Seismic Deformation Research Articles

Effect of geometry on the natural frequency and seismic response characteristics of slopes subjected to pulse-like ground motions

Near-fault regions are particularly vulnerable to seismic-induced landslides due to the intense energy pulses in near-fault ground motions (NFGMs). These pulses, shaped by terrain geometry and material properties, significantly influence seismic response and slope stability. This study investigates the impact of slope geometry on natural frequency and seismic response characteristics under both pulse-like ground motions (PLGMs) and non-pulse ground motions (non-PGMs). The results show that increasing slope height lowers natural frequency, making the slope more susceptible to resonance with seismic waves, thus amplifying ground motion and increasing instability. Similarly, steeper slopes also reduces the natural frequency, heightening instability by up to 0.17%. PLGMs generate seismic responses approximately 7% stronger than those induced by non-PLGMs. Furthermore, as the frequency of PLGMs rises, so does their destructive potential. Material analysis reveals that Rock Class A has a natural frequency 68% higher than Rock Class D, making it significantly resistant to seismic deformation. These insights are essential for designing more resilient slopes in seismic-prone regions.

Seismic Deformation Analysis of Precast Concrete Pipe Hybrid Based on 3D LiDAR and Unmanned Aerial Vehicle Photogrammetry

Seismic Deformation Analysis of Precast Concrete Pipe Hybrid Based on 3D LiDAR and Unmanned Aerial Vehicle Photogrammetry

Correlating the seismic acceleration of reinforced concrete moment-resisting-frames with structural and earthquake characteristics

Nonstructural components (NSCs) are elements within the building unrelated to the lateral load-carrying system. Failure of NSCs during earthquakes can result in casualties, significant economic losses, disabled critical infrastructures, and loss of building functionality. The NSCs can be categorized into two primary groups: deformation-sensitive and acceleration-sensitive. Thanks to well-established seismic design guidelines and standards, buildings may suffer minor seismic deformations – resulting in lesser damage to deformation-sensitive components. However, planning under the peak floor response or peak floor acceleration (PFA) is getting much less attention – exposing the acceleration-sensitive components to greater risk. This manuscript develops equations for moment-resisting reinforced concrete frames (MRRCFs) that estimate the total floor acceleration. The data is gathered based on 984 inelastic response simulations, elaborated to create an idealized equation based on the earthquake characteristics. The developed equation offers engineers a quantitative approach to understanding the inertial forces applied to the NSCs within the building during earthquakes, allowing them to plan for potential risks due to earthquakes.

Geological and hydrogeological drivers of seismic deformation in L’Aquila, Italy: insights from InSAR analysis

Historical and recent earthquakes have struck the city of L'Aquila, located in the axial zone of the Central Apennines, Italy, causing severe damage to the historic centre. Recent studies have shown that higher intensity of damage to buildings in L’Aquila downtown, both in the case of the 2009 earthquake (Mw: 6.29) and the 1703 earthquake (Mw: 6.7), is associated with higher post-seismic subsidence rates, detected through A-DInSAR maps, in the time range 2010–2021. This finding suggests the existence of geological factors that drive deformation (and building damage). The availability of long time series of InSAR data acquired from the Cosmo-SkyMed and Sentinel-1 missions, has enabled us to analyze the relationships between ground deformations and geological, hydrogeological, and geomorphological factors that may affect them. The correlation analysis between predisposing factors and SAR deformation has highlighted an increase in subsidence strongly conditioned by the outcropping lithology, showing how compositional variations within lithology can significantly influence ground deformations. Furthermore, hydrogeology has been recognized as playing an important role in determining deformation processes: the water table depth locally influences long-term subsidence, while seasonal fluctuations in the water table may be responsible for secondary areal variations in ground deformations.

Deformation of solid earth by surface pressure: equivalence between Ben-Menahem and Singh’s formula and Sorrells’ formula

SUMMARY Atmospheric pressure changes on Earth’s surface can deform the solid Earth. Sorrells derived analytical formulae for displacement in a homogeneous, elastic half-space, generated by a moving surface pressure source with speed $c$. Ben-Menahem and Singh derived formulae when an atmospheric P wave impinges on Earth’s surface. For a P wave with an incident angle close to the grazing angle, which essentially meant a slow apparent velocity $c_a$ in comparison to P- ($\alpha ^{\prime }$) and S-wave velocities ($\beta ^{\prime }$) in the Earth ($c_a \ll \beta ^{\prime } \lt \alpha ^{\prime }$), they showed that their formulae for solid-Earth deformations become identical with Sorrells’ formulae if $c_a$ is replaced by $c$. But this agreement was only for the asymptotic cases ($c_a \ll \beta ^{\prime }$). The first point of this paper is that the agreement of the two solutions extends to non-asymptotic cases, or when $c_a /\beta ^{\prime }$ is not small. The second point is that the angle of incidence in Ben-Menahem and Singh’s problem does not have to be the grazing angle. As long as the incident angle exceeds the critical angle of refraction from the P wave in the atmosphere to the S wave in the solid Earth, the formulae for Ben-Menahem and Singh’s solution become identical to Sorrell’s formulae. The third point is that this solution has two different domains depending on the speed $c$ (or $c_a$) on the surface. When $c/\beta ^{\prime }$ is small, deformations consist of the evanescent waves. When $c$ approaches Rayleigh-wave phase velocity, the driven oscillation in the solid Earth turns into a free oscillation due to resonance and dominates the wavefield. The non-asymptotic analytical solutions may be useful for the initial modelling of seismic deformations by fast-moving sources, such as those generated by shock waves from meteoroids and volcanic eruptions because the condition $c / \beta ^{\prime } \ll 1$ may be violated for such fast-moving sources.

A ductile seismic design strategy for the cross-aisle direction of racking systems

Due to their lightness and simple connectivity, steel racking systems are typically considered as “low-dissipative” structures, which is reflected in the modern seismic codes by the absence of capacity design and the adoption of low behaviour factors. This limited capability of stress redistribution significantly increases the vulnerability of racks under beyond-design seismic hazards and raises the demand for more resilient designs. Along these lines, the proposed Plastic Ovalization Strategy (POS) attempts to increase the ductility of the individual upright frames comprising the cross-aisle direction of racks, and at the same time to preserve their low-cost and easy-to-assemble nature. This is achieved by tasking the bearing failure mechanism of the diagonal bolt hole to absorb seismic deformations, while capacity design is employed to keep the rest of the structure in the elastic zone. Following a detailed discussion on the motives and basic principles of the strategy, two high-rise racking systems are designed twice by professional engineers, once using standard approaches and then by additionally employing the proposed POS rules. Finally, the two design solutions are compared by conducting a comprehensive seismic assessment, which employs a phenomenological macro-model comprising elastic elements and nonlinear springs to simulate the bearing failure mechanism.

The strain demand of reinforced concrete bridge columns under seismic loading

The steel in reinforced concrete (RC) members that form plastic hinges must possess sufficient strain capacity to dissipate seismic deformation demands. Unfortunately, there is limited information on the seismic strain demands of bridge column plastic hinges. Instead, designers rely on a perception of cyclic strain capacity that is an approximate rule of thumb. A standard methodology needs to be established for quantifying the strain demand on these structural members as a function of the expected seismic hazard. To develop this methodology, 1944 columns were analyzed with nonlinear time-history analyses (NLTHAs) using ground motions from a range of earthquakes. This study evaluates the strain demand on RC bridge columns by defining the relationship between the strain demand and earthquake intensity. The results of the model are defined in terms of the peak tensile strain of the reinforcing bar, [Formula: see text]. The earthquake intensity with the highest correlation to the [Formula: see text] was determined to be the elastic spectral displacement at the optimal period ([Formula: see text]), which is defined as 75% of the effective period. The relationship between [Formula: see text] and [Formula: see text] can be used to predict the strain demand for an RC bridge column at a given geographic location. Results are presented as a probability density function (PDF), representing strain demand, compared to a PDF of the column capacity. The intersection of the capacity curve and demand curve represents the maximum acceptable strain given as a function of [Formula: see text]. This methodology can help understand the demand placed on a structural system given a region’s seismicity.

Seismic Deformation Analysis of the 28th September 2018 Palu Earthquake (7.5 Mw) Using InaCORS Station Data and Okada Model

This study employs the Okada Method to analyze the horizontal seismic deformation of the Palu earthquake on September 28, 2018, with a magnitude of 7.5 Mw. Data from InaCORS stations (WATP, CPRE, CPAL, TOBP, and CMLI) strategically positioned near the earthquake epicenter were processed using Gfortran software, and deformation was mapped using GMT software. The analysis focuses on the 100 Days of Year (DOY) period from August 6 to November 28, 2018. Results indicate that during the co-seismic phase (DOY 272), InaCORS stations experienced deformations ranging from 477.130 mm to 7.7852 mm. The magnitude of deformation varied based on station proximity to the epicenter, with the largest displacement observed at TOBP and the smallest at CPRE. Station movements were divergent, with northern stations shifting northward and southern stations moving southward. Subsurface slip reached 1449.23 mm, affecting an area measuring 145 km by 76 km at a depth of 8 km, dip of 65˚, strike of 351˚, and rake of -46˚. These findings contribute valuable insights into the seismic impact on the Earth's crust, aiding seismic hazard assessments in the region

DEFORMATION INTERACTION OF STRONG EARTHQUAKES OF 2010–2016 IN THE ZONE OF INFLUENCE OF THE HIKURANGA SUPERPLUME (NEW ZEALAND) ACCORDING TO GPS OBSERVATIONS

Between 2010 and 2016, a series of 11 strong M>6 earthquakes occurred in New Zealand. In the area covering the epicentral zones of these seismic events, the spatiotemporal characteristics of movements and deformations of the Earth’s crust were obtained based on the processing of continuous satellite GPS observations at 64 points of the geodetic network. Using these data, we have studied the evolution of horizontal movements and deformations in order to reveal the possible relationship between the observed deformational and seismic processes. Analysis has been made on the total shear deformation, since the main tectonic structures of the region are faults with a shear mechanism of displacement of their sides. The presence of a giant mantle superplume in the area was the reason for the study of the behavior of horizontal dilatation deformation, and horizontal and vertical crustal motions. Based on the obtained digital deformation models, there were created kinematic visualizations, which are synoptic animations providing direct observations of the seismic deformation process and their heuristic analysis. The study revealed that a series of the strongest earthquakes may be interconnected by a long-term single deformation process, which is caused by the occurrence of an anomalous total shear deformation. The general maximum of shear deformation, dilatation deformation, and horizontal and vertical displacements are concentrated in the center of mantle superplume activity. Prior to strong seismic events, there occur zones of deficit (minimum) displacements of the Earth’s crust in the area of future epicenters, which is of research interest in terms of predicting their locations.

Seismic fragility analysis of isolated bridges considering landslide-induced differential settlements

The structural safety of bridges and viaducts can be affected by the combination of different hazardous sources. This paper presents a study on the seismic fragility of continuous-deck bridges isolated through elastomeric bearings subjected to ground settlements induced by slow-moving landslides. In the investigated bridge typology, the relative differential displacement of bridge substructure components can involve significant strains of the bearing devices reducing their seismic deformation capacity and determining the increase of bridge fragility. Based on observations on a real case-study bridge, a parametric analysis is carried out to investigate the sensitivity of bridge fragility considering several realistic landslide-induced differential settlement scenarios and variable characteristics of the elastomeric bearings. Seismic fragility curves considering specific settlement scenarios are computed and compared to the undeformed condition to estimate the influence on fragility curves. Results show that a significant increase in fragility is registered for settlement scenarios inducing localized settlements of substructure components and for high-damping nonlinear seismic response.

Seismic Deformation Response Analysis of Shallow Buried Section at the Entrance and Exit of River Crossing Tunnel

Ensuring the safety of tunnel structures in unique underwater environments is of paramount importance. This study focuses on the entrance section of a river-crossing tunnel, characterized by shallow burial depths with significant variations. The tunnel structure faces challenges related to structural weakening, and its deformation response exhibits specific characteristics under seismic loads. Numerical simulation software was employed to model and calculate the deformation response of the shallowly buried entrance section under seismic load conditions, assessing the impact of changes in tunnel structural strength and burial depth. The results reveal the following key findings: (1) As the tunnel structure weakens, structures of varying strengths primarily experience vertical deformation under seismic loads, followed by horizontal deformation. Furthermore, as the tunnel structure’s strength decreases, it exhibits an increasing trend in deformation. Routine maintenance should prioritize locations where the tunnel structure weakens, implementing timely reinforcement measures to ensure adequate load-bearing capacity. (2) Considering the influence of tunnel structural burial depth, lateral deformation values rank in descending order from largest to smallest, including the tunnel bottom, middle carriageway, middle of the tunnel, and tunnel vault, while the overall lateral deformation of the tunnel is not significant, it decreases as the structural burial depth increases. (3) In relation to tunnel structural burial depth, vertical deformation values generally exceed horizontal deformation values. Sections with the highest to lowest deformation values are the tunnel bottom, middle lane of the tunnel, middle of the tunnel, and position of the tunnel vault. With increasing burial depth, the vertical deformation values decrease at a slower rate than horizontal deformation. The tunnel structure demonstrates a higher sensitivity of lateral deformation to changes in burial depth factors.

Deformation behavior of rectangular underground structures in liquefiable deposits correlated to ground motion intensity measures

Rectangular underground structures in liquefiable deposits are susceptible to larger deformation during earthquake events. The intensity of earthquake motions, as one of the critical factors that would induce large deformation of underground structures in liquefiable deposits, however, was not received enough recognitions. In this paper, nonlinear dynamic analyses with a probabilistic seismic demand model (PSDM) were conducted for a two-dimensional liquefied soil-structure system, considering a variable thickness of liquefiable layer below the structure. The nonlinear soil behavior was simulated by the nonlinear constitutive model PDMY02. The constitutive parameters of saturated sand were calibrated by a slope model in the centrifuge test from LEAP-2017. Interstory drift ratio (IDR) and uplift ratio (UR) of underground structures were selected as engineering demand parameters (EDP). There were totally 18 recorded earthquake motions and 8 intensity measures (IMs) included for the PSDM. Numerical results show that the uplift behavior of underground structures is more sensitive to the variable thickness of liquefiable deposits compared to the horizontal drift of the structure. According to the performance of correlation, efficiency, practicality and proficiency, the velocity-related IMs are more appropriate than the acceleration-related IMs for the evaluation of seismic deformation behavior of underground structures. The deformation response as well as the adaptability of velocity-related IMs are further discussed and evaluated by considering more general cases including different buried depths and height-width ratios for rectangular underground structures.

Co- and Pre-Seismic Crustal Deformations Related to Large Earthquakes Between Years of 2009 and 2023 Using Continuous CORS-TR GNSS Observations in the Anatolian Diagonal (Turkey)

Synoptic animations of internal displacements and deformations of the earth's crust were obtained based on the results of continuous GNSS observations in Eastern Anatolia from 2009 to 2023. The spatiotemporal patterns of the seismic deformation process in connection with the tectonics of the region have been identified. It is shown that dilatation and total shear strains evolve in concert with the migration of the strongest earthquakes Elazig, Elazig-Malatya and devastate Karamanmaraş series. Two years before the occurrence of the devastating earthquakes of 2023, a deficit of internal displacements of GNSS stations developed in the area of their epicenters. The conducted research suggests that the strongest events of 2009-2023 are connected by a unitary seismic deformation process. The most important action in this case is the SW movement of the Anatolian block as monolithic element. In the development of movements and deformations, a flow of increasing stresses is observed in the direction from Karliova Triple Junction to the SW to the area of the strongest seismic events on 02.2023. It originates east of the Karliova Triple Junction where the Arabian Plate encounters an obstacle. The role of mantle flows in the seismic process is assessed

Cyclic behavior of dual-steel beam-to-column welded flange-bolted web connections

Cyclic loading tests on dual-steel beam-to-column welded flange-bolted web connections were conducted to quantify their moment resistance, plastic deformation and energy dissipation capacities. The test program consisted of five one-sided connection specimens, where Q355 grade beams and Q690 grade columns were used, to study the effects of beam-to-column welded flange connection details and panel zone shear strength on the connection seismic performance. Two types of welded connection details were considered; one was the traditional complete-joint-penetration (CJP) welded connections by use of backing bars, and the other type was those with the bottom backing bar further reinforced by a fillet weld. Three column web thicknesses were designed to arrive at strong, intermediate and weak panel zones, respectively. It was found that the CJP weld with the backing bar reinforced only under the bottom beam flange produced satisfactory performance and accommodated plastic rotations larger than 0.03 rad, while a maximum plastic rotation of 0.04 rad could be developed in the high-strength steel panel zone before fracture occurred. These results evidenced that those dual-steel connections could still sustain high seismic deformation demands.

Seismic Deformations at the Ancient Settlement of Raevskoe and Seismotectonics of the Northwestern Caucasus

Seismic Deformations at the Ancient Settlement of Raevskoe and Seismotectonics of the Northwestern Caucasus

Seismic Deformations in Khudoyar Khan Palace, Kokand, Fergana Valley

Seismic Deformations in Khudoyar Khan Palace, Kokand, Fergana Valley

Response Displacement Method for Seismic Calculation of Subway Station Complex Structure of TOD Mode

The TOD mode with rail transit stations as the center has become an important direction of future central city construction. However, at present, there is still a lack of simplified calculation methods for the seismic design of a subway station complex structure of TOD mode. Based on the load-structure model of the classic response displacement method and the seismic deformation characteristics of the underground complex structure, an improved response displacement method for seismic calculation of the subway station complex structure considering the influence of the upper frame structure was proposed in this paper. Then, based on the actual engineering case, the applicability of the improved reaction displacement method was verified through investigating the influencing factors such as seismic wave type, ground motion intensity, building position, structure form, structure stiffness, and stratum stiffness. Furthermore, a series of numerical simulation experiments were conducted to verify the simplified method and further evaluate its computational accuracy. The result shows that the error in calculating the internal force and deformation response of a station complex structure by using the improved reaction displacement method can be controlled at about 10%. The improved response deformation method is proved to be a highly practical pseudo-static method.

Focal mechanism of a Late Triassic large magnitude earthquake along the Longmen Shan fault belt, eastern Tibetan Plateau

Stress states near active fault zones are key to understand their seismogenic setting, geodynamic evolution and future seismic activity. The Longmen Shan Fault Belt (LSFB) is a prominent fault zone that has had a long history of activity and major recent earthquakes in the eastern Tibetan Plateau. However, we have no records of major events prior to the 2008 Wenchuan earthquake, and this hinders progress in understanding both the past and future seismicity of the LSFB. A Late Triassic pseudotachylyte, recently discovered and dated, provides an opportunity to compare modern stress states with those acting ca. 230 Ma ago. Here we use a new paleoseismological approach, based on the magnetic fabric of the fault rocks, to determine the focal mechanism of Late Triassic seismic events, each recorded in pseudotachylyte veins at the Bajiaomiao outcrop. The anisotropy of magnetic susceptibility (AMS) of pseudotachylytes and cataclasites arises from the shape-preferred orientation of coseismic neoformed magnetite and monoclinic pyrrhotite, whereas that of protocataclasite arises mainly from the crystallographic preferred orientation of inherited clastic magnetite. The AMS of fault rocks shows well-defined magnetic foliation and lineation. The pseudotachylyte generation vein formed along the plane where seismic slip took place, while the AMS obliquity with respect to this plane indicates seismic slip with ∼248° trend and 38° dip. This result is consistent with the attitude of macroscopically visible subhorizontal striations on the pseudotachylyte plane itself. The consistent asymmetry of multiple injection veins with respect to the pseudotachylyte generation vein, along with the asymmetry of the AMS fabric, shows that seismic deformation resulted from left-lateral, strike-slip motion. This study provides the oldest example, to date, of focal mechanism determination using the AMS method. The kinematics of the Late Triassic event departs from that of the 2008 Wenchuan earthquake thrust motion. Yet, with a displacement estimated between ∼4.4 and 17.4 m, the magnitude of the Late Triassic event was likely Mw 7.5–7.9.

Effects of near-fault and far-fault ground motions on nonlinear dynamic response and seismic damage of masonry structures

This study explores the seismic behavior of masonry buildings in close proximity to a fault rupture as compared to those located farther away. It takes into account the distinctive features of near-fault ground motions, such as forward directivity and the fling effect, which have the potential to cause significant earthquake-related damage. The study employs a dataset comprising 100 earthquake records, which represent both near-fault and far-fault ground motions and conducts an analysis of nineteen masonry buildings with varying typologies. Analytical models for each of these buildings are constructed using experimental data concerning the quality of masonry materials. Nonlinear static and dynamic analyses are carried out to evaluate the buildings' capacity to withstand seismic deformations and the extent of damage incurred. The findings indicate that near-fault ground motions exert a more significant influence on the dynamic response and result in greater damage to masonry structures when compared to far-fault ground motions.

Experimental-analytical investigation of accelerated bridge construction concrete columns with self-centering Fe-SMA bars subjected to near-fault ground motions

Excessive seismic damage and residual deformation in bridge piers can result in time-consuming post-earthquake repair and replacement, which will adversely affect the recovery and seismic resilience of the transportation infrastructure. Seismic damage or permanent deformation in bridges can be minimized using advanced materials and novel technologies, of which shape memory alloy (SMA) has gained substantial momentum. The goal of this study is to investigate the feasibility of using unbonded iron-based shape memory alloy (Fe-SMA) bars as self-centering elements in accelerated bridge construction (ABC) piers to reduce residual seismic deformation. Shake table testing is performed on a one-third-scale bridge column specimen subjected to near-fault ground motions. A numerical model of the test specimen is developed in OpenSees, and the “pre-test” analysis results are compared with the experimental measurements. Acceptable correlations are observed between the simulated and measured residual drifts, accelerations, forces, and hysteretic responses. Furthermore, the test results are compared to that of a similar conventional cast-in-place RC column without self-centering elements. The maximum residual drift ratio in the tested Fe-SMA column specimen is found to be much smaller than the conventional column specimen highlighting the potential benefits of the proposed design.