Seismic Stress Research Articles

Dynamic Response Analysis of Dowel-Slot Grouting Assembly Station under earthquake action

In order to study the seismic performance of Dowel-Slot Grouting Assembly Station, the displacement and stress changes of the station and the cast-in-place station under horizontal, vertical and horizontal-vertical coupled earthquakes were compared by the finite element numerical simulation method based on a subway station in Changchun. The results indicate that the two stations have the same stress concentration position and the same weak point under different seismic actions, and both meet the aseismic requirements. Compared with the traditional cast-in-place station, the assembly station has obvious advantages in vertical seismic performance, but the horizontal seismic ability is relatively weak, and the difference of the displacement Angle between layers is 20%~60%. Compared with the difference of 46.43% in the maximum seismic stress and 28.51% in the vertical seismic time, the difference of 58.02% in the coupled seismic action shows that the stress concentration is more obvious. It provides reference for further optimization of assembly station.

ST-elevation myocardial infarction incidence in a high-risk seismic zone.

Earthquakes are unpredictable natural events that can elicit acute physiological responses, potentially triggering cardiovascular events. This study investigates the association between seismic activity and ST-elevation myocardial infarction (STEMI) admissions in a tertiary care hospital in an earthquake-prone region over 19years. We analyzed STEMI admissions at a tertiary center in Mexico City from October 2005 to August 2024. Earthquakes with a magnitude ≥6.0 and geographic relevance to Mexico were identified using the USGS database. Admission rates were compared for ±7days surrounding each earthquake and control periods derived from the same date in the previous year, adjusted for overlaps and seismic events. Poisson regression analyses were used to compare admission rates. Among 9611 STEMI patients, 904 admissions occurred near earthquake periods, with 863 during controls. Post-earthquake admissions rose significantly on the day earthquake (day 0) with an incidence rate ratio (IRR)=1.49 (95% CI 1.17-1.89, P=0.001), and in the post-quake (+1 to +7days) IRR=1.19 (95% CI 1.03-1.36, P=0.015) compared to the pre-quake (-7 to -1days) period. Notably, admissions on days +1 and+2 (IRR=1.54 [95% CI 1.11-2.14] and 1.58 [95% CI 1.07-2.34]) showed a significant increase compared to controls. Elevated systolic blood pressure was observed post-quake, while demographics, severity, and mortality showed no significant differences. Our findings suggest a significant association between earthquake events and increased STEMI admissions within the days following an earthquake in a high-seismic area. Compared to pre-earthquake and control periods, the observed rise in post-earthquake admissions indicates that seismic stress may contribute to STEMI events.

Evaluation of seismic stress changes in the northern part of the Zagros in Iran

Evaluation of seismic stress changes in the northern part of the Zagros in Iran

Integrative analysis of the Aachen geothermal system (Germany) with an interdisciplinary conceptual model

The comprehension of geothermal systems involves the efficient integration of geological, geophysical and geochemical tools that are crucial in unraveling the distinct features inherent in geothermal reservoirs. We provide a first approach to comprehending the geologically complex geothermal system in the Aachen area, which has been known for its natural thermal spring occurrences since Roman times. Through a comprehensive analysis involving geochemical interpretation of water samples, a review of 2D seismic profiles, stress analysis, and surface geology, a dynamic model has been built, which serves as a conceptual framework providing a clearer understanding of the system. The model characterizes a non-magmatic, detachment fault-controlled convective thermal system, wherein the reservoir exhibits mixed properties of the mainly Devonian carbonate rocks. NW–SE directed fault lines play a pivotal role in fluid transport, enabling the ascent of thermal waters without the need for additional energy. We additionally conducted magnetotelluric (MT) surveys and analyzed apparent resistivity and impedance values obtained through forward modeling, along with an assessment of noise levels. These findings contribute to evaluating the potential use of MT methods in further evaluating the study area and for geothermal energy exploration in general.

Single pile response to uplift load: Computational model and analysis

Uplift loading is imparted on piles when subjected to overturning moment on the supporting structures, seismic stresses or hydrostatic pressures. Although several experimental and theoretical studies are available on piles subjected to uplift load, a complete analysis on pile-soil interactive performance under such loading is limited. The authors have developed a numerical model based on boundary element technique considering hyperbolic stress-strain response of soil, elastic-perfectly plastic pile and interface slippage condition. The model is validated by comparison of numerical results with available laboratory and field test data wherein acceptable agreement is obtained. The model is utilized to carry out extensive parametric studies on uplift behavior of single piles in clay and sand including load-displacement responses, profiles for interface shear stress and uplift displacement, critical depths, etc. The load-displacement responses were found as initially linear, then hyperbolic. With depth, the magnitude of interface shear stress increased, while the pile displacements decreased. The L/D ratio influenced uplift pile capacity as well as limit-state displacement. Furthermore, a set of design curves are developed to ascertain the safety and serviceability criteria of uplift piles in clay and sand. From the entire work, a series of important conclusions are drawn.

Exploring Similarities and Differences in Water Level Response to Earthquakes in Two Neighboring Wells Using Numerical Simulation

The seismic effect of well water level is complex and variable, and even if both wells are located in an area with similar tectonic and hydrogeological conditions, they exhibit slightly varying response characteristics to the same earthquake. Wells BB and RC, located about 100 km apart in the southwest of the Huayingshan fault zone in the Sichuan and Chongqing regions, exhibited obvious similarities and differences in their co-seismically response and sustained recovery characteristics during the Wenchuan Ms8.0 earthquake. Based on the dislocation theory and fluid–solid coupling theory, this study developed the seismic stress–strain model and the response model of pore pressure to seismic stress using Coulomb 3.3 and COMSOL 6.3, respectively. Simulation findings indicate that both BB and RC are located in the expansion zone, where their water levels show a co-seismic step-down. The amplitudes of BB and RC water levels are 83 cm and 81 cm, which are approximately 10 cm smaller than the actual values. The recovery times are 60 d for BB and 3 h for RC, closely resembling the actual values. Furthermore, the numerical results from different scenarios show that the recovery time of pore pressure is reduced by several times when the permeability of the confining layer overlying the observed aquifer increases by one order of magnitude or the thickness decreases, and this change is more sensitive to the permeability. It is clear that the confining condition has an important impact in the response time of sustained changes in well water levels, which may also help to explain the variations in the characteristics of sustained changes in wells BB and RC.

Ridgecrest Aftershock Stress Drops from P- and S-Wave Spectral Decomposition

ABSTRACT Seismic moment and stress drop are crucial for understanding earthquake rupture processes, but their estimates often have large uncertainties for small earthquakes. Stress drop is typically inferred from an earthquake’s source spectrum based on theoretical models, but poorly constrained path corrections and other modeling assumptions limit the accuracy of stress-drop estimates. Here, we compute stress drops using both P and S waves for the 2019 Ridgecrest earthquake sequence, compare their estimates, and evaluate the associated uncertainties. We use spectral decomposition and apply the analysis to both types of waves for the same set of earthquakes, adjusting some S-wave parameter choices to obtain overall consistency with our P-wave results. Our approach fixes the corner frequency of small calibration earthquakes to reduce scatter in the estimated source parameters of the larger earthquakes. We find that assuming a lower high-frequency fall-off rate for S waves yields more consistent absolute stress-drop estimates between P and S waves. Our stress-drop estimates appear to increase slightly with magnitude for earthquakes with magnitudes >∼3.4. Furthermore, we find that the stress-drop estimates using both types of data exhibit coherent spatial variations. Earthquakes near the Coso geothermal field tend to have lower stress drops, and earthquakes near the M 7.1 hypocenter have higher stress-drop estimates. This spatial pattern is consistently observed in both the P- and S-wave results. We find no strong correlation between our stress-drop estimates and the M 7.1 Ridgecrest earthquake slip distribution, suggesting a heterogeneous stress environment for the Ridgecrest fault system.

Seismic impact of mainshock-aftershock sequences on underground caverns: A case study of dynamic response

At present, the seismic research of underground caverns mainly focuses on the mainshock effect, but ignores the aftershock hazard, and fails to fully consider that the cumulative damage after multiple earthquakes will reduce safety reserves of underground caverns. Therefore, based on incremental dynamic analysis method, this study selects real seismic records to construct single mainshock-aftershock sequence. The seismic response of underground cavern under single mainshock and single mainshock-aftershock is compared, and the sensitivity dominant index and seismic stress path of underground caverns under mainshock-aftershock is also expounded. Taking the Yingliangbao (YLB) hydropower caverns which experienced Luding MS6.8 earthquake as the research background. The mainshock-aftershock sequences with multiple aftershocks are constructed based on the real earthquake records in YLB area. The nonlinear dynamic response (NDR) of underground cavern under multiple mainshock-aftershock sequences is revealed. The results indicate that the residual displacement is more suitable as an evaluation index of the NDR of underground caverns under mainshock-aftershock than the peak displacement and yield zone volume. The residual displacement of underground cavern is related to the number of earthquake excitations, and multiple aftershock excitations will further increase the residual displacement of surrounding rock. The results can enrich the stability analysis and seismic design of underground caverns under mainshock-aftershock.

Co- and post-seismic deformation of the 2022 Menyuan Mw6.6 earthquake from InSAR and GPS observations

SUMMARY This study combines InSAR (Interferometric Synthetic Aperture Radar) and GPS (Global Positioning System) data to examine the coseismic slip and post-seismic deformation of the 2022 Menyuan Mw 6.6 earthquake, shedding light on the fault structure, slip distribution and rheology of the northeastern Tibetan Plateau. InSAR coseismic deformation revealed fault dip angle of 82° for the Lenglongling fault and 84° for the Tuolaishan fault. The optimal coseismic slip model, derived from InSAR, GPS and near-field pixel-offset data, indicates a maximum slip of 3.3 m, concentrated in the upper 3 km of the fault. We propose a three-step procedure to comprehensively invert the post-seismic deformation, accounting for both afterslip and viscoelastic relaxation, constrained by the InSAR and GPS observations. The optimal afterslip model indicates a cumulative afterslip of 9 cm over two years, primarily concentrated in the deeper sections of the coseismic slip zone. Incorporating viscoelastic relaxation improved the spatial distribution of the afterslip on the Tuolaishan fault. The afterslip released a seismic moment of 1.96 × 10¹⁸ N·m, accounting for approximately 15 per cent of the coseismic moment release. The viscosity of the lower crust in the region was estimated to range from 1.5 to 5 × 1018 Pa·s, with an optimal value of 2 × 10¹⁸ Pa·s. As the distance from the epicentre increased, viscoelastic relaxation became the dominant post-seismic mechanism, contributing up to 80 per cent of the deformation observed at the QHGC and GSMI stations. Additionally, the earthquake increased Coulomb stress on the ‘Tianzhu Seismic Gap’ and nearby faults, raising seismic hazard in the region. These findings highlight the importance of simultaneously considering both afterslip and viscoelastic relaxation mechanisms in post-seismic deformation analysis, and accounting for post-seismic effects when evaluating seismic stress changes.

Research on the Source Parameters and Scaling Relations of Earthquakes in Qinba Mountain and Its Adjacent Area

Abstract In this paper, the source parameters were determined for 123 small to moderate size earthquakes (1.2 ≤ ML ≤ 4.5) occurred during 1997-2013 in Qinba Mountain and its adjacent area by using the digital seismic data recorded in Shaanxi seismic network. The scaling relations between seismic moment, stress drop, seismic radiated energy with seismic magnitude are determined, the relations between scaled energy Eg/M0 and seismic moment are analyzed. The results show that the seismic stress drop in this area approximately increases with the increase of seismic moment, but the seismic stress drop is generally low. The Zúñiga parameter ε is generally less than 1, indicating partial stress drop mechanism in the region and may be the activity of low strength mature faults. The seismic scaled energy in this area is relatively small, which may be the results of high dynamic friction force or insufficient estimation of seismic radiation energy.

Analysis of the dynamic response and damage characteristic for the tunnel under near-field blasts and far-field earthquakes

The dynamic response and failure characteristics of tunnels vary significantly under various dynamic disturbances. These characteristics are crucial for assessing structural stability and designing effective support for surrounding rock. In this study, the theoretical solution for the dynamic stress concentration factor (DSCF) of a circular tunnel subjected to cylindrical and plane P-waves was derived using the wave function expansion method. The existing equivalent blast stress wave was optimized and the Ricker wavelet was introduced to represent the seismic stress waves. By combining Fourier transform and Duhamel’s integral, the transient response of the underground tunnel under near-field blasts and far-field earthquakes was determined in both the frequency and time domains. The theoretical results were validated by comparing them with those obtained from numerical simulations using ANSYS LS-DYNA software. Numerical simulations were conducted to further investigate the damage characteristics of the underground tunnel and evaluate the effect of initial stress on structural failure under both types of disturbances. The theoretical and numerical simulation results indicated that the differences in the dynamic response and damage characteristics of the underground tunnel were primarily due to the curvature of the stress waves and transient load waveform. The locations of the maximum DSCF values differed between near-field blasts and far-field earthquakes, whereas the minimum DSCF values occurred at the same positions. Without initial stress, the blast stress waves caused spalling damage to the rock mass on the wave-facing side. Shear failure occurred near the areas with maximum DSCF values, and tensile failure occurred near the areas with minimum DSCF values. In contrast, damage occurred only near the areas with maximum DSCF values under seismic stress waves. Furthermore, the initial stress exacerbated spalling and shear damage while suppressing tensile failure. Hence, the blast stress waves no longer induced tensile failure on the tunnel sidewalls under initial stress.

A coupled displacement-pressure model for elastic waves induce fluid flow in mature sandstone reservoirs

Elastic (seismic) wave stimulation is considered one of the unconventional enhanced oil recovery (EOR) methods. Increasing water quantity in the high permeability layer of a mature oil reservoir is highly challenging and can significantly decrease the ultimate recovery due to the reservoir heterogeneity. Using seismic waves can be considered low-cost, environmentally friendly, and illuminates the entire reservoir size compared to conventional EOR methods. A numerical model is developed by extending the Quintal approach for seismic attenuation due to wave-induced fluid flow (WIFF) to incorporate capillary pressure in partially saturated porous media and shift undrained boundary conditions to exclude external flow stress for drained boundary conditions. Therefore, the fluid distribution due to the capillary effect makes the developed finite element method (FEM) u-p model more widely applicable for oil recovery in mature reservoirs. A two-layer partially saturated media was subjected to compressive seismic stress at low frequency (3 Hz). The results indicated that the vertical displacement gradients of the bottom and upper layers decline with excitation time for both fully and partially saturated media. On the other hand, partially saturated pore pressure gradients of both the upper and bottom layers have higher amplitudes with excitation time than fully saturated pore pressure gradients due to the influence of capillar pressure. The cumulative crossflow oil volume for 180 days of continuous stimulation was 1176 bbl, 1032 bbl, and 648 bbl in low permeability layers: 200 md, 100 md, and 50 md, respectively. Therefore, the developed model has the potential for field-scale EOR applications. The study also suggests coupling elastic EOR with CO2 flooding to recover more oil due to increasing fluid mobility and relative permeability to oil in low-permeability reservoirs or tight formations.

Numerical simulation of seismic stress evolution in the Lajishan Fault zone on the northeastern margin of the Qinghai-Xizang Plateau

To analyze the triggering relationship of historical earthquakes to the 2023 Jishishan earthquake and estimate the seismic risk in the adjacent region after the earthquake, we calculate the evolution process of seismic stress generated by 11 earthquakes with MS ≥ 6.0 and 1 earthquake with MS5.7 near the source in the past 100 years. The results show that before the 2023 Jishishan earthquake, the entire Lajishan Northern Edge Fault zone was under the stress shadow generated by the 12 earthquakes. The stress reduction at the 2023 Jishishan earthquake epicenter was approximately 15.1 kPa, and the contribution of this stress shadow mainly comes from the 1920 MS8.5 Haiyuan earthquake. The coseismic stress drop at the epicenter was around −292.1 kPa, and the maximum stress drop for the 2023 Jishishan earthquake was around −346.2 kPa. The Jishishan earthquake increased the stress of the two seismic gaps in the Lajishan Northern Edge Fault by 14.7 kPa and 59.7 kPa respectively, the stress on the Lajishan Southern Edge Fault zone increased by 10.9 kPa, and the stress on the east section of Xunhua Nanshan Fault increased by 11.1 kPa. These stress increments potentially elevate the seismic hazard along these fault zones. In the future earthquake prevention and disaster reduction, attention should be paid to the seismic risk of these fault zones.

Seismic Assessment of Masonry Minarets under Different Earthquakes

Minarets are tall and slender structures and form important elements of mosques. Most historical minarets are constructed with masonry (brick or stone units), while modern minarets typically use reinforced concrete. Recent earthquakes have shown that the majority of these structures are highly susceptible to seismic excitation leading to a range of structural damage, from minor cracking to complete collapse. In this paper, the seismic response of a representative masonry minaret was investigated using acceleration records of the 1999 Kocaeli, 2003 Bingöl and 2011 Van earthquakes. All acceleration records were scaled according to the location of the minaret. For this purpose, a representative masonry minaret that is thought to have been built in the city's central part of Elazığ, Turkey was chosen. After the seismic analysis, displacement and stress values obtained on the minaret were presented. It was seen that the displacements were increased along the height of the minaret. Also, the maximum and minimum stress values were obtained between the cylindrical body and transition segment of the minaret in accordance with the damage zones in the past earthquakes.

Tidally modulated seismic velocity changes observed using submarine dark fiber and the virtual-source method

Natural cyclical stress perturbations, including wet and solid earth tides, coupled with repeatable seismic monitoring approaches, provide a tool for understanding the elastic properties of rocks at depth. Ocean tides, in particular, perturb the overburden and pore pressure, affecting hydraulic and elastic rock properties. The recent emergence of distributed acoustic sensing (DAS) and seismology using existing dark telecom fiber offers an unprecedented opportunity to instrument the seas and oceans with seismic monitoring networks of large aperture, fine spatial resolution, and broadband sensitivity. We use a submarine dark-fiber array to methodologically assess whether the changes in seafloor seismic velocities are modulated by ocean tidal loading. Considering oceanic ambient noise (AN) in the frequency range between 1 and 5 Hz, we find it possible to retrieve reliable surface-wave estimates using relatively short time windows (approximately 60 min). Next, using the power of linear arrays to capture AN energy from the stationary-phase zones and AN processing techniques commonly used in DAS applications for subsurface monitoring in urban settings, we introduce a methodological approach to turn each segment of dark fiber into a short-offset monitoring array (2 km), providing redundant, hourly, surface-wave estimates. Using four days of AN data recorded by the Monterey Accelerated Research System (MARS) 20 km section offshore cable, we generate the virtual-source gathers for 10 segments spanning the whole MARS cable. We then use virtual-source data from one segment to estimate the hourly velocity changes that are then quantitatively compared with the tidal data. The results suggest that changes in seafloor seismic velocities are likely modulated by tidal height, even in regions without large tidal excursions. This advance demonstrates a new application of submarine telecom fibers for monitoring the seismic stress response of near-seafloor sediments.

Hydro‐Mechanical Characterization of a Fractured Aquifer Using Groundwater Level Tidal Analysis: Effect of Pore Pressure and Seismic Dynamic Shear Stresses on Permeability Variations

AbstractGroundwater level tidal analysis is a powerful technique to monitor aquifer's permeability and hence its change over time. Earthquakes are known to affect aquifer's properties, in their vicinity through static stress changes but also further away through dynamic stresses. Most often changes are in the form of permeability increases, but sometimes decreases; the changes can be either permanent or transient. These observations are relatively well documented but the physical processes behind these changes are not well understood. By combining solid‐earth and barometric tidal groundwater level responses in a borehole in a coherent poroelastic theoretical framework, and a bi‐layer hydrogeological model, we recover a 15 years‐long time series evolution of aquifer transmissivity and shear modulus. This study showcases the full potential of the tidal analysis method, coupling pore pressure diffusion and rock deformation, at the frontier of hydrogeology and rock physics. This unprecedented measurement of permeability and shear modulus evolution by tidal analysis reveals, during interseismic period, high sensitivity of this shallow aquifer to effective stress, and thus to pore pressure. Thanks to additional finite element simulation of seismic wave propagation, we explore the different mechanisms affecting permeability and shear modulus in the studied fractured andesite aquifer. This study confirms the predominant role of seismic dynamic stresses, and more precisely of dynamic shear stresses, in the change of permeability following an earthquake.

Evaluation of Shear Wall Configurations in RCC Structures for Seismic and Wind Load Resistance

RCC structures are extensively used due to their versatility and durability. The major problem in RCC structures is the dynamic forces like seismic and wind loads. Lateral forces generate stresses that cannot be resisted by a conventional RCC building without special design provisions. Shear walls are vertical elements of RCC structures, which resist lateral loads and increase the stability, strength, and safety of buildings. The review of roles, configurations, and benefits of shear walls in resisting seismic and wind-induced stresses relates their ability to check lateral displacement, minimize torsion, and maximize the dissipation of energy. There are various kinds of shear walls which include concrete variants and masonry variants and other configurations, namely flanged walls, rectangular coupled walls. In this context, discussions of challenges in their implementation, including architectural constraints and construction inaccuracies, are set alongside advancements in analytical and design techniques to optimize their performance. This review highlights the indispensable role of shear walls in ensuring compliance with modern building codes and standards while enhancing the resilience and longevity of RCC structures.

An investigation into dynamic behaviour of reconstituted and undisturbed fine-grained soil during triaxial and simple shear

This study aims to evaluate the factors controlling the sensitivity of fine-grained soils to seismic stresses and revise the criteria previously proposed by the authors to diagnose liquefaction. To this end, dynamic tests have been performed on artificial mixes as well as natural soils from a wide area of an earthquake devastated city (Adapazari) using two types of dynamic testing. Studies have led to findings suggesting that the gray area between susceptible and non-susceptible soils proposed by several investigators in the past can now be dispensed with. Although physical properties of fine-grained soil supply sufficient information for diagnosis, the dynamic simple shear test is found to be a convenient and rapid way to confirm the judgement. However, it has been seen that dynamic testing alone may not be the last word in the determination of liquefaction, and physical properties should also be addressed. Anomalies observed in test results are also discussed. Conclusions show significant differences from existing proposed criteria in the literature.

Seismic Response Prediction of Porcelain Transformer Bushing Using Hybrid Metaheuristic and Machine Learning Techniques: A Comparative Study

Although seismic response predictions are widely used for engineering structures, their applications in electrical equipment are rare. Overstressing at the bottom of the porcelain insulators during seismic events has made power transformer bushings in substations prone to failure. Thus, this paper proposed and compared six integrated machine learning (ML) models for seismic stress response predictions for porcelain transformer bushings using easily monitored acceleration responses. Metaheuristic algorithms such as particle swarm optimization were employed for architecture tuning. Prediction accuracies for stress response values and classifications were evaluated. Finally, shaking table tests and simulation analyses for a 1100 kV bushing were implemented to validate the accuracy of the six ML models. The results indicated that the proposed ML models can quickly forecast the maximum stress experienced by a porcelain bushing during earthquakes. Swarm intelligence evolutionary technologies could quickly and automatically aid in the retrofitting of architecture for the ML models. The K-nearest neighbor regression model had the best level of prediction accuracy among the six selected ML models for experimental and simulation validations. ML prediction models have clear benefits over frequently used seismic analytical techniques in terms of speed and accuracy for post-earthquake emergency relief in substations.

A sensitive system based on radon amplification at soil-air interface: Aiming to advance earthquake precursor research

Radon, a natural radioactive gas, serves as a valuable tracer in geophysical research and atmospheric science such as detecting stress induced signal in bedrock. However, the conventional radon monitoring methods often lack the sensitivity required to accurately capture such signals. This limitation, coupled with interference from meteorological effects, poses challenges in distinguishing genuine stress-induced signals. In this study, we propose a novel approach utilizing radon concentration gradients at the soil-air interface to enhance sensitivity and detect stress induced radon signals more effectively. Drawing from pressure diffusion models, we demonstrate how seismic stress accumulation in bedrock alters radon profiles in the sub-soil, providing insights into the mechanisms underlying stress-induced radon variations. Building upon this theoretical framework, we introduce the “Bhabha Radon Observatory for Seismic Application (BhaROSA)," a remote sensing, solar-powered radon observatory designed for widespread deployment and continuous unattended monitoring for big database generation. Field experiments comparing BhaROSA's performance to conventional soil probe techniques validate and confirm the superior sensitivity in line with theoretical predictions. This innovative approach holds promise for improving our understanding of stress dynamics in bedrock and has potential applications in various geophysical and atmospheric science such as earthquake precursory research, geo-genic radon potential and risk assessment. To progress, we propose international alliance and application of deep learning to a big database of precursor signals, which may lead to more informed conclusions on earthquake predictability-an enduring and unsolved challenge for humanity.