properties. The results demonstrate that both mix designs met or exceeded the required strength specifications, with improved resistance to water penetration and permeability depths lower than the code requirements set by European standards from EC2. The incorporation of crystalline admixtures in the mix designs significantly enhanced durability and performance, aligning with the priority of developing zero-carbon concrete solutions. The study also observed the self-healing capabilities of concrete treated with crystalline admixtures, as evidenced by the sealing of cracks at expansion and construction joints over time. These findings contribute to the development of a robust methodology for creating resilient structures adaptable to climate change, with potential implications for enhancing seismic resistance and structural longevity. The study underscores the importance of considering environmental factors and innovative admixtures in concrete design to improve durability and resilience, particularly in areas prone to seismic activity and extreme environmental conditions. Future research directions should focus on further investigating self-healing mechanisms, exploring the integration of durable and self-healing cement-based materials in engineering practice, and evaluating applications for both new construction and retrofitting existing structures. [ABSTRACT FROM AUTHOR]

Tunnels crossing active faults frequently experience simultaneous exposure to fault dislocation and seismic action during operation. To study the damage behavior of tunnels under the combined effects of fault dislocation and seismic action, a three-dimensional nonlinear finite element model was established. This model simulates fault dislocation superimposed on seismic action in the context of tunnel engineering through active faults. The main conclusions are as follows: (1) The acceleration amplification phenomenon occurs in the tunnels after the superposition of seismic action; at the same time, the degree and scope of tunnel damage increase significantly, in which the increase in tensile damage is more significant. (2) The initial damage from fault dislocation worsens tunnel damage under seismic action, as evidenced by the energy dissipation characteristics. (3) As the initial fault displacement and peak seismic acceleration increase, the extent of lining damage also increases. Notably, compressive damage to the lining is symmetrically distributed along the fault plane, whereas tensile damage is significantly more severe within the fault rupture zone. (4) Even moderate earthquakes can cause severe damage to tunnels crossing active faults. Therefore, tunnel construction in these areas must include disaster prevention and mitigation strategies. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the performance of the United States Geological Survey velocity model developed for the San Francisco Bay Area (SFBA), version 21.1. The evaluation was performed through high-resolution three-dimensional physics-based ground motion simulations of seven small-magnitude earthquakes (ranging from magnitude 3.8 to 4.4) that occurred on the eastern side of the San Francisco Bay. The simulations were performed in the frequency range from 0 to 5 Hz with a minimum shear-wave velocity of 250 m/s, which allowed the capture of wave propagation effects of the near-surface soft materials that characterize local basins. Based on the direct comparison of Fourier amplitude spectra between recorded and simulated ground motions for more than 250 stations, we found that the velocity model generally performs well in the frequency range of 0.2–5 Hz. The median value of the Fourier amplitude residuals was found to be near zero for all seven earthquakes. The slight over-prediction of 0.2 log-natural units at frequencies above 3 Hz in our simulations was attributed to the potentially inaccurate representation of the source radiation pattern by a double-couple point source model, and simple representation of shallow small-scale underground structural complexity in the velocity model. Maps of spectral amplitude differences between the simulated and recorded data were used to identify areas responsible for systematic ground motion over-predictions or under-predictions. For example, while some sub-domains over soft sediments show over-prediction patterns, the block east of the Hayward fault is prone to exhibit patterns of under-prediction. These maps can be used to guide future refinements of the SFBA velocity model. Since our simulation methodology allows for the decoupling of the source and wave propagation effects, the ground motion data generated by our simulations can also be used to quantify the epistemic uncertainty due to the velocity model, in empirically based ground motion estimates for the SFBA. [ABSTRACT FROM AUTHOR]

Recent advancements in computer science and data-driven decision making have greatly decreased the impact of natural disasters on civilization. The Western zone of Surat, a city in Gujarat, India, is examined as a study area to assess the seismic vulnerability of the structures using the capacity spectrum method. A thorough field survey was carried out in the Western zone of Surat to create detailed building stock inventory. The building information was gathered through a comprehensive field survey, which involved collecting, organizing, enhancing, and finalizing the data. The data were determined based on factors, such as the building's height, material, configuration, and year of construction. The seismic hazard in the city's area is described using response spectra based on Indian seismic provision IS 1893: Part-I for seismic zone-III. According to the survey, the majority of the buildings in the Adajan area are special moment-resisting reinforced concrete (RC) building frame structures. ArcGIS Pro software is utilized to manage collected information for developing seismic vulnerability scenarios. The results indicate that midrise building structures designed according to older versions of the seismic codes are more susceptible to lateral damage. The results of the cluster mapping analysis carried out in the Western region help pinpoint the urban area that is vulnerable to seismic activity at a local regional level. Practical Applications: This study presents a new method for evaluating the susceptibility of structures to seismic events by measuring the level of uncertainty, denoted by the factor β , estimated for seismic standards in India. Doing so allows for more precise forecasts of structural harm on a regional scale, which is essential for metropolitan regions such as Surat, where rapid urbanization and a dense population contribute to heightened seismic vulnerabilities. Our research utilizes the capacity spectrum method to offer practical insights for urban planners, engineers, and policy-makers in identifying and prioritizing buildings at risk and needing upgrading. This approach conforms to local norms and improves the predicted precision of seismic evaluations, rendering it an essential instrument for disaster management and safety inspections. Applying these findings in practice can make urban areas more resistant to seismic activities, significantly reducing the risks and protecting residents from potential damages. This study cultivates a culture of readiness and advocates for elevated building safety standards, thus enhancing the safety and sustainability of places prone to seismic activity. [ABSTRACT FROM AUTHOR]

The precise position and geometry of a fault and the recognition of contemporary active strands are pivotal elements for formulating regulations for earthquake fault zones and fault setbacks. The western frontal escarpment toe of the Coastal Range in Tapo, eastern Taiwan is commonly considered as the plausible location of the N18°E-trending, east-dipping Chihshang creeping seismogenic fault. Frontal collapse and flattening of reverse faulting, in addition to fluviation and landslide have complicated the process for defining the Chihshang fault configuration. We used a multidisciplinary approach, combining site investigation, geological core analysis and correlation, resistivity prospecting, and inclinometer monitoring, to illuminate the subsurface structure and deformation of the leading edge of the Chihshang fault at Tapo Elementary School. We found that (1) the Chihshang main fault is a contact of alluvium deposits and the mudstone of Lichi mélange, and has a dip angle of approximately 77° within the resistivity gradation zone 55 m east of the toe of the geomorphic escarpment; (2) it has a 2-year cumulative horizontal displacement of 20.7 mm northwestward and continuously creeps without seasonal variation; and (3) the active deformation on the escarpment results from a combined effect of fault creeping and slow gravity sliding of the mass which is steadily supplied by the Chihshang reserve faulting. A mechanism of faulting-relay landsliding is proposed to understand the active deformation on the escarpment. Great caution is needed in the interpretation of the aseismic surface ruptures along the inferred trace of reverse creeping faults as fault branching. Highlights: The Chihshang fault with a dip angle of 77° is located 55 m east of the escarpment toe, which was once thought to be fault trace in Tapo. The fault has a left-lateral slip rate of 8.2 mm/year and a transverse slip rate of 6.4 mm/year and continuously creeps without seasonal variation. A mechanism of faulting-relay landsliding is proposed to interpret the active deformation on the escarpment at Tapo Elementary School. [ABSTRACT FROM AUTHOR]

The Vrancea Seismic Zone (VSZ) is an atypical intermediate-depth earthquake nest located in the South-East Carpathians in Romania, often regarded as a relic slab sinking into the mantle. The origin of the slab and the earthquakes it produces are debated because brittle failure is unlikely to occur at mantle depths. Cluster types and statistical properties of seismicity can vary with deformation regime, fluid content and temperature. Here we investigate the spatial–temporal properties of earthquakes recorded in the VSZ from a high-quality local catalogue, identify and classify earthquake clusters, placing constraints on the debated nature of the Vrancea slab, its coupling with the overlying crust, and its potential for triggering crustal earthquakes. We use the nearest-neighbour distance to estimate the correlation between pairs of earthquakes, considering the origin time, magnitude, b-value and fractal dimension of the observed seismicity with Mw ≥ 2.5 from the 1977–2023 period. With this approach, we find a small percentage of clustered seismicity (8%), suggesting that background seismicity dominates. We identified 12 conventional mainshock-dominated sequences and 17 swarms with relatively small (0.92) and large (1.73) b-values, respectively, that may reflect differences in stress or the presence of fluids in the crustal volume. The aftershock decays—p-values of 0.99 for the large-event clusters and 1.42 for the swarms—may reflect typical and, respectively, fast stress relaxations. Swarm clusters are predominantly localised within the crust, whereas conventional mainshock sequences lack foreshocks and prevail in the subcrustal domain, occasionally triggering aftershocks at shallower depths. This partitioning suggests higher heat flow and fluid-modulated seismicity in the crust, as opposed to brittle failure conditions, triggered by slab dynamics in the mantle, including abrupt stress release without preceding signals. The spread of aftershocks from subcrustal large mainshocks to shallower depths indicate a stress transfer process where the descending Vrancea slab influences seismic activity in the overlying crust. [ABSTRACT FROM AUTHOR]

The Northern Margin Fault of the Yanqing Basin (NMYB Fault) is an important active fault at the intersection of the Zhangjiakou–Bohai (Zhang-Bo) Belt and the Shanxi Belt in North China. The Yanqing Basin, controlled by the NMYB Fault, is rich in escaping gas from hot springs, and previous investigations have indicated that the Yanqing Basin is located in the peak area of upwelling deep fluids from the mantle source material within the Zhang-Bo Belt. Hence, the site is suitable for geochemical gas precursor observations; to facilitate this, five new fault soil gas continuous stations were built on different segments of the NMYB Fault to carry out observations of fault gas (H2 and CO2) concentrations. The five new stations were approximately 50–60 m deep in the bedrock to monitor the release of gas from the depths of the fault. This was the first time that such geochemical station arrays were deployed in the same fault zone at a high density and depth. The results of the deep-hole observations of fault gas within the Yanqing Fault zone show that the time series of the hydrogen (H2) escape gas concentration has a close relationship with recent seismic activities, reflecting different physical processes of YFBF fault activity. The H2 concentration at the observatory was more sensitive to the stress-loading response of the NMYB Fault system. [ABSTRACT FROM AUTHOR]

The study of the Earth's ionosphere is a topic that has increased in relevance over the past few decades. The ability to predict the ionosphere's behavior, as well as to mitigate the effects of its rapid changes, is a matter of primary importance in satellite communications, positioning, and navigation applications at present. Ionosphere perturbations can be produced by geomagnetic storms correlated with the solar activity or by earthquakes, volcanic activities, and so on. The monitoring of space weather is achieved through analyzing the Vertical Total Electron Content (VTEC) and its anomalies by means of time series, maps, and other derived parameters. In this study, we outline a strategy to estimate the VTEC in real-time, its rate of change, and the corresponding Signal-to-Noise Ratio (SNR) based on dual-frequency GNSS Doppler observations. We describe how to compute these parameters from GNSS data for a regional network using Adjusted Spherical Harmonic Analysis (ASHA) applied to a local model. The proposed method was tested to study ionospheric anomalies for two seismic events: the 2015 Nepal and 2023 Turkey earthquakes. In both cases, anomalies were detected in the maps of the differential VTEC (DTEC), differential VTEC rate, and SNR of the VTEC produced close to the earthquake zone. The robustness of the results is strongly related to the availability of a dense Ionosphere Pierce Point (IPP) cloud on the ionospheric layer and surrounding the studied area. At present, the distribution of Continuously Operating Reference Stations (CORSs) around the world is insufficiently dense and homogeneous in certain regions (e.g., the oceans). Robustness can be improved by increasing the number of CORSs and developing new models involving measurements over ocean surfaces. [ABSTRACT FROM AUTHOR]

This study conducts a comprehensive analysis of observations related to the ML6.2 Hualien earthquake that struck eastern Taiwan on 6 February 2018, focusing particularly on gamma-ray emissions and total electron content (TEC) as earthquake precursors. Prior research has shown that significant gamma-ray enhancements are frequently detected at the YMSG (Yangmingshan gamma-ray) station prior to major earthquakes in eastern and northeastern Taiwan, suggesting that gamma-ray anomalies may serve as reliable indicators for identifying seismic precursors in this area. Our findings reveal a significant rise in gamma-ray emissions at the YMSG station from 19 January to 4 February 2018, which corresponds to a precursor period of approximately 18 days before the Hualien earthquake. Positive and negative TEC anomalies were observed in Taiwan on 20–21 January and 5 February, respectively, and may be considered as ionospheric precursors to the earthquake. Additionally, deep-learning techniques applied to TEC data facilitate the detection of ionospheric precursors associated with the Hualien earthquake, enabling forecasts of an approaching seismic event. Collectively, these observations indicate that all identified anomalies are regarded as short-term precursors, explicable through the theoretical framework of lithosphere–ionosphere coupling (LIC). [ABSTRACT FROM AUTHOR]

Egypt is fortunate to be less prone to natural disasters compared to other parts of the world. However, the seismic activity is low to moderate. Therefore, this relative stability is a positive factor for preserving the archeological sites. This cultural heritage is a major source of national income. Consequently, there is a strong interest from the state to preserve these sites from any probable natural hazards, especially the earthquakes. In the current study, the seismic hazard assessment has been conducted for south of Egypt, in particular at eight pharaonic temples' sites, utilizing the probabilistic seismic hazard approach within a logic-tree framework. Peak ground acceleration (PGA) and spectral acceleration (SA) values on rock site conditions have been estimated according to NEHRP site classification. The obtained seismic hazard maps show that Kalabsha, Abu Dabbab and Gulf of Suez seismic zones control the distribution of the ground-motion parameters. In addition, the uniform hazard spectra have been estimated to display that, the temple of Abu Simble is located away from Kalabsha seismic active zone, where the expected PGA and SA values at different return periods is relatively low in comparison with the other temples. Moreover, the ground-motion levels are also deaggregated at the temples' sites and the results indicate that, the distance to the seismic sources which mostly contributes to the seismic hazard is almost controlled by the nearby seismic sources. Therefore, the obtained results could serve as starting point to evaluate and mitigate the seismic risk at those precious historic sites. [ABSTRACT FROM AUTHOR]

The study presents the results of geoelectric research for seismic risk assessment on the example of the Kozlodui nuclear power plant in Bulgaria. The image of the geoelectric structure in the study area was obtained using one-dimensional inverse electrical resistivity modeling of the full five-component magnetotelluric data and quasi-three-dimensional inverse conductivity modeling of the geomagnetic responses recorded during the summer 2021 field campaign. According to the presented results, the geoelectrically anomalous structure is divided into two levels. The near-surface anomalous structure in the immediate reach of human geotechnical activity corresponds to the electrically conductive sedimentary fill. The mid-crustal layer is coincident with the low seismic velocity zone at the brittle and ductile crust interface, revealed in previous studies. The presented results imply that the geological environment is not affected by large faults capable of transmitting seismic energy from tectonically active areas, however, in further studies, attention should be paid to the strike-slip fault systems adjacent to the study area. [ABSTRACT FROM AUTHOR]

Background: Probabilistic Seismic Hazard Assessment (PSHA) is a leading methodology for determining key ground motion parameters such as Peak Ground Acceleration (PGA) and spectral acceleration (SA), essential for structural design. This approach uses extensive earthquake data, typically spanning over a century, leveraging frequency and magnitude statistics. However, long-term ground shaking probabilities may not always be accurately captured by traditional data-driven methods. To address these limitations, this study develops a PSHA map for Northern Chile using both seismic and GNSS (Global Navigation Satellite System) data. A curated homogeneous earthquake catalog, based on the advanced seismic moment magnitude scale Mwg(Das Magnitude Scale), replaces the traditional Mw scale to ensure superior accuracy, particularly for intermediate and smaller earthquakes. Results: Using the earthquake catalog, seismicity parameters 'a' and 'b' from the Gutenberg-Richter relationship were derived. Seismogenic modeling and Ground Motion Models (GMMs) were applied to estimate ground motion probabilities for a 475-year return period. Additionally, a PSHA map was constructed using GNSS strain rates, translating velocity-derived strain rates into seismic moment rates and ground shaking probabilities for seismic source zones. Comparative analyses revealed higher PGA values from GNSS strain data compared to seismic catalog data. GNSS strain data proved invaluable for refining seismic segmentation in Northern Chile, enhancing the precision of PSHA calculations. Conclusions: A PSHA map for Northern Chile, synthesizing seismic catalog data and GNSS strain rates using a Logic Tree-based algorithm, has been developed for a 475-year return period. This map provides a critical tool for generating seismic hazard assessments aligned with building codes and emergency planning protocols. By integrating GNSS strain rates and seismic data, this study advances the reliability and accuracy of long-term ground shaking predictions. [ABSTRACT FROM AUTHOR]

Many practical disaster reports are published daily worldwide in various forms, including after-action reports, response plans, impact assessments, and resiliency plans. These reports serve as vital resources, allowing future generations to learn from past events and better mitigate and prepare for future disasters. However, this extensive practical literature often has limited impact on research and practice due to challenges in synthesizing and analyzing the reports. In this study, we 1) present a corpus of practical reports for text mining and 2) introduce an approach to extract insights from the corpus using select text mining tools. We validate the approach through a case study examining practical reports on the preparedness of the U.S. Pacific Northwest for a magnitude 9 Cascadia Subduction Zone earthquake, which has the potential to disrupt lifeline infrastructures for months. To explore opportunities and challenges associated with text mining of practical disaster reports, we conducted a brief survey of potential user groups. The case study illustrates the types of insights that our approach can extract from a corpus. Notably, it reveals potential differences in priorities between Washington and Oregon state-level emergency management, uncovers latent sentiments expressed within the reports, and identifies inconsistent vocabulary across the field. Survey results highlight that while simple tools may yield insights that are primarily interpretable by experienced professionals, more advanced tools utilizing large language models, such as Generative Pre-trained Transformer (GPT), offer more accessible insights, albeit with known risk associated with current artificial intelligence technologies. To ensure reproducibility, all supporting data and code are made publicly available (DOI: 10.17603/ds2-9s7w-9694). [ABSTRACT FROM AUTHOR]

Utilizing statistical tests to evaluate earthquake forecasting models is crucial to improve forecasting strategies for seismic hazard assessment. We develop a novel evaluation method for alarm-based earthquake forecast, taking into account the magnitude of seismic energy and the impact area of earthquakes, instead of using solely seismic event number and epicentre locations in conventional approaches. First, we derive a scale law of Seismic Area by statistically analysing coseismal maps of past M  ≥ 7.0 earthquakes. Second, we proportionally allocate Seismic Moment to surrounding cells based on corresponding seismic area within each cell (SASM-test). Compared to the Molchan test which is conventionally applied for models that forecast the epicentre location, our proposed SASM-test can be applied to the evaluation of forecasting models that focus on the whole earthquake rupture (source area). Third, we apply the SASM-test method to the time-independent probabilistic earthquake forecasting model for the southeastern Tibetan Plateau (RELM-TibetSE) and compare it with other evaluation methods. The retrospective testing shows that the SASM-test demonstrate relatively higher sensitivity, enabling to detect subtle differences between similar models that conventional methods may overlook. Additionally, retrospective test results indicate that: (i) Earthquake forecasting models using Global Navigation Satellite System (GNSS) data performed better in forecasting the 'source area' than the 'epicentre location'; (ii) forecasting models based on principal strain rate outperformed the models based on maximum shear strain rate in forecasting both the epicentre location and the source area and (iii) incorporating spatially varying seismogenic layer thickness and rigidity into seismic forecasting models could improve their ability to forecast the 'source area' compared to using uniform seismogenic layer properties. The newly proposed SASM-test method can provide a more sensitive and comprehensive approach for the evaluation of earthquake forecasting models, contributing to the refinement of seismic hazard assessments. [ABSTRACT FROM AUTHOR]

We observed high-quality waves from a repeatable airgun seismic source recorded by a linear ultra-dense seismic array across the Xiliushui fault zone, one of the inactive faults in the Qilian Mountain, on the northeastern margin of the Tibetan Plateau, China. We used Snell's law of seismic ray propagation to determine a simplified ambient velocity model. Based on the flexible and precise spectral element method, we computed broadband synthetic seismograms for a shallow low-velocity fault zone (FZ) to model the direct P-wave travel time delay and incident angle of the wavefield near the FZ. The FZ extent range and boundaries were inverted by apparent travel time delays and amplification patterns across the fault. According to prior information on the properties of the direct P-waves, we could constrain the inverse modeling and conduct a grid search for the fault parameters. The velocity reduction between the FZ and host rock, along with the dip angle of the FZ, were also constrained by the P-wave travel time delay systematic analysis and incoming angle of the P-waves. We found that the Xiliushui fault has a 70~80 m-wide low-velocity fault damage zone in which the P-wave velocity is reduced to ~40% with respect to the host rock. The fault damage zone dips ~35°southwest and extends to ~165 m in depth. The repeatability and environment protection characteristics of the airgun seismic survey and the economic benefits of a limited number of instruments setting are prominent. [ABSTRACT FROM AUTHOR]

In order to improve and optimize the advance classification and prediction method of tunnel surrounding rock, a prediction method based on Tunnel Seismic Prediction (TSP) and Probabilistic Neural Network (PNN) is proposed. Based on the characteristics of science, maneuverability and representativeness, several factors that greatly affect rock mass classification are selected as evaluation indices based on analysis of numerous TSP data, establishing an advance classification index system for surrounding rock, and designing the "Advance classification and prediction system for surrounding rock" to predict the classification. Engineering application of Jinpingyan Tunnel of Chenglan Railway in high altitude and high intensity area of China is taken as a case study, and proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable, and compared with Back Propagation (BP) neural network prediction results, the results show that PNN has some advantages in predicting the calculation speed of surrounding rock classification, the ability to add samples and the classification accuracy in practical engineering applications. The PNN-TSP method can be further used for other tunnel engineering. [ABSTRACT FROM AUTHOR]

A Bottom Simulating Reflector (BSR) is a seismic feature closely related to marine gas hydrate as it is usually regarded as the seismic response of the base of the gas hydrate stability zone in seismic profiles. BSRs are widely distributed in the Makran accretionary wedge, and double BSRs are observed at some locations. Double BSRs usually appear on seismic profiles as two layers of BSRs located at distinct depths but with large lateral seismic amplitude variations. Based on the multi-channel seismic reflection data acquired over the Makran accretionary wedge, this work studies the origin of the double BSR in the Makran accretionary wedge and its association with fluid escape events. Our modeling suggests that double BSRs correspond to both the paleo-seafloor and modern seafloor caused by late sedimentary activities. Also, the residual paleo-BSR migrates upward due to the increase in local geothermal gradient caused by diapirs and gas chimney thermal fluids. [ABSTRACT FROM AUTHOR]

Indonesia is the country with the second highest earthquake intensity in the world because Indonesia is passed by the confluence of 3 tectonic plates, namely: the Indo-Australian Plate, the Eurasian Plate, and the Pacific Plate. Earthquakes occur due to the movement of tectonic plates that move freely and interact with each other. The impact of the earthquake includes: Tsunamis, collapsed buildings, fires, rock collapses, and ground cracks. The purpose of writing this study is to determine the intensity of earthquakes that occur on the island of Java using the K-Means Clustering method. The earthquake data used in this study uses magnitude, depth, and geographical location parameters obtained from existing data. The K-Means Clustering method is used to group earthquake data into several clusters based on their seismic characteristics. The result of this study is to identify seismic zones with similar earthquake intensity. The results of the cluster obtained, it was used to make data visualization of areas with high earthquake intensity using GeoMap. [ABSTRACT FROM AUTHOR]

The construction industry continually seeks to optimize the materials used in building projects to balance structural integrity with economic and environmental concerns. Particularly in urban high-rise construction and seismic zones, the choice of material can significantly affect the project's feasibility and safety. This study investigated the mechanical response of regular and lightweight concrete to bending stresses, which are critical factors in the structural design process. By comparing the strain–stress relationships, densities, and deformation capacities of these two varieties of concrete, this research aimed to clarify their fundamental differences. Lightweight concrete, with its lower density of 1800 kg/m3, offers noticeable weight reductions, thus presenting a viable solution for structures where reduced mass is beneficial, such as in areas with load-bearing limitations or for components that require ease of transportation and assembly. However, this study found that the reduction in weight is accompanied by lower compressive and flexural strength compared to normal concrete, which, with a density of 2400 kg/m3, exhibited greater mechanical strength and resilience under bending stresses. Stress–strain graphs generated from the experimental data illustrated both types of concrete's elastic and plastic deformation behaviors, highlighting the material's transition from elasticity to plasticity at specific stress points. This nuanced understanding of the materials' behaviors is vital for construction professionals as it equips them with the information necessary to make informed decisions on material selection, ensuring safety, sustainability, and cost-effectiveness in construction projects. [ABSTRACT FROM AUTHOR]

The use of tunnel boring machines (TBMs) in deep hard rock tunnels disrupts the original stress equilibrium of the rock mass, often resulting in the aggregation and release of a large amount of elastic strain energy, and even leading to rockburst. Under extremely high rockburst proneness conditions, advance stress release boreholes (ASRBs) deployed behind the TBM cutter head can be used to reduce stress concentration levels. However, there is a lack of scientific design methods for the parameters of the ASRB program for TBM tunnels, leading to poor stress release and difficulty in mitigating high-intensity rockburst hazards. This study proposes a parameter design method for ASRBs in the potential rockburst seismic source area of deeply buried hard rock TBM tunnels, including test scheme establishment methods, parameter selection methods, and parameter space relationship and evaluation index establishment methods. A deep tunnel in southwest China was used as an engineering case study to explore the effect of stress release and energy dissipation under different ASRB layout schemes. The results show that the sensitivity of the five important design parameters of ASRBs to the stress release effect is, in descending order, "aperture", "inclination", "included angle", "spacing", and "length". A parameter control law for ASRBs is proposed, which confirms their effectiveness in preventing, controlling, and reducing rockburst disasters in deep hard rock TBM tunnels. [ABSTRACT FROM AUTHOR]

Large strike-slip earthquakes are generally characterized by long surface rupture zones and relatively concentrated displacement distribution. The displacements on main seismogenic faults have been well studied and assessed by numerous empirical relations. Detailed mapping of the deformation zone of strike-slip earthquakes in the past decades indicates that distributed ruptures beyond the main faults have controlled the width of surface deformation zones and influenced the distribution of damages and earthquake-induced geological disasters. Therefore, the displacement hazard assessment from distributed surface rupture along strike-slip faults is urgent for disaster prevention and mitigation and the seismic safety of linear engineering. The Tibetan Plateau is marked by a series of strike-slip faults accompanied by lateral extrusion of material due to the Cenozoic collision of the Indian and Eurasian plates. In this study, we collected the surface rupture data of five strike-slip earthquakes in the Tibetan Plateau during the past decades, including the 1997 Mani ( M W 7.5), 2010 Yushu ( M W 6.9), 2014 Yutian ( M W 6.9), 2021 Maduo ( M W 7.4), and 2022 Menyuan ( M W 6.6) earthquakes. Then, we preprocess the original data to form the standardized dataset after removing the fractures due to non-tectonic factors such as landslides, gravity instability under seismic ground motion, and so on. Based on the standardized dataset, the surface rupture displacements generated by strike-slip faults are incorporated into a probabilistic displacement hazard analysis framework, and a probability model of the surface rupture displacement distribution is established for the Tibetan Plateau. This model estimates the probability per unit area of finding a distributed rupture that allows a displacement that exceeds a displacement threshold at a given distance from the principal fault. This study not only provides a framework for the probabilistic displacement hazard of distributed ruptures from strike-slip faults but also supports the seismic hazard assessment of linear engineering crossing strike-slip faults in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

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While fault creep-slip poses a risk to cross-fault tunnels in seismically active regions, intense ground shaking will impose more rigorous requirements on the safe functioning of the tunnel. Thus, the 100-year creep-slip dislocation of faults in the tunnel site area is calculated based on the Shantou Bay subsea tunnel, which crosses the active fault zone and is taken as the background and combining the actual engineering site characteristics and ground vibration parameters. A three-dimensional numerical calculation model of creep-slip-earthquake is established by taking into account the nonlinear plastic damage properties of the lining structure, and a study on the structural dynamic response of the tunnel to the initial damage caused by creep-slip of the fault is conducted. The results show that: (1)The tunnel has significant relative deformation near the fault fracture zone when it is only subjected to fault creep; the tensile and compressive impacts are more evident at the tunnel crown and invert, and the tunnel shows obvious shear state. (2) After the earthquake, the acceleration amplification phenomenon of the tunnel close to the fault zone becomes increasingly significant, with a maximum amplification factor of 3.0. (3) The horizontal deformation and arch waist strains of the tunnel following the ground shaking are significantly higher than the tunnel response under the single action of the superimposed ground slip . Maximum horizontal relative displacement is increased to 2. 90 cm, and the equivalent plastic strain is multiplied up to five times. (4)The tunnel under the fault creep-lip damage is confined at the fault plane, and the ground shaking action amplifies the damage, resulting in cumulative damages to the tunnel arch foot and shoulder. (5) With greater initial creep-slip dislocations causing more severe damage magnitudes and larger PGA causing a wider range of damage, the effect of ground shaking following creep-slip dislocation enhances the tunnel damage response. The tensile damage lining volume of the tunnel under creepslip-earthquake action can be enhanced by 224. 8% when compared to the tunnel without creep-slip damage. The study findings can serve as a design guide for cross-fault tunnel seismic performance in the Chinese high seismicity areas. [ABSTRACT FROM AUTHOR]

The ongoing expansion of high-speed railway systems in seismically active regions necessitates improved methods for evaluating the seismic resilience of the railway infrastructure. This study aimed to develop and establish a seismic performance indicator for coupled vehicle–track–tunnel systems to facilitate the assessment of safety under earthquake conditions. A refined finite element model was created, capturing the intricate dynamical interactions between a high-speed train, the track, and the tunnel, with a particular focus on the heterogeneity of the soil stratum. The model, synthesized through a joint simulation using HyperMesh and ABAQUS, was validated with theoretical solutions and experimental data, enhancing its predictive reliability of the system's seismic response. The research resulted in the innovation of a two-level seismic performance indicator, offering a quantitative tool for evaluating the integrity and safety of a high-speed railway tunnel during seismic events. Although the performance indicator has shown promise in initial validations, it is emphasized that continued verification and refinement are paramount for ensuring its adaptability across various seismic scenarios. The contribution of this research lies in providing a novel, rigorous approach for the seismic design evaluation, which is critical for advancing the safety standards of high-speed railway infrastructures. [ABSTRACT FROM AUTHOR]

The onshore wind turbines are gradually developing with the aim of large single‐unit capacity, large impeller diameter, and higher towers. The steel–concrete hybrid tubular tower structure is the mainstream structure of high‐hub towers, whose lower part is a concrete tower tube and the upper part a steel tower tube. Also, there is no doubt that more and more wind turbines will work in harsh environments and seismic hazard zones. Based on the abovementioned two points, it is necessary to mitigate the dynamic responses of onshore wind turbines to ensure the safety of these structures. This paper studied the base‐isolated method, story‐isolation method, and three types of tuned mass dampers damping method: single tuned mass dampers (STMDs), multiple tuned mass dampers (MTMDs), and distributed‐tuned mass dampers (D‐MTMDs), to explore the response characteristics of the steel–concrete hybrid tubular tower under seismic loads. The results show that the base‐isolated structure can greatly reduce the bending moment and shear response of the upper steel tower tube, while the story‐isolated structure has a very good effect on reducing the structural displacement response. In the three tuned mass dampers damping method, D‐MTMDs have stable and effective control capacity, compared with STMD and MTMDs. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) signals from a seismogenic zone a few weeks to a few days before an earthquake are considered as a promising attribute in earthquake precursory studies. EM perturbations, termed as the coseismic electromagnetic perturbations, also occur within the source zone at the onset of an earthquake and at recording sites during the passage of seismic waves. In the present study, we have analyzed the coseismic electromagnetic perturbations of the M 6.4 Nepal earthquake of 2023-11-03 and its main aftershock (M 5.6) of 2023-11-06, recorded at eight long-period magnetotelluric (LMT) sites installed in profile mode in the Ganga Basin about 150 to 250 km south-west of the earthquake epicenter. The time series were detrended, bandpass filtered, and rotated in the radial and transverse directions using back-azimuth. These time series mimic seismograms and show EM inductions corresponding to the arrival of the P, S and surface waves. Amplification of the surface wave at sites in the middle sector of the profile covering the Sharda depression having thick sedimentary succession and decrease in the amplitude at the southernmost site at the edge of the depression highlight the role of geological heterogeneities in controlling the EM induction. The presence of two very low amplitude consistent peaks at most sites, spread over a profile length of about 120 km, preceding the earthquake by 70 s and 43 s, respectively, is enigmatic. These signals arrive at most sites almost simultaneously and have peak-to-peak amplitude in the range of -0.07 to + 0.11 µV/m and −0.04 to + 0.07 µV/m, respectively, at fourth site. This is probably the first reporting of such preseismic electromagnetic signals in EM time series. We infer that these signals are possibly linked to the fast propagating EM waves generated during the final stage of the earthquake source zone preparation just before the initiation of the rupture. These signals need to be explored in the future for understanding of the causative physical processes. The results also reveal on average about 5 times reduction in the amplitude of the surface wave-induced electric fields with the drop in the earthquake magnitude from 6.4 to 5.6. [ABSTRACT FROM AUTHOR]

Primarily due to the scarce direct field evidence along a same fault, understanding the relationship between the pre‐existing off‐fault damage and coseismic slip distribution remains challenging. This study offers the first field‐based quantitative assessments of fault damage zones along the surface rupture generated by the 2008 Mw 7.9 Wenchuan earthquake in China over eight profiles with 254 outcrops. The width and mean tectonic fracture intensity of the damage zones exhibit pronounced variations along the fault strike. We introduce the damage index as a proxy to quantify the extent of pre‐existing damage. We find a statistically significant anti‐correlation between the damage index and coseismic on‐fault slip. We thus infer that pre‐existing off‐fault damage plays a significant role in dissipating rupture energy, thereby reducing coseismic on‐fault slip. This study provides a natural case for linking the long‐term fault zone evolution and the short‐term earthquake rupture dynamics. Plain Language Summary: Large earthquakes can cause significant surface ruptures, which often spatially coincide with severe seismic disasters. Therefore, understanding where large coseismic slip occurs is crucial for mitigating hazards. Off‐fault damage is an indispensable component of fault zone structure, and its impact on seismic behavior has been widely emphasized. However, unlike coseismic off‐fault damage, pre‐existing off‐fault damage cannot be easily observed through remote sensing. Investigating pre‐existing off‐fault damage and its influence on coseismic on‐fault slip is challenging yet essential for comprehending earthquake processes. To address this gap, we conducted a detailed field investigation along the surface rupture of the 2008 Mw 7.9 Wenchuan earthquake, China, characterizing the along‐strike distribution of fault damage zone. Comparing the extent of pre‐existing fault damage with the coseismic on‐fault slip profiles revealed an inverse relationship: a higher extent of pre‐existing off‐fault damage leads to smaller coseismic on‐fault slip. We propose that the dissipation of seismic energy occurring within densely fractured damage zones provides a possible explanation for this phenomenon. Our findings establish critical connections between long‐term fault zone evolution and short‐term earthquake rupture dynamics. From a disaster reduction perspective, identifying off‐fault damage along major active faults before future earthquakes may enhance fault displacement hazard assessments. Key Points: Detailed measurements of the pre‐existing off‐fault damage along the surface ruptures associated with the 2008 Mw 7.9 Wenchuan EarthquakeWe provide compelling evidence that a higher extent of pre‐existing off‐fault damage leads to smaller coseismic on‐fault slipWe discuss the seismic energy dissipation hypothesis for the mechanism of pre‐existing off‐fault damage impeding coseismic on‐fault slip [ABSTRACT FROM AUTHOR]

This paper examines areas of seismic activity in Southern Siberia. It is shown that the potential earthquake source (PES) zone model created for the general seismic zoning does not fully correspond to the data on the seismic activity of the region. For seismic stations at and near hydroelectric dams, a study of seismograms of large earthquakes from different epicentral zones of natural seismicity, as well as records of the largest man-made earthquakes in the region, has been carried out. Attention is paid to platform earthquakes in the areas of hydroelectric power stations. Current power spectra are studied, which show the level of influence of signals against the background of industrial noise and microseisms, and the frequency composition and duration of seismic vibrations of dams during different earthquakes is determined. This work is the first step towards assessing the impacts of earthquakes from the most active epicentral zones on hydroelectric power stations in Siberia, taking into account the real characteristics of the signals. The level of seismic effect of industrial explosions in the region is considered. The research is aimed at clarifying and improving seismic zoning in the areas where hydropower structures are located in Southern Siberia. [ABSTRACT FROM AUTHOR]

Magnitude prediction is a key focus in earthquake science research, and using machine learning models to analyze seismic data, identify pre-seismic anomalies, and improve prediction accuracy is of great scientific and practical significance. Taking the southern part of China's North–South Seismic Belt (20° N~30° N, 96° E~106° E), where strong earthquakes frequently occur, as an example, we used the sliding time window method to calculate 11 seismicity indicators from the earthquake catalog data as the characteristic parameters of the training model, and compared six machine learning models, including the random forest (RF) and long short-term memory (LSTM) models, to select the best-performing LSTM model for predicting the maximum magnitude of an earthquake in the study area in the coming year. The experimental results show that the LSTM model performs exceptionally well in predicting earthquakes of magnitude 5 < ML ≤ 6 within the time window of the test set, with a prediction success rate of 85%. Additionally, the study explores how different time windows, spatial locations, and parameter choices affect model performance. It found that longer time windows and key seismicity parameters, such as the b-value and the square root of total seismic energy, are crucial for improving prediction accuracy. Finally, we propose a magnitude interval-based assessment method to better predict the actual impacts that different magnitudes may cause. This method demonstrates the LSTM model's potential in predicting moderate to strong earthquakes and offers new approaches for earthquake early warning and disaster mitigation. [ABSTRACT FROM AUTHOR]