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We have carried out historical and macroseismic studies of Khudoyar Khan Palace in Kokand (Fergana Valley, Uzbekistan). Inclinations of walls and colonnades, damaged upper parts of walls and minarets, and architectural oddities in the arcades of the outer facade of the eastern wall of the palace were revealed. We assume that the palace was largely built by the time of the Kokand earthquake of 1822–1823, and a strong seismic event severely damaged its solid buildings. This may explain the significant gap between the initial stage of construction and its final phase of 40 years. The epicentral zone of this earthquake was located southwest of the palace. The Kokand earthquake stopped construction and, while memory of the earthquake and its victims was strong, the unfinished and dilapidated palace stood without attention. Time passed, the generation changed, memory of the tragic event was obscured, and the new khan needed a headquarters. The unfinished palace was completed, but traces of the strong Kokand seismic event remained, visible even to the present. As for the major Chatkal earthquake of 1946, its dynamic impact in Kokand was apparently underestimated. The local intensity of seismic oscillations of Il = 5.5, of course, could not have tilted the well-built brick wall of the Palace Chancellery to the east. This requires oscillations with an intensity of at least Il ≥ 6.5. Additional studies of the macroseismic field during this earthquake in the Fergana Valley should be carried out. [ABSTRACT FROM AUTHOR]

The complexity in nonlinear behavior of torsional-irregular buildings in combination with uncertainty due to the natural randomness of earthquake records has been always a main challenge for buildings' seismic design. To find a solution to this challenge, three reinforced concrete (RC) building archetypes were designed and next developed into their nonlinear models. Nonlinear static (pushover) analyses were performed to calculate the capacity of the archetype models in all principal and non-principal directions while incremental dynamic analyses (IDAs) were conducted by applying 30 accelerograms from both near-field and far-field earthquakes. The IDA capacity curves, collapse fragility curves and log-normal cumulative distribution functions (CDFs) were established by including both the aleatory randomness and epistemic uncertainty. Despite previous studies wherein fragility curves were given by evaluating structures' collapse along structural reference axes or simply on x , y -axes, in this paper, possible building collapse on a critical non-principal direction (where maximum seismic response was observed) was simulated and its probability was accounted for developing IDA curves and log-normal CDFs. Accordingly, this issue was mirrored in computing available/acceptable collapse margin ratios (CMRs). In addition to the well-known outline used for calculating CMRs in the literature (that is based on estimation of collapse capacity in terms of earthquake intensity measure (IM)), the framework proposed here includes a new method for calculating the CMRs in terms of displacement-based drift, ductility, and damage. The superiority of the proposed method over the former is consistent with the buildings' design procedure that is governed by storey drift control rather than base-shear strength. Refined statistics of CMRs given by taking into account displacement-based responses illustrate the available CMRs exceed the acceptable CMRs, meaning that a satisfactory safety margin against collapse will be anticipated in the targeted building class if a suitable yielding mechanism with sufficient ductility is provided for seismic force-resisting system by applying seismic design provisions of the current codes. [ABSTRACT FROM AUTHOR]

Incremental dynamic analysis (IDA) is one of the widely used methods for structural assessment analysis and fragility curve development, given its unique capabilities in taking into account the aleatory uncertainties of earthquake records and its ability to provide a desirable statistical population of the system response. However, the strong dependence of the results on the number of selected records, the record selection process and scaling procedure, as well as the associated high computational costs are some of the obstacles, which limit the practicality of the IDA method especially in the case of large-scale structures. In the present study, an alternative approach called "Response Bounds" is proposed to estimate the expected range of structural responses under earthquakes with different intensity levels and to develop seismic fragility curves. To reduce computational costs and address the challenges associated with the record selection, a novel scenario-based Endurance Time (ET) analysis method is adopted. The good agreement between the fragility results of 5-, 10-, and 15-storey steel moment-resisting frames obtained by the proposed method and the IDA (less than 9% error) demonstrated the accuracy and reliability of the predicted results. The method could also estimate the mean loss ratio from fragility curves with less than 5% error in all cases. The proposed response-bound method can significantly reduce the computational costs of conventional seismic fragility assessment methods, and therefore can be used as an efficient tool for seismic reliability analysis in practical applications. [ABSTRACT FROM AUTHOR]

A series of earthquakes that struck Taiwan's southern Longitudinal Valley on September 17 and 18, 2022 severely damaged several buildings in Taitung and Hualien. The Chishang earthquake, which had a magnitude of ML 6.8 and a large foreshock with a magnitude of ML 6.6 the day before, was the mainshock in this sequence. The strongest intensity reported in the epicentral region during this earthquake sequence, which was 6 + , is the highest ever recorded since the Central Weather Bureau (CWB, renamed as the Central Weather Administration since September 15, 2023) revised its seismic intensity scale. National Taiwan University (NTU) has operated a low-cost earthquake early warning (EEW) system known as the P-Alert for a decade. In this study, we demonstrate the performance of the P-Alert network during the 2022 Chishang earthquake and the largest foreshock. The P-Alert network plotted shake maps during these earthquakes that displayed various values within 5 min. The high shaking areas on these maps were in good agreement with observed damages during this earthquake, providing valuable insights into rupture directivity, a crucial component of earthquake engineering. Individual P-Alert stations acted as on-site EEW systems and provided a lead time of 3–10 s within the blind zone of CWB. For the ML 6.8 mainshock, there was a lead time of at least 5 s, even up to 10 s, demonstrating their effectiveness in the blind zone. The P-Alert regional EEW system provided the first report about 9 s and 7 s after the mainshock and the largest foreshock occurrence, respectively, with estimated magnitudes of 5.74 and 5.67. The CWB system estimated magnitudes of 6.72 and 6.16 in the first report, respectively, about 7 s and 9 s after the earthquake occurrence. The timeliness of the two systems were not significantly different. Despite the effectiveness of the P-Alert network, data loss due to connection interruptions prompted us to develop a new compact data logger for improved data availability. [ABSTRACT FROM AUTHOR]

Introduction: Masonry minarets in Old Cairo are highly susceptible to earthquake damage, particularly those not designed or updated to withstand seismic loads. Therefore, regular monitoring is necessary to ensure their safety and detect any deterioration or reduction in seismic performance. The direct loss of a minaret can lead to the collapse or severe damage to the structure itself. The cascading impacts of partial or complete minaret failure can have significant consequences for the immediate vicinity and the broader community. By studying the effects of earthquakes on minarets and developing mitigation strategies, countries can take proactive measures to protect these structures and ensure the safety of people. Objective: This study focuses on a specific type of Islamic architecture: the historic minarets in Cairo. The research aims to evaluate the seismic vulnerability of eight cultural heritage minarets in Cairo, identifying the parameters influencing their seismic behaviour and susceptibility to earthquake damage. Methods: The research utilizes empirical seismic vulnerability methods and ambient vibration measurements on eight minarets. An empirical approach compatible with the nature and style of the minarets is employed to evaluate their vulnerability using index values and curves. The method's validity is assessed, and areas of conformity and limitations are identified. Ambient vibration tests (AVTs) are also conducted using a temporary seismic network installed at various heights inside each minaret to determine their dynamic characteristics. Results: The seismic vulnerability Index (I_V) is calculated for the selected minarets based on the state of each vulnerability parameter. The contribution of each parameter to the final I_V values of the minarets are presented. Vulnerability curves are developed for each minaret, interpreting the conventional vulnerability indexes in terms of mean damage grades for seismic events with varying intensity on the EMS-98 scale. These mean damage grades can also indicate the expected damage levels of structural and non-structural minaret elements for events with different seismic intensity levels. AVTs are conducted at various heights on the selected minarets, and the dynamic characteristics are extracted from the recorded data. Variations in these characteristics are considered significant for structural health monitoring analysis. The peak-picking method is employed to directly extract each minaret's natural frequencies and mode shapes, as changes in dynamic characteristics are relevant to health monitoring analyses. Conclusions: The recent study examined the seismic vulnerability assessment of eight masonry minarets in the historic Old Cairo district. The assessment revealed vulnerability index values ranging from 10.3 to 26.1, indicating a concerning susceptibility to seismic events among these structures. Vulnerability curves were constructed for each minaret, visually representing potential damage scenarios across different levels of the EMS-98 intensity scale. These outcomes are significant as they facilitate prioritizing interventions to safeguard the most vulnerable minarets. Additionally, a novel empirical period equation was introduced to estimate the fundamental period of minarets in Old Cairo based on their heights. The equation was validated against field measurements and data from the literature. The study is limited by its focus on a specific category of minarets, specifically the historical masonry minarets in Old Cairo. Furthermore, limitations arise from the need for detailed finite element models to capture these minarets' dynamic responses accurately. Therefore, ongoing research involves the development of detailed finite element models and calibrating fundamental periods for the selected minarets. The anticipated results hold the potential to enhance our understanding of the structural dynamics of historical minarets, ultimately guiding the formulation of tailored seismic retrofitting and preservation strategies. These strategies, aimed at preserving these cherished cultural heritage assets, represent our collective commitment to ensure the endurance of these timeless landmarks for future generations. [ABSTRACT FROM AUTHOR]

At 12:52 (UTC + 8) on September 5, 2022, an Ms 6.8 earthquake struck Luding County in Garzê Tibetan Autonomous Prefecture, Sichuan Province. This earthquake was characterized as a strike-slip event, with a focal depth of 16 km at 102.08°E and 29.59°N. As one of the pioneering emergent teams, the scientific personnel from the Institute of Geology, China Earthquake Administration immediately arrived at the site and conducted an extensive field investigation on earthquake-triggered landslides for half a month. The investigation results show that coseismic landslides are mainly distributed on both sides of the seismogenic fault and the Dadu River. Most landslides are concentrated within the regions with a seismic intensity of IX, such as the Moxi, Detuo, and Wanggangping towns. In particular, the Wandong and Xingfu villages have the highest abundance of landslides in the quake-affected area. These types of landslides are small- to medium-sized shallow landslides, collapses, and rolling stones with few larger-scale debris flows and slides. The loose deposits suspended at high position of a slope or in the valley of the quake-affected area are likely to slide again and generate new landslides or debris flows under the conditions of strong aftershock or heavy rainfall. Therefore, more attention should be paid to the long-term evolution of landslide activity and post-quake debris flows in the Luding area. [ABSTRACT FROM AUTHOR]

Based on the loess landslides induced by the 1654 Tianshui Ms 8.0 earthquake, the relationships among the landslide distribution and seismic intensity, epicentral distance, fault distance, original slope angle, and the strike of loess ridges were analyzed to better understand the geometric, directional, and kinematic characteristics of loess seismic landslides. The results show the following: (1) The seismic intensity and fault distance are remarkably correlated with landslide area, landslide number density, and landslide areal density, which are essential factors controlling earthquake-induced landslide development in the Tianshui area. (2) The landslides triggered by the Tianshui earthquake predominantly developed on gentle slopes, and the dominant original slope angles of the landslides range from 10 to 20°. The Tianshui earthquake-induced landslides are mainly large scale, accounting for 62.01%. (3) The main sliding directions of the landslides are concentrated at 220°–230° and 260°–270°, which are relatively the same as the aspect of the original slope. The correlation between the main sliding direction of landslides, strike of the loess ridges, and relative epicenter azimuth shows that the sliding direction of the Tianshui earthquake-induced landslides is not only affected by the propagation direction of seismic waves and strike of loess ridges, the loess thickness and stratum structure may also serve as the main factors controlling the development of the landslides. (4) The equivalent friction coefficient (μ) of the landslides induced by the 1654 Tianshui Ms 8.0 earthquake is between 0.1 and 0.6, with an average value of 0.27. The empirical relationships between the landslide volume (V) and equivalent friction coefficient, maximum horizontal distance of the landslide (Lmax), and maximum vertical distance of the landslide (Hmax) show that the Tianshui earthquake-induced loess landslides have a significant scaling effect and are characterized by low-angle and long-distance slip. The findings of our study constitute a solid base for further research on the mechanism and risk assessment of seismic-induced loess landslides and provide engineering application value. [ABSTRACT FROM AUTHOR]

Early disaster responses in damaged areas after a large earthquake are indispensable for stakeholders to assess and grasp the impacts such as building and infrastructure damage and disrupted community functionality as soon as possible. This study introduces a quick estimation model for mapping seismic intensities and building losses in Bogotá, the capital city of Colombia. The model uses ground motion records in the seismic network, soil maps of average shear-wave velocity in the upper 30 m (Vs30) with site amplifications, building inventory, and vulnerability functions for all building types. The spatial distribution of ground motion intensities, including spectral accelerations, was estimated by interpolating the observed seismic intensities with the Vs30-based site amplifications. The losses (repair cost) for all the buildings were evaluated by integrating the estimated spectral accelerations, the building inventory, and the vulnerability functions. The spatial distributions of seismic intensities and building losses can be computed within a few minutes immediately after triggering earthquake motions in the seismic network. The proposed model demonstrates evaluations of the impacts for the Mw6.0 earthquake that occurred on December 2019 and an earthquake scenario with Mw7.0 from an active fault near the Bogotá region. [ABSTRACT FROM AUTHOR]

This study is devoted to application of some new statistical methods to analysis of the spatial structure of the seismic field in a seismically active region in the neighborhood of Japan bounded by the following coordinates: 28°–50° north latitude, 130°–150° east longitude. The estimates of the seismic flux were obtained by using the k-nearest neighbors method for the magnitude interval m ≥ 5.2. The highest values of seismic flux intensity of about 10–4 are located at depths of down to 100 km and manifest themselves in the neighborhood of the Tohoku megathrust earthquake. The spatial resolution of the intensity estimates is ranging from 33–50 km in the regions with a high intensity to 100 km and larger in the zones with a weak intensity. It has been shown that the seismic filed parameters—intensity λ, slope of the magnitude–frequency graph β, maximum possible magnitude m1—have different scales of their spatial variability and, thus, it is necessary to apply different scales of spatial averaging to them. Based on the Gutenberg—Richter truncated distribution model, the estimates are obtained for the slope of the magnitude–frequency graph (b‑value) and the upper boundary of the distribution m1. An original method is proposed for determining the optimal averaging radius for an arbitrary cell of the space grid. The method is based on the use of the statistical coefficient of variation of the corresponding parameter. For the considered region, the estimate of the maximum possible magnitude Мmax= 9.60 0.41 was obtained with consideration of the correction for bias. [ABSTRACT FROM AUTHOR]

In this article we describe and interpret disturbances in the sedimentary records of four lakes on the western flank of Lake Imandra (NE Fennoscandia, Kola Peninsula). The research framework comprises sedimentological and textural criteria for a visual description of sedimentary structures sediment core data, chronological (radiocarbon dating) data, and ground-penetrating radar (GPR) data. Disturbances preserved in lake sequences contain a mixture of chaotic fragments of sand, silt, polychromatic gyttja, peat, and wood fragments embedded in the organogenic matrix. The synchronicity of disturbances, fast sediment accumulation in lakes, relationship with Quaternary faults, the observed mass movements in lake sediments are interpreted as potential consequences of the earthquake shaking. A seismic event with a magnitude Mw no less than 4.5–5 and intensity of shaking I 0 = IV–VI took place in the Middle Holocene, 6400–6100 cal. yr BP. Our studies show that although this area is not seismically active today, some of the main fault zones experienced short periods of reactivation also in the postglacial time, when glacioisostatic rebound after the ice retreat was already very low. [ABSTRACT FROM AUTHOR]

Early warning systems can estimate the possible-shaking intensity of the earthquake based on the initial P-waves on-site. Researchers have used the following two indicators: the initial peak P-wave displacement ( P d ) and the ground motion characteristic period ( τ c ). In this study, we re-examine the performance of the two indicators by employing ground motion data from the P-Alert low-cost network in Taiwan. We have found that the signal-to-noise ratio of displacement ( S N R d ) is effective for data selection. In addition, we have observed the irregular behavior of τ c in the P-Alert dataset. [ABSTRACT FROM AUTHOR]

Emergency authorities are concerned with how to effectively deliver patients to different hospitals for treatment while not overwhelming any single hospital during emergencies. This study proposes an optimization model for the real-time dispatching and treating schedule to evaluate the seismic resilience of the interdependent transportation-healthcare system. The functionality of the road network, the service of hospitals, and emergency management are comprehensively considered in the model. A series of case studies were used to test the applicability of the method and quantify the resilience under three seismic intensities. [ABSTRACT FROM AUTHOR]

From November to December 2015, shaking table experiments were conducted on a ten-story reinforced-concrete building to acquire useful data for developing advanced technology for seismic structures and to investigate numerical analysis models. Two structural system types, which are a free-standing base-sliding and conventional seismic structure system, were used in this experiment; the second system was the same building as the first, but with a fixed base. The specimen building was subjected to Kobe earthquake motions with amplitudes of 10%, 25%, 50%, 100%, and 60%. The experimental results of the free-standing base-sliding and conventional seismic structures were compared, and regression analysis was conducted on the relationship between the seismic performance of each structure and seismic intensity. During the Kobe earthquake with 100% amplitude, the peak maximum inter-story drift ratio of the free-standing base-sliding was smaller than that of the conventional seismic structure. The acceleration response distributions for the free-standing base-sliding and conventional seismic structure system experiments with smaller amplitudes were similar to the distribution provided by the Architectural Institute of Japan. The shear force coefficient at the base-sliding surface did not fluctuate significantly, despite the increase in sliding velocity. According to the regression analysis results, the global rotation stiffness ratio and equivalent story stiffness ratio of each story may be related to the cumulative value of the peak velocity of the shaking table; further, the peak maximum inter-story drift ratio may be linearly related to the seismic intensity. [ABSTRACT FROM AUTHOR]

Two models of the 10-story reinforced concrete building tested at E-Defense laboratory in 2015 are built: the F model, in which nonlinear behavior is distributed over the element length, and the H model, in which nonlinear behavior is lumped in plastic hinges with a moment-chord rotation response assigned based on empirical formulations proposed in the literature. Nonlinear time–history analyses are performed to reproduce the experimental shaking-table tests performed at increasing seismic intensity level. The incremental experimental test has been performed twice: the first time (BS test), the structure base was free to slip on a concrete base fixed to the shaking table. After the BS test, a second test was performed on the same structure with the foundation fixed to the concrete base (BF test). Both tests are simulated for both models. When simulating both the BS and BF tests, the seismic input adopted for the numerical analyses is the displacement time-history registered at the base of the specimen's columns, in order to implicitly account for base slip through the input signal without explicitly modeling the slipping devices. It is observed that the significant damage experienced by the specimen during the runs of BF tests at medium–high seismic intensity is probably triggered by softening and damage of beam-column joints: this is reproduced also by H numerical model and highlights the influence of beam-column joints on the overall seismic response of the structure. In general, it is observed that both numerical models, which were constructed, based on experimental data, only by adopting available and well-established tools proposed in the literature, can reproduce the overall response of the case-study structure, especially in terms of maximum top displacement demand and maximum damage state for structural members, provided that beam-column joints' contribution is adequately considered. [ABSTRACT FROM AUTHOR]

We analyze seismicity catalogues and find the periodicity of earthquakes in some regions of the northwest Himalaya. In particular, we identify spatiotemporal patterns in the distributions of earthquake occurrence. Earthquake sequences from 1963 to 2017 and 1991–2017, complete for magnitudes M ≥ 4.3 and M ≥ 3.3, respectively, are used to inspect the spatial b-value variation and hidden periodicities for three different regions. The thrust-dominated tectonic block of the Garhwal–Kumaon Himalaya favours more frequent occurrence of strong (large) earthquakes than the Kangra–Kinnaur sector dominated by nappe tectonics. Accompanied by the well-defined pattern of seismic quiescence-enhancement, the time-evolution periodicities have different behaviour associated with strong earthquakes, namely, the Mw 6.6 Chamoli earthquake of 1999 and Mb = 6.6 Uttarkashi earthquake of 1991. An increase in the amplitude of the periodicity in the period range of ~500 days appears ~0.5 years before the mainshock. The pre- and co-seismic periods of the 2012 earthquake of M 5.1 in the Delhi–Haridwar region highlight a strong high-amplitude periodicity in the period range of ~500–1000 days. This indicates that monitoring time-frequency dynamical spectra in near real-time can serve as a helpful guide in identifying hidden periodicities in earthquake sequences. [ABSTRACT FROM AUTHOR]

The northern part of Pemalang City consists of Quaternary deposits, having the potential for earthquake amplification effect. This amplification effect amplifies the ground shaking because of an earthquake (the local site effect) that has the potential to cause damage. This study investigated the amplification factor from the HVSR curve of microtremor measurements due to soil response based on ground shear strain, the risk level of the earthquake based on peak ground acceleration (PGA), and earthquake intensity. The microtremor data from five locations in Pemalang were used to calculate the amplification factor and predominant frequency. The damaging earthquake parameters around Java during 2010-2020 were used to calculate the PGA. The microtremor data were processed using the HVSR method, and PGA was calculated using the Kanai equation. The HVSR result shows that Pemalang has an amplification factor ranging from 6.23 to 19.59 and ground shear strain varying between 0.86 x 10-4 and 6.67 x 10-4, which shows that Pemalang only experiences the vibration when an earthquake occurs. The PGA results using the Kanai equation (19.71-54.56 gal) were included in the low vulnerability category, and MMI earthquake intensity (3.08-4.70) was included in the felt earthquake category (II SIG BMKG scale). Therefore, the amplification factor from the HVSR curve of microtremor measurement, ranging from 6.23 to 19.59, showed low soil response and low-risk vulnerability based on the damaging earthquake parameter around Java during 2010-2020. [ABSTRACT FROM AUTHOR]

To investigate the isolation effect of the friction pendulum system (FPS) horizontal isolation bearing and the air spring‐FPS three‐dimensional (3D) isolation bearing in truss structure and the influences of long‐period ground motions on the isolated structure, the shaking table test of a truss structure is designed and conducted. The ordinary ground motions, near‐fault pulse‐like ground motions, and far‐field long‐period ground motions with different spectral characteristics are chosen to input into the structure, and the dynamic characteristics such as the acceleration, displacement, and stress of the truss are compared and analyzed. The horizontal frequency of the horizontal isolated structure is reduced after the horizontal isolation, while the vertical frequency is further reduced after 3D isolation. The isolation effect of nodal acceleration, nodal displacement, and member stress under 3D isolation is better than that of horizontal isolation, especially the vertical seismic response is significantly improved. When the ground motion intensity is small, the FPS horizontal isolation bearing slides little, and reducing the seismic response of the structure is limited. There is a better isolation effect of 3D isolated structure. The vertical frequency ratio Rf under ordinary ground motions is far away from 1 and close to 3, basically avoiding the main energy segment of the ground motions. The advantage of 3D isolated structure is relatively reduced under long‐period ground motions, which lies in the rich low‐frequency components of long‐period ground motions which are difficult to isolate effectively. [ABSTRACT FROM AUTHOR]

There has been no consensus on post‐earthquake operating plan for high‐speed railway trains. In this paper, two three‐dimensional coupling model of track‐bridge system without and with trains for high‐speed railways were developed, and their performance were verified based on shaking table tests. The equivalent method of design seismic track irregularity for random structures was discussed, and the amplitude response spectra of design seismic track irregularity for all levels of seismic intensity were proposed. In addition, the rationality of design seismic track irregularity was evaluated based on engineering case analysis, providing a theoretical foundation of formulating post‐earthquake contingency plans for high‐speed railways. The results show that when span number increases, the design seismic track irregularity amplitude increases and then tends to be stable; when the span number reaches 9, the train dynamic response gradually becomes stable; the random structures with arbitrary span numbers are equivalent to a specific 9‐span structure when constructing design seismic track irregularity. When the seismic intensity is low, there is no significant difference in shape and amplitude between the measured pre‐earthquake and post‐earthquake track alignment irregularities, and the train can normally run with no significant deceleration required. The train dynamic response under the design post‐earthquake track irregularity is greater than that under the measured post‐earthquake track irregularity, indicating that the design seismic track irregularity has a reasonable safety margin and a good feasibility in engineering practice. [ABSTRACT FROM AUTHOR]

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This manuscript investigates the bias introduced by scaling aftershock ground motions when evaluating the performance of structures subjected to earthquake sequences. The study focuses on different hysteretic behaviors exhibited by structures and selects eight intensity measures as scale indicators. A benchmark database comprising 274 recorded mainshock–aftershock ground motions is utilized for analysis. The findings reveal that scaling aftershock records using intensity measures such as SI (seismic intensity), PGV (peak ground velocity), IC (Arias intensity), and Sa (spectral acceleration) relative to mainshock records effectively controls the mean bias within 30% throughout the entire period range, given a maximum scale factor of 10.0. However, it is observed that the additional damage in systems exhibiting un-degrading hysteretic behavior is more significantly affected by aftershock ground motion scaling compared to systems with degrading hysteretic behavior. Furthermore, scaling aftershock ground motions upwards using relative Sa tends to overestimate the additional damage incurred by structures. These results emphasize the importance of considering the specific hysteretic behavior of structures when applying aftershock ground motion scaling, as well as selecting appropriate intensity measures for accurate evaluation of structural performance. [ABSTRACT FROM AUTHOR]

The Southern San Andreas Fault (SSAF) in California is one of the most thoroughly studied faults in the world, but its configuration at seismogenic depths remains enigmatic in the Coachella Valley. We use a combination of space geodetic and seismic observations to demonstrate that the relatively straight southernmost section of the SSAF, between Thousand Palms and Bombay Beach, is dipping to the northeast at 60–80° throughout the upper crust (<10 km), including the shallow aseismic layer. We constrain the fault attitude in the top 2–3 km using inversions of surface displacements associated with shallow creep, and seismic data from a dense nodal array crossing the fault trace near Thousand Palms. The data inversions show that the shallow dipping structure connects with clusters of seismicity at depth, indicating a continuous throughgoing fault surface. The dipping fault geometry has important implications for the long‐term fault slip rate, the intensity of ground shaking during future large earthquakes, and the effective strength of the southern SAF. Plain Language Summary: The San Andreas Fault (SAF) is capable of large, destructive earthquakes and poses significant seismic hazard in California. In the Coachella Valley, the geometry of the SAF beneath the Earth's surface has been the subject of much debate. Here, we present new constraints on the fault's structure in the uppermost 2–3 km of the crust from several new sets of observations. We measure slow movement of the fault at the surface using satellite‐based radar and perform simulations of what fault geometry is most likely to produce the observed motion. We also installed an array of sensors across the SAF to measure seismic waves that travel through or reflect off the fault. Analysis of both data sets indicates that the shallow portion of the SAF dips to the northeast in the Coachella Valley. Precise locations of small earthquakes at greater depths exhibit a similar trend—we thus suggest the fault dips throughout the Earth's crust. Better understanding the geometry of this section of the SAF has implications for earthquake hazards in Southern California, as well as the fault's geologic history. Key Points: InSAR measurements and models of shallow creep on the southernmost San Andreas Fault indicate a moderate‐to‐steep northeast fault dipSeismic imaging using data from a dense array deployed near Thousand Palms reveal northeast dipping fault damage zonesA joint interpretation of available data suggests that the northeast dip persists throughout the upper 10 km of the crust [ABSTRACT FROM AUTHOR]

Geological faults impair tunnel stability during earthquakes. This study establishes a tunnel dynamic stability evaluation index based on load/unload response ratio (LURR) theory. It considers a seismic wave as a load/unload parameter and tunnel structure strain response as a response parameter. The rationale behind this evaluation index and the factors affecting tunnel stability across fault zones under seismic conditions are investigated. Compared to the traditional dynamic instability criterion, the LURR accurately measures the degree of structural deviation from the steady state and better determines the potential destabilization region of the structure. As the peak value of the input seismic wave increases, the LURRs of the more unstable parts increase, while the LURRs of the stable parts remain unchanged. According to LURR theory, the size of the range affected by the fault on the tunnel during an earthquake depends mainly on inherent fault properties (i.e., the dip angle, strike, and thickness), independent of the earthquake intensity. Because the LURR can theoretically be infinite, its dynamic instability threshold cannot be determined accurately. [ABSTRACT FROM AUTHOR]

The façade system is one type of building envelope. It is both acceleration sensitive and displacement sensitive under dynamic loads. However, some novel complex façade systems lack comprehensive study, especially under earthquake excitations, and full-scale shaking table test for both façade system with the main structure is expensive. Thus, a test design procedure is proposed, which includes the input excitations into the façade by using the finite element method (FEM) model, and aims for achieving acceleration and drift demands for acceleration-and-displacement sensitive nonstructural components (NCs). According to this procedure, full-scale shaking table tests for the façade system only are designed and conducted under different earthquake intensity levels. The responses (such as acceleration and displacement) are recorded, and critical damages (such as the relative residual displacement between panels and bolt scratch) are observed. Several key factors that affect the seismic performance, such as the component acceleration amplification factor and the required distance to prevent collision between panels, are discussed. [ABSTRACT FROM AUTHOR]

The code-based response modification factors are mainly developed based on engineering judgments and experiences from past earthquakes, and hence, they may not lead to reliable solutions considering different performance targets and hazard levels. On the other hand, the uncertainties associated with these proposed values are more significant for new lateral load-carrying systems, such as tunnel-form buildings, due to insufficient information about their performance against seismic events. To address these challenges, this study aims to propose a multi-level approach for the estimation of response modification factors for tunnel-form building structures by taking into account the site seismicity and the damage level defined as the target performance. Using the proposed approach, the modification factors corresponding to different ranges of earthquake intensity and damage levels are obtained for 2-, 5-, 7-, and 10-storey tunnel-form buildings. The results are then used to verify the efficiency of the response modification factors proposed by design codes for the preliminary design (code-based factors) of such systems. It is shown that, in general, by adopting a response modification factor between 4 and 6, the tunnel-form structural systems exhibit excellent seismic performance and can satisfy the requirements of the Immediate Occupancy (IO) performance level even under the Maximum Considered Earthquake (MCE). The outcomes of this study could be useful for performance-based design of tunnel-form building structures aligned with the new generation of seismic design codes. [ABSTRACT FROM AUTHOR]

This study is aligned with United Nations, Sustainable Development Goal 11, concerned about making cities and human settlements inclusive, safe, resilient and sustainable, in particular, in line with resilience to disasters, and protecting the world's cultural heritage targets. Focused on a small sample of rammed earth residential dwellings in the city of Mula, one of the areas of highest seismic hazard in Spain, the seismic vulnerability has been assessed adapting the Vulnerability Index Method (Risk-UE) to tackle the specificities of earthen residential buildings. The majority of this humble earthen heritage, despite being an essential part of the Spanish Culture, suffers from the effects of abandonment and insufficient maintenance. As a consequence, these genuine buildings will be seriously damaged in the event of an earthquake of intensities from VII to VIII, with heritage losses representing 17% to 43% of the built area. These research outcomes can be used to define repair and strengthening priorities among the buildings in the sample when financial resources are limited. The proposed indices and coefficients can be applied to similar earthen structures, widely built in the Iberian Peninsula and the Mediterranean region. [ABSTRACT FROM AUTHOR]

The results of experiments on simultaneous recording of seismic signals from various sources on the Earth surface and at a depth of up to 250 m are stated. The peculiarities of change with depth of the spectral composition of teleseismic earthquake and microseismic oscillations have been studied, which testify in favour of a significant decrease in the level of seismic effects on underground structures in a wide range of frequencies in relation to buildings and structures on the daylight surface. [ABSTRACT FROM AUTHOR]

Peak ground acceleration (PGA) is one of the critical factors that affect the determination of earthquake intensity. PGA is generally utilized to describe ground motion in a particular zone and is able to efficiently predict the parameters of site ground motion for the design of engineering structures. Therefore, novel models are developed to forecast PGA in the case of the Iraqi database, which utilizes the particle swarm optimization (PSO) approach. A data set of 187 historical ground-motion recordings in Iraq's tectonic regions was used to build the explicit proposed models. The proposed PGA models relate to different seismic parameters, including the magnitude of the earthquake (M w), average shear-wave velocity (V S 30), focal depth (FD), and nearest epicenter distance (R EPi) to a seismic station. The derived PGA models are remarkably simple and straightforward and can be used reliably for pre-design purposes. The proposed PGA models (i.e., models I and II) obtained via the explicit formula produced using the PSO method are highly correlated to the actual PGA records owing to low coefficients of variation (CoV) of approximately 2.12% and 2.06%, and mean values (i.e., close to 1.0) of approximately 1.005 and 1.004. Lastly, high-frequency, low absolute relative error (ARE), which is below 5%, is recorded for the proposed models, thereby showing an acceptable error distribution. [ABSTRACT FROM AUTHOR]

Evaluation of the seismic performance of two historical stone arch bridges of the Iranian rail network is presented using a discrete element method. The total length of the bridges is 66.7 m and 106.1 m. The bridges consist of multi-span arches changing from 5 m to 48.6 m. The incremental dynamic analysis method is used to determine the damage, failure patterns, and acceleration of the collapse threshold. Using the discrete element method after static analysis under gravity load, dynamic analysis of bridges under both horizontal components of the earthquakes was performed simultaneously for different earthquake intensities until collapse. The results showed that the most extensive damage occurred in the smaller bridge with the onset of failures in the top spandrels of the arches and then the piers of the bridge, while in the larger bridge which had a large central arch span, damage and failure occurred more in the central arch and its spandrels. The collapse spectral acceleration of the larger bridge is considerably smaller than the smaller bridge such that the ratio of collapse spectral acceleration of the larger to smaller bridge varies only between 45% to 61%. The low spectral acceleration intensity of collapse indicates more seismic vulnerability of the larger bridge. [ABSTRACT FROM AUTHOR]

Precariously balanced rocks (PBRs) are a type of naturally occurring freestanding structure that provides valuable information to constrain seismic hazard at return periods which are important for critical facilities such as nuclear power plants and nuclear repositories. Exposure ages have been established to be in excess of 10,000–30,000 years, which is why precarious rocks are one of the only available means to validate seismic hazard associated with long return periods. One critical component for constraining seismic hazard in this way is the overturning estimate of a given precarious rock as a function of earthquake intensity. However, current state‐of‐the‐art methods for modeling the seismic response of precarious rocks involve significant sources of uncertainty. One of the main sources of uncertainty stems from the interface of the rock, which is usually occluded during surveying and assumed during modeling. Through extensive shake table testing, this study analyzes the uncertainty in the overturning response of a granite precarious rock specimen incorporating various degrees of interface contact. The results indicate that a small variation in the contact geometry could result in a substantial increase in the stability of the specimen, which is significant given the difficulty of surveying the interface of PBRs in the field. Repeatability tests indicate that the overturning demand can vary up to nearly ±50%. The probabilistic overturning responses are compared across the interface changes to bound uncertainty; and, the effect of modeling parameters, namely the contact normal stiffness, is evaluated through a parametric study and comparison with experimental results. [ABSTRACT FROM AUTHOR]

Fires and earthquakes can be present simultaneously. One primary scenario comes from strong earthquakes, followed by aftershocks, and sometimes causing post-earthquake fires. Another primary scenario starts with a fire, and followed by an earthquake. This study explored the effects of horizontal earthquakes on the structure and behaviors of free-burning fires. The horizontal seismic condition was simulated using a vibrator, with wood cribs as the fuel. Experimental results indicate that the heat release rate increased with the increased seismic intensity, given that the fires encountering horizontal earthquakes burned faster than the free-burning ones. The HRR rise was a result of the earthquake enhancing the combustion efficiency and the surrounding air entrainment. Additionally, the induced vibration changed the structure of the fire, reduced the flame height and increased the fire-base diameter. Furthermore, this study proposed a HRR and a flame height correlations under horizontal seismic conditions. [ABSTRACT FROM AUTHOR]

The earthquake in Kahramanmaraş, Turkey, on February 6, 2023, was recorded as one of the most severe earthquakes recently. Because of the magnitude of the intensity of the earthquake and its coverage of many provinces, it had devastating effects. In addition to the impact of the disaster after the quake, the emergence and spread of infectious diseases were facilitated by insufficient safe water, housing problems, inadequate nutrition, inadequate hygiene conditions, and many individuals living in public areas. In this context, respiratory tract infections, gastrointestinal infections, skin infections, and vectorborne infections are more common after disasters. Necessary measures should be taken to establish an effective surveillance system for preventing and protecting infectious diseases after the earthquake, plan new settlements, continue immunization services, access safe water, and provide adequate and balanced nutrition, sanitation, vector control, and health education. [ABSTRACT FROM AUTHOR]

Recent studies showed that while code-compliant structures can generally protect the safety of the occupants, they may exhibit extensive damages during strong earthquake events. On the other hand, structures are generally designed to satisfy the seismic code requirements with the least initial cost regardless of their life cycle cost. In recent years, value-based design has been considered as an effective alternative for code-based design procedures. In this method, as well as the initial cost of the structure, a comprehensive consequence modeling is performed in the design process. In this paper, for the first time, a value-based design optimization method is developed for seismic enhancement of existing RBS steel frames using nonlinear viscous dampers. The efficiency of the method is demonstrated through 4-, 8-, and 12-story frames designed for low, medium, and high earthquake intensity levels, while the life cycle costs are evaluated using FEMA P-58. A time-based approach is carried out to consider different earthquake events and their corresponding probability of occurrence in a specific range of intensities. For dynamic analysis of the structures, the Endurance Time (ET) method is adopted to significantly reduce the computational costs while providing accurate results. The Genetic Algorithm (GA) is then used to optimize the damping coefficient of the viscous dampers for minimum life cycle cost. The results, in general, indicate the efficiency of the proposed method in increasing the total economic value of the studied structures with the least additional cost. It is shown that shorter structures and those designed in high-seismic risk regions benefit more from using optimized viscous dampers, leading to up to 42% lower life cycle costs. The results of this study should prove useful in more efficient strengthening design of existing steel frames. [ABSTRACT FROM AUTHOR]

Past earthquakes have highlighted the impact of prolonged downtime on community recovery. The introduction of performance objectives expressed in terms of recovery time has been identified as a key goal for the next generation of building codes. Recent development of downtime estimation frameworks now allows for the discussion of how to use recovery time estimates to (1) establish recovery‐targeted performance and (2) assess the functional recovery performance of buildings designed with modern code provisions. In this paper, we employ methods adapted from life‐safety provisions to evaluate building functional recovery performance using downtime simulation outputs. A scenario‐based, an intensity‐based and a risk‐targeted analysis of functional recovery performance objectives are presented. The functional recovery performance of a series of modern residential reinforced concrete shear wall archetype buildings, ranging from eight to 24 stories in height, at a site in downtown Seattle, Washington, are then assessed. Results of the scenario‐based assessment of an M9 Cascadia Subduction zone earthquake, comparable to an intensity‐based assessment at the 975‐year intensity level, show that the probability of achieving functional recovery within four months is close to zero, while the likelihood of achieving functional recovery by one year is approximately 60%. The results of the risk‐targeted assessment of the archetype buildings show a 50% probability in 50 years of the building downtime to functional recovery exceeding one month, a 43% in 50‐year probability of the downtime exceeding four months and an 8% in 50‐year probability of downtime exceeding one year. Finally, the expected annual downtime is approximately three days for all building heights considered. Disaggregation was used to identify intensity levels that contribute most of the downtime risk. The risk of downtime exceeding one month to one year is dominated by frequent, low‐intensity earthquakes (e.g., 100‐year return period). The risk of exceeding longer recovery times is dominated by less frequent, higher intensity earthquakes (i.e., return periods greater than 975 years). While the results of the analysis are sensitive to assumed damage thresholds and impeding factor delays triggered at low intensity levels, the findings suggest that reinforced concrete shear wall buildings designed following current building codes have a high risk of lengthy downtimes. Ultimately, the proposed methods and results illustrate the importance of introducing recovery‐based provisions into the next generation of building codes. [ABSTRACT FROM AUTHOR]

Although Myanmar is an earthquake-prone country, there has not been proposed an official national seismic hazard map. Thus, this study conducted a probabilistic seismic hazard assessment for Myanmar and some of its metropolitan areas. Performing this assessment required a set of databases that incorporates both earthquake catalogs and fault parameters. We obtained seismic parameters from the International Seismological Centre, and the fault database includes fault parameters from paper reviews and the database. Based on seismic activities, we considered three categories of seismogenic sources—active fault source, shallow area source, and subduction zone source. We evaluated seismic activity of each source based on the earthquake catalogs and fault parameters. Evaluating the ground-shaking behaviors for Myanmar requires evaluation of ground-shaking attenuation; therefore, we validated existing ground motion prediction equations (GMPEs) by comparing instrumental observations and felt intensities for recent earthquakes. We then incorporated the best fitting GMPEs into our seismic hazard assessments. By incorporating the Vs30 (the average shear velocity down to 30 m depth) map from an analysis of topographic slope, we utilized site effect and assessed national probabilistic seismic hazards for Myanmar. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault and along the Western Coast of Myanmar. We also assessed seismic hazard for some metropolitan cities, including Bagan, Bago, Mandalay, Sagaing, Taungoo and Yangon, in the forms of hazard curves and disaggregation by implementing detailed Vs30 maps from micro-tremor surveys. The city-scale assessments show higher hazards for sites close to an active fault or/and with a low Vs30, demonstrating the importance of investigating site conditions. The outcomes of this study will be beneficial to urban planning on a city scale and building code legislation on a national scale. [ABSTRACT FROM AUTHOR]

The performance of clay-pile-pier system under earthquake shaking was comprehensively examined via three-dimensional finite element analyses, in which the complex stress-strain relationships of a clay and piled pier system were depicted by a hyperbolic-hysteretic and an equivalent elastoplastic model, respectively. One hundred twenty ground motions with varying peak accelerations were considered, along with the variations in bridge superstructure mass and pile flexural rigidity. Comprehensive comparison studies suggested that peak pile-cap acceleration and peak pile-cap velocity are the optimal ground motion intensity measures for seismic responses of the pier and the pile, respectively. Furthermore, based on two optimal ground motion intensity measures and using curvature ductility to quantify different damage states, seismic fragility analyses were performed. The pier generally had no evident damage except when the bridge girder mass was equal to 960 t, which seemed to be comparatively insensitive to the varying pile flexural rigidity. In comparison, the pile was found to be more vulnerable to seismic damage and its failure probabilities tended to clearly reduce with the increment of pile flexural rigidity, while the influence of the bridge girder mass was relatively minor. [ABSTRACT FROM AUTHOR]

Based on the deflection behavior of structural components occurring at the lateral deformation of moment frames, a new lateral force-resisting system, the R-BRACE Frame (RBF) system, was proposed. This system is capable of effectively limiting the inter-story drift response of tall buildings. An evaluation was conducted using the finite element method program SAP2000 to simulate the internal force distribution and deformation of the system. The equivalent lateral force procedure (ELFP), the capacity spectrum method (CSM), a linear time-history analysis and the pushover method were applied to assess the yielding mechanism of the structure under different earthquake intensity levels. The findings revealed that the sub-unit, referred to as an R-BRACE, had a major impact on improving a structure's lateral stiffness. The placement of R-BRACE units could guarantee controllable stiffness degradation and enhanced seismic ductility, but would not alter the vertical load transfer path of the initial structure, which makes the RBF system an ideal option for seismic retrofitting. [ABSTRACT FROM AUTHOR]

Landscapes disturbed by shallow landslides present several residual risks. For example, residual soils on sliding surfaces may lead to the re-occurrence of shallow landslides, and landslide deposits on valley floors may introduce multiple hazards associated with river blocking or landslide damming. Despite such risks, few studies have investigated the residual risks following shallow landslides, and thus, no methodology has been established for assessing such risks. In this study, we combined portable cone penetration test (PCPT) and electrical resistivity tomography (ERT) to investigate the post-event risks associated with a landslide scar resulting from the 2018 Hokkaido Eastern Iburi earthquake (HEIE) in Japan. The multi-point PCPT identified the interface between a weak volcanic soil layer and underlying weathered sedimentary rocks. This interface exhibited an abrupt spatial change in resistivity, ranging from 20 to 100 Ωm. The thickness of the residual soil layer was 0.3–3.2 m and that of the landslide deposit exceeded 2.0 m. An infinite-slope stability analysis was performed to predict the re-occurrence of shallow landslides due to a lower intensity earthquake than that of HEIE in this region. Considering the area affected by the HEIE and the physical properties of soil layers, our findings imply a widespread risk of re-occurrence of shallow landslides over an area of 20 km × 20 km. Although the areal coverage of the combined ERT/PCPT method needs to be extended, it is effective for assessing the residual risks associated with shallow landslides. [ABSTRACT FROM AUTHOR]

The spatial estimation of the soil response is one of the key ingredients for the modelling of earthquake risk. We present a ground motion amplification model for Switzerland, developed as part of a national-scale earthquake risk model. The amplification model is based on local estimates of soil response derived for about 240 instrumented sites in Switzerland using regional seismicity data by means of empirical spectral modelling techniques. These local measures are then correlated to continuous layers of topographic and geological soil condition indicators (multi-scale topographic slopes, a lithological classification of the soil, a national geological model of bedrock depth) and finally mapped at the national scale resorting to regression kriging as geostatistical interpolation technique. The obtained model includes amplification maps for PGV (peak ground velocity), PSA (pseudo-spectral acceleration) at periods of 1.0, 0.6 and 0.3 s; the modelled amplification represents the linear soil response, relative to a reference rock profile with VS30 (time-averaged shear-wave velocity in the uppermost 30 m of soil column) = 1105 m/s. Each of these amplification maps is accompanied by two layers quantifying its site-to-site and single-site, within event variabilities, respectively (epistemic and aleatory uncertainties). The PGV, PSA(1.0 s) and PSA(0.3 s) maps are additionally translated to macroseismic intensity aggravation layers. The national-scale amplification model is validated by comparing it with empirical measurements of soil response at stations not included in the calibration dataset, with existing city-scale amplification models and with macroseismic intensity observations from historical earthquakes. The model is also included in the Swiss ShakeMap workflow. [ABSTRACT FROM AUTHOR]

Near-fault earthquakes can cause more intricate dynamic responses and potentially lead to severe damage to bridge structures compared to far-field earthquakes. In January 8, 2022, a 6.9-magnitude earthquake struck Menyuan, Qinghai Province, resulting in the disruption of the Lanzhou-Urumqi high-speed railway. The Liuhuanggou Bridge is the first high-speed railway bridge in the world to have undergone severe earthquake damage. In order to investigate the reasons for the seismic damage and girder falling mechanism, this study established a comprehensive nonlinear analysis model that considers the entire process from mild damage to complete failure of bridge components. Based on the LS-DYNA explicit dynamic analysis software, the model accurately simulates the collision, girder falling, and bearing damage. Based on limited field investigation data and combined with theoretical methods, reasonable seismic inputs are constructed, which accurately reproduce the bridge damage. The analysis results indicate that the girders and piers of high-speed railway simply supported bridges exhibit good seismic performance under seismic, while the bearings and shear keys are damaged. The seismic intensity (IX degree) significantly exceeded the fortification intensity (VII degree) of the bridge. The near-fault earthquake velocity pulse, inappropriate seismic measures, and nonuniform excitation of cross-fault earthquake are significant factors leading to the collapse of the Liuhuanggou Bridge. Further research is needed for the rational selection of bridge types in fault zones. The numerical results and conclusions of this study can provide a reference for the seismic design of high-speed railway simply supported bridges built near faults. [ABSTRACT FROM AUTHOR]

The determination of ground motion is crucial to plan the appropriate emergency activities, especially in areas characterised by an intense seismic history like the Italian peninsula. Ground motion assessment is generally based on the seismological parameters reported in the instrumental and parametric seismic catalogues. Therefore, the computation of shaking scenarios of historical earthquakes is very challenging, due to the poorly constrained variables (i.e., magnitudes, epicentral location, seismogenic sources), derived from the macroseismic intensity. In this study, we propose a novel approach to investigate the location and parametrization of the seismogenic sources of historical earthquakes and derive shaking scenarios. To this aim, the ground motion of two historical events, the Fabriano (1741, Mw = 6.1, Imax IX MCS) and Camerino (1799, Mw = 6.1, Imax IX–X MCS) earthquakes is simulated. In order to include the site response, a Vs,30 map of the Umbria and Marche regions is created from near-surface data. Different causative faults solutions are tested, finally discussing the ideal seismogenic source based on the residual analysis between observed and simulated macroseismic intensities. The resultant shaking scenarios of the two events are obtained by integrating observed intensities and simulations. [ABSTRACT FROM AUTHOR]

In this study, a pipe-soil finite element analysis model was built using the shaking table test results of buried pipelines that were achieved through longitudinal multipoint excitation and multipoint excitation under different seismic intensities, so as to numerically simulate the seismic response of buried pipelines under longitudinal multipoint excitation and multipoint excitation under different seismic intensities. As indicated by the result of this study, the numerical calculations and the shaking table test findings in terms of long-distance oil and gas pipelines under longitudinal multipoint stimulation were well consistent, such that the validity of both sets of results was verified. The peak pipe stresses during the multipoint excitation under different seismic intensities declined by 13.8% to 30.9% compared with case 2 longitudinal multipoint stimulation. The acceleration of the pipe and the soil was reduced rapidly as the measuring point moved farther away from the pipe's leftmost distance. The displacement variation of the oil and gas pipelines under longitudinal multipoint excitation suggested that the soil displacement was increased with the length of the monitoring point from the bottom of the soil box for different elevations of the same section. The soil displacement declined notably for the same stretch at the identical elevation with the reduction of seismic intensity. The findings of this study can lay a basis for in-depth research on the effect of multipoint stimulation with different seismic powers on the seismic response of underground pipes. [ABSTRACT FROM AUTHOR]

Studies on earthquake-related damage underscore that buildings are vulnerable to significant harm or even collapse during moderate to strong ground motions. Of particular concern is seismic-induced pounding, observed in numerous past and recent earthquakes, often resulting from inadequate separation gaps between neighboring structures. This study conducted an experimental and numerical investigation to develop a mathematical equation to calculate a sufficient separation gap in order to avoid the collision between adjacent mid-rise steel-frame buildings during seismic excitation. In this study, the coupled configuration of 15-storey & 10-storey, 15-storey & 5-storey, and 10-storey & 5-storey steel frame structures was considered in the investigation. The investigation concluded with a large number of data outputs. The outputs were used to predict structural behavior during earthquakes. The obtained data were categorized into three main categories according to the earthquake's Peak Ground Acceleration (PGA) levels. Also, the derived equations were divided into three different equations to estimate the required seismic gap between neighboring buildings accordingly. The derived equations are distilled to empower engineers to rigorously evaluate non-irregular mid-rise steel frame buildings. [ABSTRACT FROM AUTHOR]

The deformation of the track on bridge after the earthquake mainly includes bridge creep and seismic-induced deformation, which poses a serious threat to the running safety of trains. In order to study the influence of the comprehensive deformation on the train-bridge system, a three-dimensional model of train-bridge coupling analysis was established. New point estimation method was used to solve the stochastic problem of initial track irregularity, aiming to study the changes of system motion under different parameters including deformation degrees and train speed. Results show that system motion increases with the increase of track parameters, and the earthquake intensity has the greatest influence on the train the motion, which reaches the peak in 0.4 g. The train speed has the greatest influences on the bridge when the train speed reaches the peak value of 400 km/h, while the impact of bridge creep is the smallest. Conclusion was obtained that the results of random analysis are of more general significance, and that in the vehicle-bridge system considering comprehensive track deformation after earthquake, the damage effect of track deformation induced by earthquake intensity is mainly considered for train, and the impact of train speed shall be mainly considered in bridge design. [ABSTRACT FROM AUTHOR]

The China seismic instrumental intensity can be used to measure the level of destruction and serve as the foundation of earthquake early warning (EEW) systems. To indirectly develop the instrumental intensity estimation and its application to EEW, we estimated the on-site filtered peak ground motion velocity (PGV) of the intensity using a support vector machine (SVM)-based model with eight P-wave features at a 3-s time window. Alert thresholds were set when the PGV was ≥ 8.18 cm/s (VII on the instrumental intensity scale). Compared with two linear estimation models (IV2 and Pd), the mean absolute error (MAE) and standard deviation of the error of the SVM estimation model were less, 0.241 and 0.298, respectively, with better performance on the PGV estimation. To evaluate the feasibility of transforming the SVM estimation for EEW by issuing alerts based on the intensity scale, we used the accuracy, precision, recall, F1 score, and false-negative rate (FNR) as evaluation metrics, achieving values of 99.62%, 95.68%, 79.90%, 87.08%, and 20.10%, respectively, using 11,970 records. We also provided the ratio, maximum, and average of the true positives to evaluate the lead time performance. Meanwhile, we used six earthquakes to evaluate the performance of our approach in detail. The approach performed well on EEW applications by issuing alerts based on the China seismic instrumental intensity. The analysis of the feature importance and data balance strategy can provide the basis for improving the performance of the SVM-based PGV estimation model. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic damage behavior of steel pipe pile wharves after pitting corrosion. The seismic intensity is treated as random, and a probabilistic strength model for randomly pitting corroded steel is utilized to assess the seismic response of a typical steel pipe pile wharf. By analyzing the internal force response of each pile and the deformation response of the deck and soil slope, the process of seismic failure in steel pipe pile wharves with different pitting corrosion ratios is investigated. The results demonstrate that pitting corrosion amplifies the internal force within the steel pipe piles, leading to more severe seismic damage. Additionally, probabilistic seismic demand functions are established for the most vulnerable row of piles affected by random pitting corrosion, and the seismic fragility of the pipe pile wharves considering different pitting corrosion ratios is evaluated. These findings provide valuable insights for the design and strengthening of steel pipe pile wharves. [ABSTRACT FROM AUTHOR]

Damage identification plays an important role in enhancing resilience by facilitating precise detection and assessment of structural impairments, thereby strengthening the resilience of critical infrastructure. A current challenge of vibration-based damage detection methods is the difficulty of enhancing the precision of the detection results. This problem can be approached through improving the noise reduction performance of algorithms. A novel method based partially on the errors-in-variables (EIV) model and its total least-squares (LS) algorithm is proposed in this study. Compared with a classical damage detection approach involving adoption of auto-regressive (AR) models and the least-squares (LS) method, the proposed method accounts for all the observation errors as well as the relationships between them, especially in an elevated level of noise, which leads to a better accuracy. Accordingly, a shaking table test and its corresponding finite element simulation of a full-scale web steel structure were conducted. The acceleration time-series output data of the model after suffering from different seismic intensities were used to identify damage using the presented detection method. The response and identification results of the experiment and the finite element analysis are consistent. The finding of this paper indicated that the presented approach is capable of detecting damage with a higher accuracy, especially when the signal noise is high. [ABSTRACT FROM AUTHOR]

The western region of China is rich in hydropower resources and characterized by unique geological conditions. For the construction or planned construction of high dams in this region, different types of cover layers are formed due to special geological structures, most of which are located in high seismic intensity zones. This study focuses on four different site conditions: hard ground, medium–hard ground, medium–soft ground, and weak ground. By simulating the dynamic response of concrete-face rockfill dams under near-fault earthquake excitation, the vertical settlement of the dam and the attenuation of seismic motion under different site conditions are analyzed. The research findings reveal a consistent trend where the vertical settlement of the dams progressively escalates with increasing dam height across all four site conditions. This settlement phenomenon is especially pronounced in weak ground conditions, posing a potential risk of failure. Furthermore, when subjected to near-fault pulse-type earthquake motions, the existence of weak soil layers significantly dampens the seismic forces experienced by the dam. This finding suggests that the weaker the geological conditions of the site, the more pronounced the attenuation effect of the seismic motion. Additionally, the overburden layers have a noticeable amplification effect on near-fault pulse-type earthquake motion. However, this amplification effect is not significant in weak ground, possibly due to the presence of weak soil layers restricting the propagation and amplification of seismic motion. In conclusion, these research findings have practical significance for the dynamic response of high dam construction in different site conditions in the western region of China. They provide a scientific basis for the design and construction of high dams and serve as a reference for the implementation of seismic mitigation measures and earthquake disaster prevention in engineering projects. [ABSTRACT FROM AUTHOR]