Search Results (135)

This study focuses on RCS frame structures and selects six different types of ground-motion intensity measures (IMs), including peak ground acceleration (PGA), spectral acceleration at the fundamental period Sa(T₁), the modified intensity measure S^* considering period elongation effects, IM₁₂ and IM₁₂₃ accounting for higher-mode effects, and Housner intensity (HI). Based on a set of near-fault pulse-like ground-motion records, a Bayesian seismic fragility analysis characterized by different IMs is conducted. This study reveals the influence of these IMs on the estimation of fragility parameters under three limit states—immediate occupancy (IO), life safety (LS), and collapse prevention (CP)—using both uniform non-informative priors and lognormal weakly informative priors. The results indicate that, in terms of the applicability of IMs across different limit states, all IMs exhibit highly stable fragility parameters in the elastic IO stage, where the results from maximum likelihood estimation (MLE), uniform priors, and lognormal priors are nearly identical, suggesting that sufficient sample information renders the influence of priors negligible. In contrast, in the CP stage, characterized by strong nonlinearity and collapse, the differences among IMs become most pronounced. HI consistently yields stable results across all methods with almost no variation. When the structure enters the CP stage with small samples and strong nonlinearity, the lognormal prior effectively promotes distribution convergence, suppresses over-dispersion, and corrects asymmetry, significantly improving the robustness of parameter estimation. Notably, different IMs exhibit varying sensitivity to Bayesian priors, among which S^* and HI are the least sensitive, demonstrating strong inherent stability and minimal dependence on prior constraints. Full article

Earthquakes may cause severe damage to engineering structures in the seismogenic fault zone. In near-fault regions, ground motions on the two sides of a fault exhibit significant asymmetry in terms of permanent displacement, velocity pulse, and dynamic displacement amplitude. Taking the Xianglu Mountain Tunnel in the southwest of China as the engineering object, this study designed scaled fault-crossing tunnel-surrounding rock test models and conducted a series of quasi-static and dynamic model tests using a dual-shaking table system with non-uniform ground motion input. The effects of three different earthquake action modes on the responses of tunnel engineering structures crossing seismogenic faults were investigated through five static and dynamic earthquake action modes. The test results indicate that considering only the dynamic effect of ground motion or only the static effect of permanent displacement due to fault dislocation will underestimate the seismic response and damage degree of the surrounding rock and tunnel structure. However, the contribution of dynamic effects of ground motion to tunnel failure is much smaller than that of static fault dislocation. The magnitude of permanent displacement from fault dislocation, the peak displacement of non-uniform ground motion time history, and the peak relative displacement are all important factors affecting the deformation of surrounding rock and the strain of tunnel structures. Traditional static analysis methods will lead to an underestimation of the damage risk of tunnel structures. Compared with the non-uniform earthquake action mode, the deformation within the fracture zone under the static action mode is underestimated by approximately 6.39%, and the peak tensile strain under the static action mode underestimates the damage risk by approximately 40%. Full article

The M_L4.9 Wang Nua earthquake on 20 February 2019 is the largest earthquake to occur in Lampang Province in the past four decades and identifies the potential seismic hazard of previously unmapped faults in northern Thailand. We reanalyzed this earthquake sequence using waveform-based matched-filter detection and double-difference relocation techniques. The enhanced catalog increases the number of small earthquakes by 2.5 times compared with the official record. It also reveals microearthquakes down to M_L–0.3, including a previously unreported foreshock sequence beginning approximately four hours before the mainshock. Relocated hypocenters define an 8 km long, near-vertical N-S striking rupture zone at depths of 0.7–10.6 km. The focal mechanism of the mainshock indicates right-lateral strike-slip motion (strike ~189°, dip ~77°, rake ~–150°), aligned with the kinematics of other extensions of the Phayao Fault Zone. These results indicate that the sequence occurred on a previously unrecognized fault segment. This highlights the importance of high-resolution seismic analysis for improving hazard assessment in regions with concealed fault systems. Full article

Fault-crossing ground motions, characterized by velocity pulses, permanent fault dis-placement, and non-uniform support excitation associated with fault rupture, may significantly affect the seismic performance of siphon bridges crossing active faults. This study investigates a long-span siphon arch bridge subjected to pulse-type fault-crossing ground motions. A unified stochastic ground motion model is developed by integrating nonstationary high-frequency components based on the evolutionary power spectrum with low-frequency pulse components represented by an improved Gabor wavelet, capturing forward directivity effects, permanent displacement, and differential support input at the two sides of the fault. A three-dimensional nonlinear finite element model is established in OpenSees using fiber-based beam–column elements, with hydrodynamic effects incorporated through the added mass method. Parametric analyses consider pulse phase angle (0–90°), amplitude (Mw 6.0–7.5), and frequency (0–1 Hz). Results indicate that structural responses decrease with increasing phase angle, with 0° being most unfavorable, high-lighting the dominant influence of permanent displacement. Resonance amplification occurs when pulse frequencies approach the fundamental modes of the pier (0.345 Hz) and deck (0.51 Hz), while the arch is particularly sensitive near 0.439 Hz. Water added mass reduces natural frequencies by 8–14% and significantly amplifies internal forces. These findings provide guidance for seismic design of fault-crossing siphon bridges. Full article

Transmission tower-line systems spanning active faults are simultaneously subjected to the “dual characteristic seismic actions” of permanent ground displacement (PGD) and spatially varying near-fault ground motions, rendering their failure mechanisms far more complex than those under conventional site-specific seismic actions. This paper investigates a 500 kV double-circuit “two-tower, three-line” coupled system by establishing a high-fidelity finite element model. An analytical framework is proposed, centered on indexing seismic action and structural response by key parameters: “Permanent Ground Displacement–Peak Differential Displacement–Velocity Pulse Period” (“PGD–Δmax–Tp”). By employing synthesized ground motions, the displacement time history is decomposed into three components—a velocity pulse, high-frequency background noise, and permanent displacement—thereby achieving a strict decoupling of these three control variables. Based on this methodology, three sets of controlled-variable scenarios were constructed to systematically reveal the independent influence of ground motion spectral characteristics, permanent displacement, and peak differential displacement on the system’s response. The research indicates that: spectral characteristics modulate the failure mode (the whiplash effect is triggered when the period ratio μ is approximately 1–2, whereas tower leg buckling occurs when μ ≫ 1); a threshold PGD value exists that triggers a shift in the structural force-resisting mechanism; and the peak differential displacement (Δmax) causes the system’s response to transition from being dominated by conductor slackening and unloading to being governed by inertia and P-Δ effects. The insights gained into the asymmetric response characteristics of towers on opposite sides of the fault provide a quantitative reference for the revision of seismic design codes for cross-fault power transmission projects. Full article

Near-fault earthquakes generate pulse-type ground motions that impose concentrated displacement demands on RC members, often leading to rapid degradation in stiffness and localized damage to negative-moment regions of T-beams. Although polymer-modified mortar (PMM) overlays with embedded reinforcement have demonstrated improved behavior under monotonic and cyclic loading, their response under seismic inputs with different characteristics remains insufficiently clarified. This study presents a parametric numerical investigation of RC T-beams strengthened with PMM overlays and embedded D13 and D16 steel bars and subjected to representative near- and far-field earthquake excitations. A three-dimensional nonlinear finite element model was developed and qualitatively validated against previously reported monotonic and reversed cyclic experimental results, with close agreement in the strength development and failure characteristics. The validated model was subsequently used in nonlinear time-history analyses. Under near-fault excitation, strengthening increased the peak load capacity by 52.40% (D13) and 73.30% (D16) relative to the control beam. For far-field motion, capacity gains of 53.77% and 65.85% were obtained, respectively. Near-fault input created pronounced localization in the compression zone, whereas far-field excitation resulted in more distributed cyclic deterioration. PMM strengthening substantially enhanced the flexural resistance and crack control, underscoring the importance of explicitly considering ground-motion type in performance-based seismic retrofit design. Full article

An integrated numerical method is proposed for analyzing the nonlinear seismic response of near-fault building clusters, comprising three algorithms: (1) a structural investigated lump algorithm for elastoplastic dynamic response of structure; (2) a connecting investigated lump algorithm for bidirectional wave propagation between the site and elastoplastic building clusters; (3) a geomedia investigated lump algorithm for seismic wave propagation with an improved viscoelastic constitutive model, which allows independent definition of P/S-wave quality factors to characterize geomedia attenuation. Validated for its capability in simulating site-city dynamic interaction problems via a shaking table test, the method is applied to study the seismic response of near-fault building clusters in Xichang City under a hypothetical M_w6.8 earthquake. It is shown that irrespective of whether shallow geological structures are considered, clusters (c2–c4) situated in rupture-forward surface area within ~1.5 km of the fault trace entered the elastoplastic stage, while others (c1, c5) remained elastic. Shallow geological structures may reverse locally hanging-wall/footwall effects of both near-fault structural seismic response and ground motion. A notable seismic-response characteristic of near-fault structures undergoing the elastoplastic stage is that the permanent structural motion displacement (PSMD) at the slab of a specific floor incorporates not only the non-zero permanent ground motion displacement (PGMD) but also the non-zero final structural residual displacement (FSRD) relative to the supporting ground. The developed method could provide support for seismic damage assessment, site selection, and structural optimization design of near-fault building clusters. Full article

Earthquake-induced landslides are a major hazard in mountainous regions, where complex topography and near-surface conditions jointly control ground-motion amplification and slope instability. In this context, ground-motion models used as triggering inputs for landslide analyses must accurately represent site effects in complex terrain. This study develops a geomorphometry-informed ground-motion model based on predictors derived from global remote sensing Digital Elevation Models (DEMs), conceived as a triggering component for earthquake-induced landslide applications. The model is based on the eXtreme Gradient Boosting (XGBoost) regression algorithm and predicts peak ground acceleration, peak ground velocity, and spectral accelerations by integrating seismic source parameters, finite-fault source-to-site metrics, and geomorphometric site proxies derived from global DEMs. The model is trained on an extended Italian strong-motion dataset comprising about 8300 recordings from 90 earthquakes with finite-fault rupture models and is evaluated using a strict leave-one-event-out validation scheme. Results show that finite-fault parameterization reduces prediction errors by about 11% compared to point-source formulations, while DEM-derived site proxies improve predictive performance by approximately 5% relative to V_S30 and 12% relative to the fundamental frequency f₀. Residual analysis yields inter-event variability of 0.19–0.22 and intra-event variability of 0.23–0.26. The proposed framework demonstrates how global remote sensing products provide value-added predictors for ground-motion triggering in complex terrain, suitable for integration with earthquake-induced landslide susceptibility models. Full article

Prior studies have shown that socio-economic and structural risks can be correlated with earthquake effects. The quantification of these effects was used to formulate robust disaster risk reduction (DRR) strategies and building codes. This is more pronounced in countries with complex tectonic settings, such as the Philippines, where strong-to-major earthquakes can occur. Here, we report the evaluation of deterministic ground shaking (GS) intensity measurements for Camarines Norte, the Philippines, with the objective of assessing and mapping the susceptibility of communities to intense ground motion. GS intensities and peak ground acceleration (PGA) were computed using the Rapid Earthquake Damage Assessment System (REDAS) software developed by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). The PGA was computed as a fraction of acceleration due to gravity, while GS used the PHIVOLCS Earthquake Intensity Scale (PEIS). Simulations were based on recorded earthquakes and mapped active faults near the province. Geographic information systems were used to stack and refine each simulation. Results showed that 13 earthquakes and 13 seismic source zones classified most of the province as PEIS VIII or higher, with the PGA maximum at 0.66 g. The results implied that the province is susceptible to very destructive to completely devastating ground shaking, and it is recommended to incorporate these results into DRR policymaking. Full article

Historical masonry minarets are highly vulnerable to seismic actions due to their slender geometry, limited tensile capacity, and material heterogeneity. However, their response to near-fault ground motions characterized by velocity pulses remains insufficiently explored. This study investigates the seismic response of the historical Tavanlı Mosque Minaret (1894, Trabzon, Türkiye) subjected to pulse-like (PL) and non-pulse-like (NPL) near-fault ground motions. A three-dimensional finite element model (FEM) was developed in ANSYS Workbench and systematically calibrated using empirical formulations to represent the current dynamic condition of the structure. Seismic performance was evaluated through linear dynamic analyses in terms of displacement demands, principal stress distribution, and drift-ratio-based performance levels. The results indicate that model calibration significantly modifies the dynamic characteristics, increasing the fundamental frequency from 0.734 Hz to 1.126 Hz and reducing displacement demands by approximately 35–76% across the considered records. Despite this improvement, PL ground motions consistently generate more critical deformation demands than NPL motions, frequently exceeding Collapse Prevention (CP) limits even when Peak Ground Acceleration (PGA) values are relatively low. A key finding is that seismic demand cannot be reliably predicted by peak intensity measures or pulse-period ratios ($T_p/T_1$) alone; rather, velocity-related parameters and pulse coherence govern the structural response. These results demonstrate that integrating empirical model calibration with pulse-sensitive seismic analysis is essential for reliable seismic assessment and conservation planning of slender historical masonry structures located in near-fault regions. The study offers a systematic framework that integrates model calibration and pulse-sensitive seismic analysis for evaluating the drift-controlled response of slender historical masonry minarets in near-fault regions. Full article

The Mw 6.4 Petrinja earthquake on 29 December 2020 ruptured the Petrinja-Pokupsko fault system in central Croatia, producing widespread coseismic deformation and subsequent postseismic processes. This study examines ground displacements in the Petrinja area from 2019 to 2022 using Sentinel-1 SAR data processed with SBAS time series analysis. Interferometric phase residuals were filtered using temporal coherence masking and RMS cut-off criteria to ensure high-quality displacement estimates. Line-of-sight (LOS) velocity fields were derived separately for ascending and descending tracks, combined into horizontal and vertical components, and rotated into a fault-parallel direction. Fault-parallel velocities were also extracted with pixel-wise coseismic offsets removed to isolate postseismic transients. Pre-event displacements are generally small and often within measurement uncertainties. However, because the 2019–2022 observation window includes the mainshock and concentrated early postseismic motion, robust estimation of long-term interseismic rates (millimeters per year) is not possible from this dataset. Such rates from independent regional GNSS measurements are therefore included solely for tectonic context and visual illustration. A clear surface displacement jump exceeding 20 cm was detected, with opposite signs in ascending and descending geometries, reflecting predominant right-lateral strike-slip motion. Following the removal of the coseismic jump, weighted profile analysis identifies residual transients of up to ±1.5 cm/yr near the fault, consistent with dominant shallow afterslip. Possible contributions from viscoelastic relaxation are noted, as such processes produce broader, longer-timescale deformation patterns that cannot be excluded without extended observations or forward modeling. These geodetic observations quantify the immediate postseismic deformation and provide constraints on near-fault slip patterns following the mainshock. Full article

The Tinjar–West Baram Fault in the southern South China Sea is a major NW-trending strike-slip fault that has remained tectonically active since the Oligocene. It forms a key structural boundary between the Zengmu, Beikang, and Nansha Trough basins. Multi-phase strike-slip movements have strongly controlled sediment provenance dispersal pathways, and reservoir development in the Zengmu Basin, yet the sedimentary response to these tectonic processes remains poorly understood. This study integrates 2D seismic profiles to analyze the fault geometry, kinematics, and impact on deep-water sedimentary systems. Results indicate that Oligocene right-lateral motion directed sediment supply from the southwest, mainly sourced from Kalimantan, forming fluvial–deltaic systems with depocenters in the southern basin. Since the Late Miocene, a transition to left-lateral motion reoriented sediment provenance toward the southeast, leading to delta-front complexes and northward migration of depocenters. Strike-slip activity deformation enhanced rock fragmentation and sediment supply, producing fan delta, fluvial, and shallow lacustrine facies near the fault. Associated uplift and subsidence induced relative sea-level fluctuations, resulting in alternating transgressive–regressive sequences. From the Late Eocene to Miocene, the basin evolved from a land–sea transitional system to a deltaic–carbonate complex controlled by the paleo-Sunda River. During the Pliocene–Quaternary, sedimentation was dominated by shallow-marine shelf and semi-deep-marine deposits. Fault-related fracturing significantly enhanced porosity and permeability, creating favorable conditions for hydrocarbon migration and entrapment in both sandstone and carbonate reservoirs. These findings demonstrate a strong coupling between strike-slip fault activity and sedimentary system evolution, providing important insights into sedimentary processes and hydrocarbon potential in strike-slip fault-bounded basins globally. Full article

This study selected a simplified water intake tower model, simplifying the physical structure into a cantilever model, and MATLAB software (R2010b) was used to develop a rapid seismic response analysis program for the structure. Thirty near-fault pulse and non-pulse ground motions were selected as the input ground motions for this analysis. Peak ground velocity (PGV) was used as the intensity parameter for the ground motions. The acceleration, cross-sectional rotation, and lateral curvature of the simplified water intake tower model were calculated for ground motions modulated with different PGA amplitudes. The acceleration, maximum shear force, and cross-sectional rotation of the simplified water intake tower model were also calculated for ground motions modulated with improved effective peak acceleration (IEPA) and improved effective peak velocity (IEPV). The study showed that the seismic response of the simplified water intake tower model for near-fault ground motions modulated with different intensities of PGV amplitude modulation was closer to the unmodulated response order. PGV as an intensity parameter did not affect the acceleration response amplification factor of the water intake tower and hoist chamber. The AC coefficient indicated that PGV was less suitable for pulse-type earthquake amplitude modulation than PGA. Compared with PGA amplitude modulation, IEPA amplitude modulation is more suitable for pulse-type seismic motion, while IEPV amplitude modulation has less impact on pulse-type seismic motion. Full article

This study investigates the selection and scaling of recorded strong ground motions in the time-domain spectral matching framework to realistically represent the seismic demands on the superstructure and secondary systems in the seismic design of complex facilities such as marine ports. The time-domain spectral matching method iteratively adjusts the original record in the time domain by adding wavelets with limited durations and specific period ranges to achieve compatibility with the specified target acceleration response spectrum. A site-specific probabilistic seismic hazard analysis (PSHA) was performed for a port facility in İskenderun Bay, an area affected by the 6 February 2023 earthquakes. Horizontal Ground-Motion Response Spectra (GMRS) were derived for different return periods. Based on the hazard deaggregation, recorded ground motions compatible with the seismotectonic context of the region and the site conditions were selected. These records were then processed using time-domain spectral matching (TDSM) to match their elastic response spectra with the target GMRS over specific period ranges. The method utilizes spectral matching in the time domain to improve the match with the target spectrum while preserving the phase information and non-stationary nature of the records. The results show that the mean spectral acceleration curves of the scaled records are highly consistent with the target GMRS over a wide range of periods and that near-fault pulse-like characteristics, when present, are reasonably preserved. These results confirm that time-domain spectral matching provides a reliable framework for the performance-based assessments of complex port infrastructures by achieving high compatibility with the target spectra while preserving the physical characteristics of the waveforms Full article

This review offers a comprehensive analysis of the mechanical behavior and evolving design strategies of bridge bearings subjected to vertical seismic loading. Existing studies underscored that intense vertical ground motions—particularly those with high peak accelerations and rich frequency content—can provoke separation and subsequent impact between girders and bearings. Such interactions are especially harmful due to the inherently limited tensile resistance of conventional bearing systems. To evaluate vertical seismic performance, two core parameters are emphasized: tensile capacity and controlled energy dissipation. In recent years, the concept of tensile-resistant seismic design has garnered growing interest. By integrating high-strength steel cables, shape memory alloys (SMA), and advanced elastomeric materials, researchers have developed novel mechanisms that enhance the vertical resilience of bearings. This review synthesizes current understanding of near-fault seismic phenomena, recent advancements in bearing technology, and prospective research directions, thereby offering theoretical insight for optimal bearing selection and design, and contributing to the refinement of relevant engineering codes and standards. Full article