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Conditional Spectrum (CS), characterized by a conditional mean and conditional standard deviation, serves as a target spectrum linking seismic hazard information to ground motion selection for seismic demand analysis. Current Ground Motion Selection and Modification (GMSM) methods aim to align with this target spectrum but face challenges due to the limited availability of recorded ground motions and potential modifications, leading to difficulties in ensuring selected ground motions accurately reflect site characteristics. Addressing this issue, the study presents an algorithm to select hazard-consistent CS-based records utilizing a stochastic ground motion model with a dual objective: (1) alleviate the need for scaling during the selection process, and (2) select records consistent with the target hazard and the contributing causal scenarios. To achieve both objectives, the study generates a database of hazard-targeted ground motions utilizing the kriging surrogate with scenarios sampled from the disaggregation matrix. Then, a postprocessing step explicitly considers causative parameters in the selection process. The algorithm's potential to select site-specific ground motions is demonstrated using sites in the Western United States, providing insights into the computational cost and accuracy. Additionally, statistical comparisons are conducted to explore circumstances where similar hazard consistency can be achieved without the postprocessing step, reducing the overall computational cost. Finally, the selected ground motions are favorably compared to those selected through traditional conditional spectrum-based approaches based on their spectral shape and ground motion intensity measures. [ABSTRACT FROM AUTHOR]

The diagrid structural system has become popular in the construction of high-rise buildings in light of significant advantages over other structural systems. The present study explores the effects of the vertical near-fault earthquake component on the axial forces of diagonal elements in steel diagrid structures. Nonlinear time-history analysis was carried out using 11 near-fault earthquake records. A total of nine three-dimensional models of 12, 18, and 24 stories, each with diagonal angles of 45, 63.4, and 71.5 degrees, were designed and analyzed. Due to the three-dimensional modeling complexities of diagrid structures, a method was developed to transform three-dimensional models into two-dimensional ones. Finally, the scenarios with and without the vertical earthquake component were compared. It was found that the incorporation of the vertical earthquake component into the analysis of diagrid structures substantially influenced the axial forces of diagonal elements. This can affect the design load estimation of diagonal elements as the main components of a diagrid structure. [ABSTRACT FROM AUTHOR]

Estimating an earthquake's magnitude and location may not be necessary to predict shaking in real time; instead, wavefield‐based approaches predict shaking with few assumptions about the seismic source. Here, we introduce GRAph Prediction of Earthquake Shaking (GRAPES), a deep learning model trained to characterize and propagate earthquake shaking across a seismic network. We show that GRAPES' internal activations, which we call "seismic vectors", correspond to the arrival of distinct seismic phases. GRAPES builds upon recent deep learning models applied to earthquake early warning by allowing for continuous ground motion prediction with seismic networks of all sizes. While trained on earthquakes recorded in Japan, we show that GRAPES, without modification, outperforms the ShakeAlert earthquake early warning system on the 2019 M7.1 Ridgecrest, CA earthquake. Plain Language Summary: Have you ever heard something through the grapevine? It often takes you by surprise to hear a message from someone other than the original source. You might have felt an earthquake in a similar way: experiencing shaking (the message) at your location rather than movement along a fault (the source). We apply grapevine‐style communication to earthquake early warning (EEW). The goal of EEW is to warn people to prepare for earthquake shaking before damaging seismic waves arrive at their location. We build on recent work that used deep learning and large earthquake data sets to predict earthquake shaking. We developed a deep learning algorithm called GRAPES which predicts shaking in a manner similar to a game of seismic telephone: when a seismic sensor detects shaking, it sends a message to its neighboring sensors, warning them to expect shaking soon. These sensors then pass on the message to their more distant neighbors along the grapevine. We show that the messages GRAPES learned to send between sensors are like seismic status updates: "I'm seeing this type of seismic wave right now". We applied GRAPES to the 2019 M7.1 Ridgecrest, CA earthquake and it predicted shaking accurately and quickly. Key Points: A deep learning network trained to predict ground motion learned an internal representation of the seismic wavefieldIndividual neurons within the network activate with the arrival of P waves, S waves, surface waves, coda waves, and ambient noiseWhile trained on earthquakes in Japan, the model generalizes well to predicting ground motions for the 2019 Ridgecrest, CA earthquake [ABSTRACT FROM AUTHOR]

A five story (G + 4) residential structure is positioned on 15°, 30°, and 45° slopes to be explored in this study in terms of vulnegrability and compared to the same structure resting on flat ground 0°. The RC frame models were constructed in accordance with Eurocode 8 and then subjected through a series of 10 ground motion records. In accordance with Vision 2000 performance limit states (PLS), this research provided the use of nonlinear static analysis (NL-SA) and nonlinear dynamic analysis (NL-DA) methodologies to assess seismic risk performance and vulnerability of structures resting on various slope angles. Incremental Dynamic Analysis (IDA) and Pushover Analysis (POA) capacity curves, as well as the fragility curve and the collapse margin ratio, are generated for the four selected models (M0, M15, M30, M45). The results show that the RC frame model M45, located on a 45°-degree incline, is the most vulnerable to damage. The risk of damage to the RC frame M0 is minimal because it is not elevated off the ground. To this end, the relative degrees of vulnerability among the frames were determined to be as follows: M45 > M30 > M15 > M0. [ABSTRACT FROM AUTHOR]

The damage assessment of numerous buildings after the earthquake is still a challenge by traditional methods as it requires a significant amount of time and resources for carrying out building-by-building seismic damage assessment. This study presents the machine learning (ML)-based damage assessment of buildings after an earthquake. The applicability of the machine learning model will be limited considering only structural properties or ground motion characteristics. Thus, in this study, the applicability of different machine learning techniques is explored using real-world earthquake damage datasets considering both the structural properties and ground motion characteristics. Initially, the entire dataset is used to train the ML models to classify the building's damage into five categories ranging from null to slight damage to collapse. Later, the dataset is divided into three traffic light damage tags: green, yellow, and red. The performance of the ML model to classify the building's damage into three damage tags is found better than that of classifying it into five damage categories. This research aims to be beneficial in planning and decision-making for emergency response and recovery following an earthquake. [ABSTRACT FROM AUTHOR]

The sliding base (SB) technique is an efficient and economical approach to mitigating seismic damage of low-rise buildings in rural areas. Based on the previous work on single-story SB structures, this study investigates the earthquake forces acting on multistory SB structures. Response history analyses of SB structures subjected to three-component earthquake excitations were performed. The computed results indicate that the increase in the number of stories tends to reduce the mean value of the peak base shear but has little influence on the coefficient of variation of the peak base shear. The peak story shears of a multistory SB structure subjected to an earthquake ground motion are reached at different time instants for different stories. The distributions of the equivalent lateral forces for SB structures with different story numbers follow the same trend, and the equivalent lateral forces tend to concentrate at the upper floors as the normalized peak ground acceleration and mass ratio increase. Simplified equations for computing the distribution of equivalent lateral forces were developed for design purposes. [ABSTRACT FROM AUTHOR]

As a famous deep and large fault in eastern China, the Tanlu Fault passes through Anhui, Jiangsu, and Shandong and into northeastern China. It is important to improve the understanding of seismic hazard assessments in areas near faults. We start a scenario earthquake simulation in the M7.5 earthquake potential area of the Xinyi-Sihong segment of the Tanlu Fault. The fault rupture length and width are constrained according to the scaling law of large intraplate earthquakes, the background normal stress is depth dependent, and the initial shear stresses are determined using trial and error by matching the earthquake magnitude. Considering the 120 km rupture length of the M7.5 earthquake, we compare the horizontal uniform stress model and self-similar stress perturbation model. Our findings reveal that the seismic source time function of the horizontal uniform stress model is similar to that of the Haskell model and that of the self-similar stress perturbation model is more similar to that of a real earthquake case. We compare the dynamic rupture simulation and ground motion results under four different stress conditions and find that the shorter the characteristic length of the self-similar function is, the rougher the initial stress. For the M7.5 earthquake with an epicenter in the vicinity of Suqian, the Xinyi-Tancheng segment, which is located in the IX-intensity zone north of the epicenter, vibrates more strongly on the northern side than on the southern side due to the influence of the low-velocity zone and the peak slip rate. The response spectra analysis at stations in the study area is useful for improving the earthquake resistance capability. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study carried out to develop a multi-severity casualty approach for predicting the number of fatalities and two levels of injuries resulting from an earthquake. The two levels of injuries are severity 1, which do not require hospitalization, and severity 2, which do require hospitalization. The method provides a probability distribution of casualty, which can assist policymakers and disaster management authorities in developing emergency response plans. The proposed approach takes into account two main sources of uncertainty: variations in ground motion values (by generating thousands of shaking maps considering the spatial correlation of intra-event uncertainty) and uncertainty in casualty rates (by using the fuzzy set theorem and random sampling). As a case study, the proposed method was applied to the Mosha fault seismic scenario (7.4 Mw) in Tehran, Iran. The results indicated that 200,300 people may lose their lives in that seismic scenario. Additionally, the number of injuries with severity 1 and severity 2 are estimated to be about 420,600 and 232,980, respectively. These numbers exceed the healthcare capacity in Tehran. The estimated number of fatalities was then compared with the results of some existing empirical models in the literature. This comparison revealed that the empirical models underestimate the number of fatalities due to various reasons, such as a lack of strong earthquakes in urban areas to be included in empirical models. Thus, the proposed approach has several advantages for estimating casualties in urban fabrics. [ABSTRACT FROM AUTHOR]

For regional hazard analysis or engineering applications, it is necessary to simulate a group of correlated ground motions containing information from given recordings. A new method is presented to conditionally generate ground motions at unobserved points using actual recordings in this localized region. This method is based on an extension of the traditional conditional simulation using a wavelet packet. Utilizing the advantages of wavelet-packet transformation, the time and frequency characteristics of ground motions are effectively identified. Besides by decomposing the signal into non-overlapping sub-frequency bands, it is possible to conditionally simulating stationary, space-time, and Gaussian random fields. These simulated motions are consistent with the actual recordings in terms of temporal variations in the frequency domain and its design spectrum, and their coherence functions satisfy the target coherence values. Two numerical examples have been provided to illustrate the capability of the proposed method: the simulation of ensembles of earthquake accelerograms using actual recordings and blind tests in SMART-1 array. [ABSTRACT FROM AUTHOR]

Earthquake early warning systems assess the size of an earthquake based on initial ground motion and provide warnings before the arrival of large waves. We employ the iterative regression to simultaneously estimate the station correlations and the corresponding linear relations for magnitude. We report the standard error reductions of the magnitude estimation based on the initial peak P-wave acceleration (${P_a}$ P a ), velocity (${P_v}$ P v ), and displacement (${P_d}$ P d ) as $14.52\% $ 14.52 % , $7.63\% $ 7.63 % , and $7.58\% $ 7.58 % , respectively. Factor analysis of the stationary correction reveals its correlation with several factors. This study shows that station correction can help to improve the precision of magnitude estimation in the future. [ABSTRACT FROM AUTHOR]

Irazú and Turrialba are a twin volcanic complex that marks a distinct stop in volcanism along the Central America volcanic arc. We present a new traveltime velocity model of the crust beneath Irazú and Turrialba volcanoes, Costa Rica, and interpret it considering the results of previous ambient noise tomographic inversions. Data were acquired by a temporary seismic network during a period of low activity of the Irazú–Turrialba volcanic complex in 2018–2019. Beneath the Irazú volcano, we observe low P -wave velocities (V P = 5 km s−1) and low velocity ratios (V P/ V S = 1.6). In contrast, below the Turrialba volcano, we observe low S -wave velocities (V S = 3 km s−1) and a high V P/ V S (= 1.85) anomaly. We found that locations of low V P and V S anomalies (−15 %) correspond well with shear wave velocity anomalies retrieved from ambient noise tomography. At shallower depths, we observe high V P and V S anomalies (+15 %) located between the summits of the volcanoes. Subvertical velocity anomalies are also observed at greater depths, with high V P and V S anomalies appearing at the lower limits of our models. We propose a complex structure of an intermediate magmatic reservoir, presenting multiphase fluid states of a liquid-to-gas transition beneath Irazú and a juvenile store of magmatic fluid beneath Turrialba, while shallow fluid transport provides evidence of magmatic–hydrothermal interactions. [ABSTRACT FROM AUTHOR]

In recent decades, research on renewable energy has been boosted by the emerging awareness of energy security and climate change and their consequences, such as the global cost of adapting to the climate impacts. Both onshore and offshore wind turbine farms have been considered as one of the main alternatives to fossil fuels. Their development currently involves seismic-prone areas, such as the Californian coastline and East Asia, where the risk of soil liquefaction is significant. Onshore wind turbines (OWTs) typically are founded on shallow rafts. Their operation can be affected strongly by the simultaneous presence of intense earthquakes and wind thrust, which may cause remarkable permanent tilting and loss of serviceability. In these conditions, accurate evaluation of the seismic performance of these structures requires the development of well-validated numerical tools capable of capturing the cyclic soil behavior and the build-up and contextual dissipation of seismic-induced pore-water pressures. In this paper, a numerical model developed in OpenSees, calibrated against the results of dynamic centrifuge tests, was used to evaluate the influence of some ground motion intensity Measures of the seismic behavior of OWTs included the amplitude, frequency content, strong-motion duration, and Arias intensity (energy content) of the earthquake, together with the effect of a coseismal wind thrust, which is not well explored in the literature. The seismic performance of an OWT was assessed in terms of peak and permanent settlement and tilting, the latter of which was compared with the threshold of 0.5° typically adopted in practice. [ABSTRACT FROM AUTHOR]

The double-couple model of the earthquake source has been proven remarkably successful in explaining the radiation pattern in the low-frequency wavefield. However, the radiation pattern is distorted in the high-frequency wavefield. The frequency dependence of the radiation pattern is often interpreted as the path effects. The impact of earthquake sources on radiation patterns is uncertain. In our study, based on the fact that P waves vibrate along the radial direction and S waves vibrate along the transverse direction, the path effects modified model of radiation pattern is proposed based on the optimal ratio coefficient by measuring radial-to-transverse spectral ratios at multiple frequency ranges. Then, we found that the correlation coefficient decreases with the increase of frequency but remains stable with the increase of distance. This means the complexity of the earthquake source can distort the wavefield at higher frequencies and drive variability in the ground motion. [ABSTRACT FROM AUTHOR]

An optimisation-based calibration technique, using the area metric, is applied to determine the input parameters of a stochastic earthquake-waveform simulation method. The calibration algorithm updates a model prior, specifically an estimate of a region's seismological (source, path and site) parameters, typically developed using waveform data, or existing models, from a wide range of sources. In the absence of calibration, this can result in overestimates of a target region's ground motion variability, and in some cases, introduce biases. The proposed method simultaneously attains optimum estimates of median, range and distribution (uncertainty) of these seismological parameters, and resultant ground motions, for a specific target region, through calibration of physically constrained parametric models to local ground motion data. We apply the method to Italy, a region of moderate seismicity, using response spectra recorded in the European Strong Motion (ESM) dataset. As a prior, we utilise independent seismological models developed using strong motion data across a wider European context. The calibration obtains values of each seismological parameter considered (such as, but not limited to, quality factor, geometrical spreading and stress drop), to develop a suite of optimal parameters for locally adjusted stochastic ground motion simulation. We consider both the epistemic and aleatory variability associated with the calibration process. We were able to reduce the area metric (misfit) value by up to 88% for the simulations using updated parameters, compared to the initial prior. This framework for the calibration and updating of seismological models can help achieve robust and transparent regionally adjusted estimates of ground motion, and to consider epistemic uncertainty through correlated parameters. [ABSTRACT FROM AUTHOR]

Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 × 10–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings. [ABSTRACT FROM AUTHOR]

The regional seismic risk assessment plays an important role in the disaster prevention and mitigation. The accurate time-history analysis for a region provides an important data base for regional seismic risk assessment. However, an accurate calculation method is limited, then, its accuracy still lacks validation. Meanwhile, there is also a lack of risk assessment methods and indicators applicable to the regional accurate time-history analysis, both of which hinder the seismic risk assessment. In this paper, a regional-scale time history analysis-driven method is proposed for the quantitative evaluation of regional seismic damage risk and verified with a real earthquake damage survey. First, the regional time history analysis method is introduced, including the automatic modeling, response calculating, result analysis and 3-D visualization modules. Second, a calculation method for seismic damage degrees (DD) of buildings is introduced. Subsequently, the probabilistic models of each DD under the ground motions with a specific intensity are calculated based on regional-scale nonlinear time history analysis. Next, the concept of the three-level seismic damage risk is offered, then a determining workflow of seismic damage risks is proposed based on the code-abiding three-level design requirement. Afterward, the regional seismic damage index is suggested for the quantitative evaluation of earthquake-induced damage risk. Finally, the actual seismic damage database of 192 buildings in epicenter of Ludian Earthquake is established through on-site investigations, then used to verify the regional simulation's accuracy. Consequently, it could be an aid to accurately present seismic damage distribution assessments and effectively develop seismic risk mitigation strategies. [ABSTRACT FROM AUTHOR]

This paper investigates the inelastic displacement ratios (IDRs) and displacement ductility demands of a wide range of single-degree-of-freedom (SDOF) systems subjected to pulse-like ground motions (GMs) of the 2023 Pazarcık (Kahramanmaraş) earthquake. A set of twenty-seven GMs characterized as pulse-like are utilized in the study. As-recorded velocity time histories of horizontal components are rotated over 90° at a step of 1° to attain the waveform with the largest peak ground velocity (PGV) over all horizontal orientations. Inelastic displacement ratio and displacement ductility spectra are computed through nonlinear response history analysis (RHA). Local amplifications of both spectra are observed at some periods. The results of this study show that large inelastic displacement and ductility demands are imposed on certain reinforced concrete (RC) structures. Finally, predictive models of the mean inelastic displacement ratio and mean ductility demand spectra (DDS) are developed based on the Gauss–Newton algorithm (GNA). The model provides a strong correlation between the computed and the estimated data, and sufficient convergence criteria. The results of this study collectively emphasize the necessity of integrating pulse-like GMs into future revisions of earthquake codes. [ABSTRACT FROM AUTHOR]

This study focuses on evaluating the performance of an aged heritage building made of unreinforced brick masonry under seismic conditions, both with and without retrofitting. To achieve this, an experimental examination was conducted using a scaled-down model of a single-story unreinforced building, constructed on a shake table at a 1:4 geometric scale. The responses of this model were recorded at the roof level, primarily in the form of displacements. Subsequently, the same scaled model was replicated in SAP2000 finite element (FE) software. The results obtained from the FE model closely matched the experimental findings, validating the computational approach. Following this validation, an existing masonry heritage school building situated at Aligarh Muslim University, Aligarh, was chosen for further investigation. In this subsequent analysis, natural frequencies and mode shapes were computed through model analysis, revealing closely spaced natural frequencies. To assess the seismic performance of the heritage building, a nonlinear time history analysis was conducted using actual ground motion data from the Koyna earthquake. The maximum compressive and tensile stresses generated numerically under both gravity and earthquake loading conditions were compared with permissible stresses in accordance with Indian masonry standard codes. The finite element model demonstrated that the building remains structurally sound under gravity loading, although some vulnerable areas were identified under earthquake loading conditions. To mitigate the stresses in these vulnerable zones, various retrofitting techniques were explored. Notably, the application of steel flats on floors and walls, along with GFRP sheeting, proved to be an effective solution, reducing stress levels by up to 90%. [ABSTRACT FROM AUTHOR]

Geometric complexities play an important role in the nucleation, propagation, and termination of strike-slip earthquake ruptures. The 2021 Mw7.4 Maduo earthquake rupture initiated at a large releasing stepover with a complex fault intersection. In the epicentral region, we conducted detailed mapping and classification of the surface ruptures and slip measurements associated with the earthquake, combining high-resolution uncrewed aerial vehicle (UAV) images and optical image correlation with field investigations. Our findings indicate that the coseismic ruptures present discontinuous patterns mixed with numerous lateral spreadings due to strong ground shaking. The discontinuous surface ruptures are uncharacteristic in slip to account for the large and clear displacements of offset landforms in the epicentral region. Within the releasing stepovers, the deformation zone revealed from the optical image correlation map indicates that a fault may cut diagonally across the pull-apart basin at depth. The left-lateral horizontal coseismic displacements from field measurements are typically ≤0.6 m, significantly lower than the 1–2.7 m measured from the optical image correlation map. Such a discrepancy indicates a significant proportion of off-fault deformation or the possibility that the rupture stopped at a shallow depth during its initiation phase instead of extending to the surface. The fault network and multi-fault junctions west and south of the epicenter suggest a possible complex path, which retarded the westward propagation at the initial phase of rupture growth. A hampered initiation might enhance the seismic ground motion and the complex ground deformation features at the surface, including widespread shaking-related fissures. [ABSTRACT FROM AUTHOR]

One of the most widely used linear techniques for solving damage identification problems and prediction of the system dynamic behavior is modal testing and analysis. However, most of real structures exhibit nonlinear behavior during their lifetime caused by a number of various reasons. The presence of nonlinearity in a structural system changes its dynamic characteristics; hence, the use of linear techniques is improper for prediction of the system behavior. In this paper, a vibration-based nonlinearity identification technique was proposed to identify early changes in a dynamic system prior to significant damages. This technique combines the time series Autoregressive Moving Average with Exogenous Inputs (ARMAX) modelling, probability theory, and Fuzzy C-Means (FCM) clustering algorithm to categorize the linear and nonlinear dynamic behaviors of a dynamic system. The technique aims to categorize the linear and nonlinear behaviors of a structure, when it is subjected to various levels of excitation source. To show the validity of the proposed method, a series of shake table tests was performed on a six-span steel truss bridge model. The bridge model was excited using different amplitudes of ground motion to control the nonlinearity degree of rubber-based supports. It can be concluded from the analysis results that the new vibration-based nonlinearity identification technique was able to identify nonlinear behavior of the bridge model once it was subjected to different levels of earthquake excitations. This algorithm was able to categorize the linear and nonlinear behaviors of the bridge model and define a specific threshold for different excitation sources. [ABSTRACT FROM AUTHOR]

Estimating the story drift directly from acceleration records is challenging. This paper presents a systematic integration scheme involving the empirical mode decomposition of signals to estimate the earthquake-induced displacement of buildings, including their permanent deformation after an earthquake. A three-phase algorithm is proposed. In phase-1, the displacement waveform without residual displacement is estimated, then in phase-2 the residual deformation is calculated. Combining both phase-1 and phase-2, the displacement waveform is estimated. Three types of acceleration data, namely, shaking table test data, seismic response data for a building, and near-fault ground motion data, were used to validate the proposed method. [ABSTRACT FROM AUTHOR]

The bidirectional ductile end diaphragm concept uses energy-dissipating buckling restrained braces (BRB) as fuses located at the end of a bridge superstructure's floating spans. This system using BRBs can provide seismic resilient and damage-free bridges fully operational immediately after an earthquake. A shake-table testing program was conducted to subject a 1/2.5-scale specimen to series of ground motions. The specimen tested represents one span of a five-span bridge having BRBs connected to the abutment and the pier next to it. The purpose of these tests was to experimentally validate proposed connection details when subjected to the three-dimensional (3D) displacement histories (compared with the axis of the BRBs) that resulted from bidirectional ground motions and the fact that the connections must accommodate inclined BRB layouts. The test protocol included earthquake displacement histories that represent design demands, cycles of thermal excitations, and (to eventually make the BRBs fail) extreme motions. The testing program validated the effectiveness of the proposed concept and the ability of BRBs to sustain multiple ground motions before failure. [ABSTRACT FROM AUTHOR]

The 1 January 2024 Noto-Hanto (Noto Peninsula) earthquake (MJMA 7.6) generated strong ground motion, large crustal deformation and tsunamis that caused significant damage in the region. Around Noto Peninsula, both offshore submarine and partially inland active faults have been identified by previous projects: Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and Japan Sea Earthquake and Tsunami Research Project (JSPJ). We inverted the tsunami waveforms recorded on 6 wave gauges and 12 tide gauges around Sea of Japan and the GNSS data recorded at 53 stations in Noto Peninsula to estimate the slip amount and seismic moment on each of active faults. The results show that the 2024 coseismic slips were 3.5 m, 3.2 m, and 3.2 m on subfaults NT4, NT5 and NT6 of the JSPJ model, located on the northern coast of Noto Peninsula and dipping toward southeast. A smaller slip, 1.0 m, estimated on NT8 on the southwestern end of the 2024 rupture, may be attributed to its previous rupture during the 2007 Noto earthquake. The total length of these four faults is ~ 100 km, and the seismic moment is 1.90 × 1020 Nm (Mw = 7.5). Almost no slip was estimated on the northeastern subfaults NT2 and NT3, which dip northwestward, opposite to NT4–NT5–NT6, and western subfault NT8. Aftershocks including the MJMA 6.1 event occurred in the NT2–NT3 region, but they are smaller than the potential magnitude (Mw 7.1) those faults can release in a tsunamigenic earthquake. Similar features are also found for the MLIT model; the 2024 slip was only on F43 along the northern coast of Noto Peninsula, and northeastern F42 did not rupture, leaving potential for future event. [ABSTRACT FROM AUTHOR]

This technical report explains details on the results of the investigation to build a subsurface structural model and a selection of earthquake data at the target site of the blind prediction exercise for "The 6th International Association of Seismology and Physics of the Earth's Interior/International Association of Earthquake Engineering International Symposium on the Effect of Surface Geology on Seismic Motion (ESG6)." The selection process of the target site in the Kumamoto Plain, Japan, in ESG6 was explained with a historical review of the blind prediction tests in the previous ESG conferences. We have collected existing subsurface structural and earthquake data and conducted geophysical and geotechnical surveys in and around the target site to generate important velocity structure and the earthquake data used in the blind test. Microtremor data were obtained in triangular arrays ranging in side lengths from 1 to 962 m, and active surface wave data were derived along a 36-m line at the site. These data were provided for the prediction of a subsurface structural model in the first step of the blind prediction exercise. We also conducted a velocity logging in a borehole to a bottom depth of 39 m at the site and laboratory tests of soil samples from the borehole. We constructed a velocity profile of the shallow and deep sedimentary layers from a combination of the geophysical and geotechnical data at the site, and validated it by comparing the characteristics of the ground motion data from the moderate event. This "preferred velocity model" was provided as a standard model to the participants in the second and third steps of the blind prediction test to predict the earthquake ground motions of a moderate event and the mainshock of the 2016 Kumamoto earthquake. [ABSTRACT FROM AUTHOR]

To reasonably evaluate the overall seismic performance of infilled wall frames, a corresponding nonlinear analysis model is constructed with infilled wall frames as the research object. It quantifies the failure levels of structural and non-structural components and proposes a method for extracting structural overall performance indicators. The vulnerability of the case frame structure is analyzed using the Incremental Dynamic Analysis (IDA) method. The results showed that the seismic performance of the infilled wall frame and the ordinary frame met the seismic fortification requirements, and the seismic capacity of the infilled wall frame was better. After implementing a 7-degree seismic fortification, the cumulative probability of basic integrity, minor damage, and moderate damage for infill wall frames reached 99.15 %, surpassing the fortification target of 1.5 g. However, the seismic capacity of ordinary frames was overestimated, as their cumulative probability of basic intact, minor damage, and moderate damage under a 7-degree seismic fortification was 99.7 %. Neglecting its impact, ordinary frames exhibited lower seismic performance compared to other structures, with a basic intact probability of only 48.49 % under frequent earthquake actions at 7 degrees. The research utilizes effective methods for evaluating the seismic vulnerability of infilled wall frames. [ABSTRACT FROM AUTHOR]

Two adjacent groundwater wells on the North China Platform are used to study how earthquakes impacted aquifers. We use the response of water level to solid Earth tides to document changes after earthquakes and how aquifer and fracture properties recovered to pre‐earthquake properties. We consider two models for the phase and amplitude of water level response to the lunar diurnal (O1) and semidiurnal (M2) tides: a leaky aquifer model, and a model in which fracture orientation determines the response. In the leaky aquifer model, changes arise from changes in permeability and storage; in the fracture model, changes are due to changes in apparent orientation of transmissive fractures. Responses in one well are best explained by the leaky aquifer model, and can explain the large amplitude coseismic water level and permeability changes and the non‐recoverable changes after the largest earthquake. Responses in the other well are consistent with the fracture model and show little coseismic change in water level but changes in apparent fracture orientation. Larger ground motions lead to larger coseismic water level changes and longer recovery times. We propose that the well in the more permeable and shallow aquifer has less variable pore‐pressures around the well. Larger coseismic strains from water level changes may enable longer‐lasting changes in aquifer properties. We conclude that relatively high permeability aquifers are less susceptible to impacts from seismic waves, and thus have small changes in water levels and hydrogeological properties. Plain Language Summary: After large earthquakes, the properties of aquifers can change, leading to changes in water levels in wells. We study changes in water levels that we attribute to changes in the properties of fractures or the permeabilities of aquifers that connect to the wells. We do so by monitoring how deformation caused by tides leads to changes in water levels in two wells. The deeper well in a less permeable formation has larger changes. The larger the ground motion from earthquakes and the larger the amplitude of the coseismic water level changes, the more likely and larger the changes in permeabilities. The larger the changes, the slower the recovery to pre‐earthquake properties. The shallower well in a more permeable formation has smaller changes and no long‐term changes in water level and hydrogeological properties, which we attribute to more uniform pore‐pressures around the well. Key Points: high permeability aquifers are less susceptible to disruption by seismic waveshydraulic property changes depend on the amplitude and frequency of ground motionlarger water level changes accompany larger changes in fracture orientation and irreversible changes in aquifer properties [ABSTRACT FROM AUTHOR]

The structure of a high-speed railway (HSR) bridge with a track system is complex, and the computational efficiency of seismic analysis for a refine HSR bridge with a track system model (BM) is low. This study considers an HSR bridge with CRTS II slab ballastless track system as a case study and develops a simplified model (SM) based on a method for simulating track constraints with equivalent springs. To obtain the optimal equivalent springs stiffness of SM, a finite element structural parameters updating framework utilizing an improved genetic algorithm is established, and the updated SM's dynamic characteristics and seismic response are compared to BM's. In addition, it uses SM to analyze the over-limit state and applicability of the bridge structural essential components. The results indicated that the model simplification ratio of SM reaches 95%. The seismic response results of SM and BM accurately agree with an average relative error of 3% and a maximum relative error of less than 5%. The over-limit state of the structure seismic response tends to be stable as the number of ground motion samples increases. The shear and bending capacity of the pier and the deformation of the fixed support have a high over-limit risk under longitudinal seismic, which is worth noting in the engineering design. [ABSTRACT FROM AUTHOR]

Seismic site effects (topography, geology, internal fracture, et al.) and direction amplification are an important component in inducing a landslide during an earthquake. The evaluation of the dynamic response characteristics of a slope is the first and important step in earthquake engineering design and regional hazard assessment. To document the seismic response of an irregular slope, broadband seismic field monitoring seismometers were deployed along an earthquake-induced landslide Mogangling slope, on the one of important water systems in Sichuan, Dadu River. Field monitoring data reveal that ground motion is directionally amplified near 80° clockwise from North parallel to slope inclination when the frequency is between 3 and 4 Hz, at the crest of the Mogangling slope. During an earthquake, the peak ground acceleration of the M1 station (slope crest) is 5.3 times greater than the M3 station (near slope toe). The standard spectral ratio (SSR) of the slope crest/slope toe (M1/M3) reaches a value of 11.5 at 1.4 Hz, during the earthquake. A series of discrete element numerical models indicate that SSR of the field monitoring data can be reproduced considering the irregular geometry, surficial weak layer, and internal fractures. The recent Luding earthquake on 5 September 2022 with a magnitude of Ms 6.8 induced slope failure in the Mogangling slope reveals the seismic amplification effect again. Our findings can offer some important insights into the mechanism of earthquake-induced landslide and regional-scale landslide distribution. [ABSTRACT FROM AUTHOR]

Earthquake-induced plane failure is typically generated on bedding rock slopes. This failure mode has been widely observed in the past earthquakes in Western China (e.g., Wenchuan earthquake). Among them, the multi-slip plane failure may occur with the presence of multiple bedding planes or internal discontinuities within the slopes. This study developed an extended Newmark sliding block model to investigate the multi-slip seismic displacements of the bedding rock slopes. The unified formulation is presented for seismic sliding analysis of bedding rock slopes with arbitrary numbers and inclinations of bedding planes. Both horizontal and vertical earthquake ground motions and the possible amplifications that may result from site and topographic effects are considered. The developed model is validated by the results from shaking table test. The multi-slip mechanism and the effects of dip angle of bedding planes and vertical ground motion are investigated. The results show that (1) the multi-slip failure evolution is different to that identified from the traditional method, indicating the significant interactions among the seismic sliding behavior associated with bedding planes. (2) The influence of the vertical component of ground motion on the multi-sliding displacement is within a range of 20%. (3) The dip angle of sliding planes has a large effect on the sliding displacement, even if the yield coefficient remains the same. Finally, the proposed method is used to evaluate the seismic displacement and performance of the Liujiawan landslide that was triggered in Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

The stochastic response of multi-story buildings isolated by laminated rubber bearing (LRB), lead-rubber bearing (N-Z system), friction pendulum system (FPS), and resilient-friction base isolator (R-FBI) is investigated under the independent multi-hazard scenario of earthquake ground motion (EQGM), wind load (WL), and blast-induced ground motion (BIGM), which are considered as uncertain inputs. A polynomial regression-based Monte Carlo simulation (PRBMCS) is proposed to enable computationally efficient fragility assessment of base-isolated buildings. The suitability of the PRBMCS for stochastic assessment of the base-isolated buildings is compared with the conventional Monte Carlo simulation (MCS), response surface method (RSM) and Cloud analysis. The fragility curves obtained using the PRBMCS are in good agreement with that of the MCS relatively. The study includes: the effects of the characteristic parameters of the four base isolators on the fragility of the base-isolated buildings under the three hazards; influence of the extent of uncertainty in the excitations; and comparison of fragilities of the base-isolated and fixed-base buildings. Notably, the influences of characteristic parameters of the isolators on the fragility of the base-isolated buildings are different under the three hazards. The differences in the stochastic behaviour under the different hazards could have contradictory influences on the selection of isolation parameters. [ABSTRACT FROM AUTHOR]

Using the three component acceleration records of the National Strong Motion Observation Network System (NSMONS) and the National Seismic Intensity Rapid Reporting and Earthquake Early Warning Network, the ground motion attenuation characteristics, spatial distribution, source rupture direction, and near-fault pulse characteristics of the Luding MS6.8 earthquake were analyzed. Comparing the observed values of peak ground acceleration (PGA), peak ground velocity (PGV), pseudo-spectral acceleration (PSA), and 90% significant duration (SD) with several typical ground motion prediction equations (GMPE), it was found that the ground motion attenuation characteristics of this earthquake are consistent with GMPE for the southwest region, but overall lower than the global model average level. In the comparison of between-event residuals, this earthquake exhibits different characteristics from the same magnitude thrust type earthquake. The within-event residuals reflect that the anelastic attenuation in the Luding region is slightly weaker than that in the Menyuan region. In terms of spatial distribution of ground motion parameters, the PGV and PSA with a period of 1.0 to 8.0 s have significantly higher intensity in the southeast direction of the epicenter than in other directions. Based on PGV, it is speculated that the source rupture direction of the earthquake was 151°, which is close to the fault strike of 163°. Pulse-like ground motions were identified in up to 12 sets of near-fault records with pulse periods significantly lower than historical earthquakes of similar magnitudes. Stations with pulse peak values greater than 40 cm·s−1 in the pulse dominant direction of the velocity time history all appeared in the narrow band area ahead of the rupture direction. The distribution area of near-fault pulses is highly correlated with the distribution of high macroseismic intensity areas and landslide areas, and it is necessary to pay attention to the impact of near-fault pulses in seismic fortification. [ABSTRACT FROM AUTHOR]

Near-source κ s , along-path κ ~ , and near-site κ 0 contributions to the spectral parameter kappa (κ ) were studied from earthquakes located along the Canal de Ballenas-Guaymas fault system and recorded by stations sited around the central-north Gulf of California, Mexico. The dataset consists of 26 earthquakes (M 3.4-6.0) recorded by six stations with hypocentral distances ranging from 31 to 270 km. We used the Anderson and Hough (1984) approach to estimate κ , followed by a one-step least-squares inversion to separate κ contributions. We found that κ has a range of 0.0260 to 0.1012 s, with a mean of 0.0600 ± 0.0170 s, while κ s and κ 0 exhibit means of 0.0088 ± 0.0059 s and 0.0200 ± 0.0205 s, respectively. We also observed significant inter-event κ s and inter-station κ 0 variabilities. The d κ ~ / d r regional average is 0.00023 ± 0.00001 s, equivalent to a regional quality factor of 1242 ± 54 for an S-wave velocity of 3.5 km/s. Furthermore, our results suggest that d κ ~ / d r tends to decrease with distance. We demonstrate that a well-designed least-squares inversion scheme can effectively address the limitations associated with estimating κ 0 using the Anderson and Hough approach in situations where recordings per station have a narrow distance range and where no recordings at small source-site distances are available for most stations. We found no correlation of κ s with earthquake magnitude. Instead, relatively higher κ s values tend to cluster along the ridge flanks of the Canal de Ballenas Basin, where hydrothermal fluid circulation is expected. [ABSTRACT FROM AUTHOR]

The energy content of ground motion records obtained during the 2019 M6.4, M7.1 Ridgecrest, California earthquakes which occurred closely in space is analyzed in this paper. Wavelet transform as a powerful tool, that is used to evaluate the energy content characteristics including cumulative energy profiles and the total energy for different components of records, was obtained at three stations named China Lake Christmas Canyon, China Lake and Tower 2. Due to the fact that the energy-based parameters could be well correlated with damage distribution, this path has been taken into consideration in this research work with the light of the powerful wavelet tool. For this purpose, the discrete wavelet transform is efficiently used for multi-resolution decomposition of acceleration time history of ground motions and a new framework is presented to estimate the energy level of earthquake sequences. Finally, the pseudo-period corresponding to each corresponding level is introduced and the distribution of energy vs. the pseudo-period is discussed. The results of this paper provide a platform to compare the energy levels of different earthquake sequences in different periods. Analysis showed that wide-band energy distribution could be identified at China Lake Christmas Canyon and Tower 2 stations. [ABSTRACT FROM AUTHOR]

Earthquake-induced landslide, a cascading hazard in hilly regions, can substantially increase the damaging effects of an earthquake. This necessitates performance evaluation of buildings situated in hilly regions under the effects of landslide-only and landslides following earthquakes. In this study, the performance of two commonly observed hillside building configurations is assessed—namely, step-back and split foundation—subjected to the above-mentioned multi-hazard scenarios using an uncoupled approach. The uncertainty in the soil properties that influence the landslide-induced forces is considered based on laboratory tests of soil samples collected from active landslide sites and an existing database of landslide events. Three-dimensional hillside buildings are analysed for uphill-side landslide scenarios by performing force-controlled non-linear static analyses. Further, a suite of earthquake ground motions is scaled to a predefined intensity level, and then non-linear time history analyses are performed to obtain the damaged state of the buildings prior to assessing the landslide response. It is observed that the earthquake loading history and its direction of excitation significantly affect the response of hillside buildings to a landslide following an earthquake. Further, the step-back building is observed to be more vulnerable to landslide damage when compared to its split foundation counterpart for a given uphill-side landslide scenario. [ABSTRACT FROM AUTHOR]

Rapid changes in geotechnical and geological ground conditions lead to significant ground motion variability. This condition mainly occurs at the so-called basin edges, where there is an abrupt transition between soft highly compressible soils and stiffer materials. This problem becomes more relevant in areas where ground subsidence drastically changes the dynamic response of high plasticity clay deposits, such as those found in Mexico City, due to fundamental site period evolution with time. This paper presents site response analyses at an abrupt transition area in the southeast Mexico City region, along the edges of the Xochimilco-Chalco lakes. Considerable damage associated with three-dimensional wave propagation effects was observed in this zone during the September 2017 Puebla-Mexico earthquake. A series of three-dimensional finite difference numerical models of the basin edge were developed to evaluate ground motion variability, considering topographic effects and soil non-linearities. Good agreement between the computed response and the observed damage during the 2017 Puebla-Mexico earthquake reconnaissance was found. In addition, several normal and subduction events with a return period of 250 years were considered to evaluate the effect that frequency content, and strong ground motion duration have on the soil response variability. From the results gathered here, it was established the relevance of accounting for three-dimensional wave propagation fields to assess site effects at basin-edge zones properly and to be able to implement proper risk mitigation measurements at these zones. [ABSTRACT FROM AUTHOR]

In this paper a novel approach named Multi Pier Macro MPM method is proposed for seismic analysis of steel moment frames. Based on the model an arbitrary multi-bay and multi-story moment frame is substituted by a single bay braced frame consists of two piers and two braces at each story. Piers are continuous and braces are pinned to piers. Both piers and braces are 1D truss elements. The axial, flexural and shear stiffness of the moment frame are provided by axial behavior of piers and braces. MPM method was benchmarked against four steel moment frames including two mid-rise and two high-rise buildings. The seismic responses of equivalent braced frames including maximum floor displacements and story drifts was compared with original moment frames responses as exact results, by means of Non-linear Static Procedure NSP and Non-linear Response History Analysis NL-RHA. NL-RHA was performed using twelve ground motion records scaled to Maximum Design Earthquake MDE and Maximum Considered Earthquake MCE hazard intensities. The results proved the simplified braced frame is able to estimate the seismic responses of mid and high-rise moment frame buildings with high accuracy meanwhile the analysis time and computational cost were limited remarkably. [ABSTRACT FROM AUTHOR]

This article presents a set of ground-motion prediction equations (GMPEs) for shallow crustal and upper mantle earthquakes in Japan with site period TS (four times the travel time of shear-waves vertically propagated down to the bedrock) as site parameter using a strong-motion dataset from Japan for shallow crustal and upper mantle earthquakes. We used a two-segmented magnitude-scaling function for the source effect, a set of simple geometric attenuation functions for the path effect, and a simplified transfer function of a single degree of freedom oscillator for the site period resonant effect. Because boreholes at some K-NET stations did not reach the bedrock within 20 m, we separated K-NET sites into two groups, with one group having reached bedrock, referred to as GE760 sites, and the others referred to as LT760 sites. We used the apparent site periods calculated using the borehole depth for LT760 sites and derived a GMPE for all sites. Using the between-site residuals, we estimated the site period shortfall, ∆TS, for each LT760 site and obtained the site periods accounting for the soil layers between the borehole depth and the possible bedrock depth. The modified site period equals the apparent site period plus the ∆TS for the LT760 sites. We developed a TS model using the new site period and achieved a significant increase in the maximum log-likelihood at spectral periods over 0.3 s. The TS model produces a continuous and smoothly varying response spectrum versus site period and has a smaller variability for long-period sites at long spectral periods. We compared the model predictions and model standard deviations from this study to a few other GMPEs for shallow crustal earthquakes, and the differences in the predictions among these GMPEs are considerable. [ABSTRACT FROM AUTHOR]

On May 21, 2021, at 21:48 local time, an earthquake with a moment magnitude of 6.1 occurred in Yangbi County, Yunnan Province, China. By using the robust strong ground motion data released by the Yunnan Earthquake Agency, we selected five near-field stations (R < 100 km) and determined model parameters, such as the duration, spectral attenuation, stress drop, and site amplification factors of the 2021 Mw 6.1 Yangbi earthquake in China. These model parameters required for the simulation were fed into a stochastic finite-fault model of the corner frequency associated with a dislocation. The modified stochastic finite-fault method was applied to simulate the acceleration recordings of these five near-fault stations, and the acceleration response spectra and Fourier acceleration spectrum were obtained. Comparative observation results reveal that the key input parameters extracted from a few stations and the revised approach established in the current study can adequately predict the near-fault ground motion at high frequencies of the Yangbi earthquake and can demonstrate the contribution of areas with large slips to radiated energy. The proposed method can provide a basis for postdisaster rescue and seismic building design for this region. [ABSTRACT FROM AUTHOR]

The offshore Campos Basin, located in Southeastern Brazil represents an important area in the Brazilian economy as it is one of the most prolific oil-producing basins in the country. With the development of offshore infrastructures in this region, structural design and location must consider different geohazards. This paper addresses the seismic response of gentle submarine slopes subjected to small-to-moderate-sized earthquakes, representative of the Brazilian seismic conditions. The seismic analyses employed numerical modeling, with a nonlinear constitutive model. A set of bedrock ground motions representative of the offshore Campos Basin seismicity was obtained, employing a Uniform Hazard Response spectrum for the region and earthquakes from the Pacific Earthquake Engineering Research (PEER) database. Numerical modelling results showed that, even for small slope angles and moderate earthquakes, there is an accumulation of permanent displacements and shear strains in the downslope direction can affect the stability and performance of existing offshore infrastructures. The findings of this research provide a valuable reference for the prediction of seismic displacements, shear strains and seabed amplification or attenuation of earthquakes on gentle slopes in deep-water deposits similar to those found in the offshore Campos Basin. [ABSTRACT FROM AUTHOR]

In 2023, two consecutive earthquakes exceeding a magnitude of 7 occurred in Türkiye, causing severe casualties and economic losses. The damage to critical urban infrastructure and building structures, including highways, railroads, and water supply pipelines, was particularly severe in areas where these structures intersected the seismogenic fault. Critical infrastructure projects that traverse active faults are susceptible to the influence of fault movement, pulse velocity, and ground motions. In this study, we used a unique approach to analyze the acceleration records obtained from the seismic station array (9 strong ground motion stations) located along the East Anatolian Fault (the seismogenic fault of the MW7.8 mainshock of the 2023 Türkiye earthquake doublet). The acceleration records were filtered and integrated to obtain the velocity and displacement time histories. We used the results of an on-site investigation, jointly conducted by China Earthquake Administration and Türkiye's AFAD, to analyze the distribution of PGA, PGV, and PGD recorded by the strong motion array of the East Anatolian Fault. We found that the maximum horizontal PGA in this earthquake was 3.0 g, and the maximum co-seismic surface displacement caused by the East Anatolian Fault rupture was 6.50 m. As the fault rupture propagated southwest, the velocity pulse caused by the directional effect of the rupture increased gradually, with the maximum PGA reaching 162.3 cm/s. We also discussed the seismic safety of critical infrastructure projects traversing active faults, using two case studies of water supply pipelines in Türkiye that were damaged by earthquakes. We used a three-dimensional finite element model of the PE (polyethylene) water pipeline at the Islahiye State Hospital and fault displacement observations obtained through on-site investigation to analyze pipeline failure mechanisms. We further investigated the effect of the fault-crossing angle on seismic safety of a pipeline, based on our analysis and the failure performance of the large-diameter Thames Water pipeline during the 1999 Kocaeli earthquake. The seismic method of buried pipelines crossing the fault was summarized. [ABSTRACT FROM AUTHOR]

We developed a modified stochastic finite-fault method for estimating strong ground motions. An adjustment to the dynamic corner frequency was introduced, which accounted for the effect of the location of the subfault relative to the hypocenter and rupture propagation direction, to account for the influence of the rupture propagation direction on the subfault dynamic corner frequency. By comparing the peak ground acceleration (PGA), pseudo-absolute response spectra acceleration (PSA, damping ratio of 5%), and duration, the results of the modified and existing methods were compared, demonstrating that our proposed adjustment to the dynamic corner frequency can accurately reflect the rupture directivity effect. We applied our modified method to simulate near-field strong motions within 150 km of the 2008 MW7.9 Wenchuan earthquake rupture. Our modified method performed well over a broad period range, particularly at 0.04-4 s. The total deviations of the stochastic finite-fault method (EXSIM) and the modified EXSIM were 0.167 6 and 0.149 4, respectively. The modified method can effectively account for the influence of the rupture propagation direction and provide more realistic ground motion estimations for earthquake disaster mitigation. [ABSTRACT FROM AUTHOR]

This study investigates the nonlinear seismic response behavior of self-centering modular steel bracing panel (SCMBP) systems subjected to near-fault ground motion records, considering the soil-structure interaction (SSI) effect. Analytical formulas for the load-displacement relationship of an SCMBP were validated through nonlinear 3D continuum finite element analysis while a simplified 2D wireframe model utilizing a constitutive spring model was verified by the 2D refined finite element model and subsequently adopted for time history analysis of the SCMBP structures with SSI effect. Based on the nonlinear time history analysis of a 6-story prototype building subjected to a suite of near-fault ground motions, the prototype structure is found to be able to re-center itself even under near-fault ground motion scaled to the design basis earthquake (DBE) level while frame members remain undamaged, except for fuse devices. Additionally, SSI reduces inter-story drift ratios under both far-field and near-fault ground motions. The findings provide insights into the promising performance of using SCMBP systems as a seismic strengthening system for sites with potential SSI effects and near-fault earthquake impact. The findings of this study can be insightful to other self-centering systems with flag-shaped story shear hysteresis. [ABSTRACT FROM AUTHOR]

This study aims to obtain the viable parameters of base isolation systems that are utilized in buildings with seismic isolation and specially located in Turkey. To provide a more accurate representation of real-world scenarios, the study accounts for severe ground motion records simultaneously during the dynamic response analysis of the structure. Three records are taken from the 2023 Turkey earthquake (records for Elbistan, Nurdagi, and Pazarcik). The optimization model's objective function is to minimize the ratio of the roof acceleration to the peak ground acceleration. To ensure realistic outcomes, certain isolation parameters are constrained, such as maintaining the damping ratio and period within a predetermined range as well as the maximum lateral drift of the structure. An upgraded variant of the Butterfly Optimization Algorithm, known as the Fuzzy Butterfly Optimization Algorithm (FBOA), is employed to address the presented optimization model. The FBOA technique incorporates a fuzzy decision-making mechanism that adjusts its search strategy according to the prevailing conditions of the present problem. In addition, the FBOA method utilizes a new auxiliary vector called virtual butterfly, which provides information on the entire population based on each agent's quality. Consequently, FBOA transforms into a self-regulating search algorithm, eliminating the requirement for any external parameters. Results have verified the effectiveness of FBOA in detecting optimal parameters of the proposed isolation system. [ABSTRACT FROM AUTHOR]

Due to the unique soil, morphological, and subsurface topographical conditions, amplified and prolonged seismic demand traces were observed in historical strong ground motion records from Bayrakli-Izmir-Turkiye. A vivid example of this response was recorded during the Mw 7.0 Samos event on October 30, 2020. After the event, structural damage and loss of life were unexpectedly concentrated in Bayrakli-Izmir, even though the fault rupture was located 70 km away. The presence of strong ground motion stations (SGMS) located on rock (#3514) and soil (#3513) sites enabled a quantitative assessment of the amplified and prolonged seismic demand traces. The seismic response of SGMS #3513 site was assessed by using 1-D equivalent linear and analytical methods. The idealized 1-D soil profile and input parameters were calibrated and fine-tuned by using the 2020 Samos earthquake accelerograms. Then, the calibrated equivalent linear site response model was further validated by the recordings from historical events. Alternatively, an analytical wave propagation-based model was proposed, the input parameters of which were probabilistically estimated based on, again, historical recordings. Finally, the seismic responses of the site during future earthquakes were predicted based on the calibrated and validated site response models. The predicted intensity-dependent amplification spectral responses were compared with the provisions of the TEC (2018). Even though limited in number in all five future seismic scenario events, amplification ratios suggested by TEC were exceeded by a factor of 2–4 at periods falling in the range of 0.5 to 1.2 s. This clearly suggested the need to further quantify the Bayrakli seismic basin responses with basin-specific models, rather than code-based, intensity-dependent generalized amplification factors. [ABSTRACT FROM AUTHOR]

Free-standing archaeological walls are significantly exposed to horizontal actions (e.g., earthquakes) as they lack connections provided by floors or roofs. In such cases, the dynamic response governs the activation of local mechanisms of collapse, determining the shape of the macroblocks and their position. Engineering models of archaeological walls are developed according to the results of extensive visual inspections and on-site testing, including modal identification for calibration purposes. A modal response spectrum analysis on the calibrated model identifies the zones where the tensile stress is exceeded, which are more likely to detach as rigid macroblocks and subsequently overturn due to the expected ground spectra. The macroblocks are then assessed according to limit analysis. The case studies are the north and the apse walls of the church of San Giovanni Evangelista in Castelseprio (Varese, Lombardy), a 5th century Longobard fortified settlement, a part of UNESCO World Heritage. The construction quality of the apse was poorer than the north wall, but the masonry of both is very compact thanks to the good mortar. The macroblocks are identified mostly in the upper crests of the walls, and their acceleration of activation is two to six times larger than the demand (considering the dynamic amplification that the structure applies to the ground motion); therefore, no particular intervention is needed. The proposed method will require additional calibration, e.g., through nonlinear dynamic analyses, and a more precise treatment of uncertainties in masonry mechanical properties to determine the shape of the macroblocks. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) using existing optical fiber cables facilitates high‐density seismic observation. However, few studies have examined the reliability of the seismic waveform amplitude recorded by DAS. In this study, a DAS network was connected to optical fiber cables installed over a distance of 75 km along a high‐speed train (Shinkansen) railway in the Kumamoto prefecture, Japan. We successfully observed strong motions of the Mj6.6 earthquake (approximately 150 km from the fiber) on 22 January 2022, in Hyuga‐nada, in addition to several small local earthquakes. The observed strong motions from the Mj6.6 earthquake, using DAS, exhibited cycle skipping (clipping) issues due to dynamic range limitations at numerous channels. To address this, we estimated the shaking map, representing maximum strain distributions for Mj6.6, by replacing the clipped data with information from nearby unclipped channels and scaling their RMS amplitudes based on S‐coda (unclipped). Furthermore, we verified the reliability of the amplitude information obtained from DAS by estimating the distance attenuation of seismic waves while correcting for the differences in the structure type and coupling as much as possible. The distance attenuation property of local earthquakes was consistent with that of the peak ground velocities obtained from seismometers, indicating that DAS data acquired using fibers installed on infrastructure (various structures) can also be utilized to assess the spatial distribution of the relative amplitude values along the fiber. Obtaining high‐density seismic motion distributions is important for earthquake early warning and accurate damage estimation of strong motions. Plain Language Summary: In the past decade, the use of distributed acoustic sensing (DAS) for seismological purposes has grown rapidly. By utilizing existing dark fibers, such as telecommunication cables, high‐density seismic observation networks can be established in residential areas. In this study, DAS was applied to an existing optical fiber cable installed along a railway line, which recorded strong ground motions of Mj6.6 originating from a subduction zone, as well as numerous regional earthquakes. Although the technique uses optical phase differences for strain measurements and therefore has a poor response to strong ground motions, we resolve this issue using the correct data from neighboring stations as a reference and estimated the shaking distribution every 5 m along 75 km of the railway line. Additionally, when we analyzed the distance attenuation of small regional earthquakes, we found that the attenuation characteristics were similar to those obtained from permanent seismometers. These findings will significantly impact society in the future, particularly as the fiber cables replace conventional seismic observation networks. As a result, ultra‐high‐density observation networks will be capable of issuing more accurate earthquake early warnings and estimating damage following earthquakes. Key Points: We successfully observed strong motion from the Mj6.6 earthquake in Hyuga‐nada using Distributed acoustic sensing (DAS) over 75 km along railwayThe shaking map of the Mj6.6 was estimated by replacing the clipped channels with nearby unclipped channels and scaling their RMS amplitudes of S‐codaDistance attenuation property of local earthquakes of DAS consistent with that of peak ground velocities from continuous seismometers [ABSTRACT FROM AUTHOR]

We use sparse dictionary learning to develop transformations between seismic velocity models of different resolution and spatial extent. Starting with data in the common region of both models, the method can enhance a regional lower‐resolution model to match the style and resolution of local higher‐resolution results while preserving its regional coverage. The method is demonstrated by applying it to two‐dimensional VS and three‐dimensional VP and VS regional and local velocity models in southern California. The enhanced reconstructed regional results exhibit clear visual improvements, especially in the reconstructed VP/VS ratios, and better correlations with geological features. Moreover, the reconstructed regional VP, VS models outperform the original ones in comparison of simulated earthquake waveforms to observations. The improved fitting to observed waveforms extends beyond the domain of the overlapping region. The developed dictionary learning approach provides physically interpretable results and offers a powerful tool for additional applications of data enhancement in earth sciences. Plain Language Summary: Seismic velocity models are essential for many applications including derivation of earthquake properties, studies of tectonic processes, and analysis of earthquake ground motions. In various places there are velocity models of different spatial coverage and resolution. To benefit from the complementary strengths of such models, we develop a new method for enhancing regional velocity models of relatively low‐resolution with information contained in local higher‐resolution models. The method builds a transformation between different models in their common local region based on a sparse dictionary learning and then uses the transformation outside the common region. We apply the method to seismic velocity models in southern California and show that the enhanced regional P and S velocity models outperform the original models in fitting earthquake waveforms and also have better consistency with geological features. The method has a potential for enhancing other data sets in earth sciences. Key Points: We present a new method for merging multi‐scale velocity models with different resolutions and spatial coveragesWe reconstruct multi‐scale VP, VS regional seismic velocity models for southern CaliforniaValidation with waveform simulations shows that the reconstructed models outperform the original ones [ABSTRACT FROM AUTHOR]

Distributed Acoustic Sensing (DAS) is becoming a powerful tool for earthquake monitoring, providing continuous strain‐rate records of seismic events along fiber optic cables. However, the use of standard seismological techniques for earthquake source characterization requires the conversion of data in ground motion quantities. In this study we provide a new formulation for far‐field strain radiation emitted by a seismic rupture, which allows to directly analyze DAS data in their native physical quantity. This formulation naturally accounts for the complex directional sensitivity of the fiber to body waves and to the shallow layering beneath the cable. In this domain, we show that the spectral amplitude of the strain integral is related to the Fourier transform of the source time function, and its modeling allows to determine the source parameters. We demonstrate the validity of the technique on two case‐studies, where source parameters are consistent with estimates from standard seismic instruments in magnitude range 2.0–4.3. When analyzing events from a 1‐month DAS survey in Chile, moment‐corner frequency distribution shows scale invariant stress drop estimates, with an average of Δσ = (0.8 ± 0.6) MPa. Analysis of DAS data acquired in the Southern Apennines shows a dominance of the local attenuation that masks the effective corner frequency of the events. After estimating the local attenuation coefficient, we were able to retrieve the corner frequencies for the largest magnitude events in the catalog. Overall, this approach shows the capability of DAS technology to depict the characteristic scales of seismic sources and the released moment. Plain Language Summary: A new formulation for far‐field strain radiation from seismic ruptures is derived, leading to a direct interpretation of Distributed Acoustic Sensing (DAS) data to retrieve source properties (seismic moment and source size), via a spectral modeling. This approach is validated on real data recorded in two different tectonic environments, the Chilean margin and the southern Apennines, in Italy. Despite the unique directional sensitivity and peculiar signal characteristics, we demonstrated the high potential of DAS systems in characterizing the seismic ruptures over different space scales, with accuracy increased by redundancy of information from the very‐high spatial resolution in the recording of seismic waves. Key Points: A theoretical description of strain far field radiation from a seismic rupture is introducedSource parameters were evaluated from strain data for earthquakes in magnitude range 2.0–4.3Distributed Acoustic Sensing allows for investigation of source parameters and site effects with fine spatial resolution [ABSTRACT FROM AUTHOR]