Motion Recordings Research Articles

Ground Motion Duration Patterns for Vrancea (Romania) Intermediate-Depth Earthquakes

This study is focused on evaluating ground motion durations of Vrancea intermediate-depth earthquakes in Romania, in the context of future updates to the Romanian seismic design code P100-1/2013. The ground motion database compiled for this study consists of about 200 ground motions recorded during five moderate and large Vrancea intermediate-depth earthquakes that occurred in the period of 1977–2004 and had moment magnitudes of MW ≥ 6.0. Two empirical models were derived in this study for the significant ground motion duration considering two time intervals (5–75% and 5–95%) for the accumulation of the Arias Intensity IA. An analysis of the data shows that the mean ratio between D5-95 and D5-75 is about 2.8. Moreover, the regression also shows that the largest share of variability is due to the within-event component (site term). Among the regression coefficients, the hypocentral distance and the soil conditions appear to have a larger impact on the ground motion duration compared to the earthquake magnitude. It was also observed that the median ground motion durations predicted using the empirical model proposed in this study were much smaller than the ones from the proposed Eurocode 8 draft for the same magnitude range. Finally, geographic trends related to the distribution of residuals were also evaluated using the data from the three earthquakes with the largest number of available ground motion recordings.

Three-dimensional numerical modeling of ground motion in the Valley of Mexico: A case study from the Mw3.2 earthquake of July 17, 2019

In this study, a 3D physics-based numerical approach, based on the spectral element numerical code SPEED, is used to simulate seismic wave propagation due to a local earthquake in the Mexico City area. The availability of detailed geological, geophysical, geotechnical, and seismological data allowed for the creation of a large-scale (60 km × 60 km in plan, 10 km in depth) heterogeneous 3D numerical model of the Mexico City area, dimensioned to accurately propagate frequencies up to about 1.3 Hz. The results of numerical simulations are validated against the ground motion recordings of the July 17, 2019, Mw3.2 earthquake, with peak ground acceleration exceeding 0.3 g about 1 km away from the epicenter. A good agreement with records is found, quantitatively evaluated through goodness-of-fit checks. Furthermore, for the lake zone, the simulated decay trend of the peak ground velocity with epicentral distance is reasonably close to the observations, for both horizontal and vertical components. In spite of some limitations, the simulations are successful to provide a realistic picture of seismic wave propagation both in the hill and in the lake zones of Mexico City, including the onset of long-duration quasi-monochromatic ground motion in the basin, with strong amplification at low frequencies (between 0.4 and 0.7 Hz). The numerical results also suggest that surface waves, with predominant prograde particle motion at the ground surface and large ellipticities, dominate the wavefield in the lake zone. Based on these positive outcomes, we conclude that this numerical model may be useful for both a better insight into the seismic response of the Valley of Mexico and the simulation of ground motions during larger-magnitude earthquakes, to generate improved seismic damage scenarios in Mexico City.

The influence of seismic displacement models on spatial prediction of regional earthquake-induced landslides

Regional landslide prediction is a critical step towards achieving community resilience against landslides during earthquakes. We present a predictive methodology for regional earthquake-induced landslides that uses a pseudo-three-dimensional (pseudo-3D) procedure implemented on a digital elevation model (DEM). The methodology calculates a seismic displacement for every grid cell in the DEM as the basis for predicting the location and the size of landslide that is determined using a three-dimensional (3D) geometric projection based on topography. This “pseudo-3D” methodology for predicting landslides outperforms cell-based approaches. It has the advantage of deriving landslide number and size characteristics of individual landslides. We quantify the influence of seven commonly used seismic displacement models: four rigid, two decoupled flexible, and one fully coupled flexible. Seismic displacement model performance is evaluated by implementing a prediction for the 2015 Mw6.5 Lefkada earthquake event in Greece for which precise location and high-resolution landslide volume data are available for model validation and ground motion intensity measures are well constrained by nearby ground motion recordings. The 3D landslide inventory was created by topographically differencing pre-existing DEMs from post-event digital surface models derived from satellite and unmanned aerial vehicle (UAV) imagery. The inventory contains over 700 landslides, primarily shallow disrupted slides and rock slides, along with occasional occurrences of deep-seated, rotational failures. Qualitative comparisons between predicted and mapped landslides show that all seismic displacement models predict landslides that broadly overlap geospatially with most mapped landslides and the regions of high mapped landslide densities are predicted. A variety of metrics are used to quantify the prediction results: these include metrics such as landslide number and area density, as well as correctly predicted ratio, overlapped ratio, centroid distance, ground failure capture, and efficiency. The results show that the Rathje and Antonakos (kmax, k-velmax) model and the Saygili and Rathje (PGA, PGV) model correctly predict the most mapped landslides and obtain the highest prediction efficiency, but at the cost of the highest overprediction. The Bray and Macedo model achieves the best performance in predicting landslide number, area density, and location accuracy, but the correct prediction of the mapped landslides and the prediction efficiency are worse than other seismic displacement models. The results highlight the role of seismic displacement models in the prediction of regional earthquake-induced landslides and guide selection of the seismic displacement model depending on the objective of the prediction. Strength parameters also affect landslide prediction, and we demonstrate that all evaluation metrics vary widely due to variation of cohesion and friction angle, except for the correctly predicted ratio. More importantly, variation in prediction results due to the selection of seismic displacement models is found to be comparable to variation in results associated with strength parameter uncertainty. A critical slope parameter is proposed and defined as the flattest slope at which landslide triggering may occur for a given predictive model. As such, seismic displacement models that have lower critical slopes predict more landslides and differences in critical slopes for each seismic displacement model provide a parsimonious explanation for the different performances of the seismic displacement models in the regional earthquake-induced landslide prediction.

Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions.

In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.

Shake table tests on timber frame structure infilled with dry bond masonry

This study presents the results of a series of half-scale shake table experiments conducted on a single-room; single-story timber frame filled with dry-bonded brick masonry. Two half-scale models, one without infill and one infilled with dry bond brick masonry, were fabricated and tested on a shaking table to examine the seismic performance of timber-framed masonry structural systems. For dynamic characterization, both models were subjected to white noise base excitation, and to investigate the seismic behaviour, the models were subjected to incrementally increasing ground motion in accordance with single ground motion record incremental dynamic analysis. The dynamic characteristics, such as natural frequencies, damping, mode shapes, and stiffness degradation, were evaluated. The stiffness degraded to 43% in the model infilled with bricks and 62% in the model without infill. The peak acceleration and displacement responses and the global hysteresis response were assessed and evaluated. While determining the acceleration profiles of the model, the maximum out-of-plane acceleration recorded was of the order of 1.1 g for the model without infill and 1.6 g for the model with infill. The acceleration response was more amplified for models with brick infill, while a lower value was observed in models without infill. Based on the fact that the structure was linear even at maximum acceleration amplification during the test, it can be inferred that the timber-framed structure possesses a high degree of flexibility and deformability, and also that the energy dissipation capacity of the structure increased with the increase in peak ground acceleration of the input ground motion.

Hazard‐consistent simulated earthquake ground motions for PBEE applications on stiff soil and rock sites

AbstractGround motion record selection is a standard step in state‐of‐the‐art performance‐based earthquake engineering (PBEE) applications. It links the structural response to seismic hazard of the site of interest. In this process, suites of hazard‐consistent ground motion recordings of a wide range of intensity levels are selected (and often scaled) from a database of ground motions to be used as input to nonlinear dynamic response analysis. The ideal practice would be to select ground motions from a database of recorded accelerograms in such a way that they are consistent with the seismic hazard at as many intensity measure (IM) levels as possible and for all important causative scenarios. However, the available databases are not heavily populated, especially for the large‐magnitude short‐distance scenarios. Therefore, synthetic ground motions are the natural candidates to enlarge the database of recordings for scenarios that are important to the site hazard but lack, completely or partially, recorded accelerograms. The usage of such recordings, however, can be recommended only after they are proven to be “realistic” through a battery of seismological and statistical tests. In this study, we propose and implement a multi‐fold testing framework for such an evaluation. We first generate a ground motion database of simulated ground motions (SDB) whose values of the parameters of the causative earthquakes are, to the extent possible, the same of those that caused the ground motions in a mirror database of recorded ground motions (RDB). We then utilize the conditional spectrum (CS) approach computed for a hypothetical rock site in Perugia, Italy, to select hazard consistent records separately from the RDB and SDB databases. A comprehensive set of comparisons of distributions of several IMs, computed from the selected sets, and of distributions of engineering demand parameters (EDPs), that such record sets induce on simple SDoF structures suggests the adequacy of using the proposed simulated ground motions for structural response analyses of structures on stiff and rock sites.

Evaluating a Kinematic Data Glove with Pressure Sensors to Automatically Differentiate Free Motion from Product Manipulation

When studying hand kinematics, it is key to differentiate between free motion and manipulation. This differentiation can be achieved using pressure sensors or through visual analysis in the absence of sensors. Certain data gloves, such as the CyberGlove II, allow recording hand kinematics with good accuracy when properly calibrated. Other gloves, such as the Virtual Motion Glove 30 (VMG30), are also equipped with pressure sensors to detect object contact. The aim of this study is to perform a technical validation to evaluate the feasibility of using virtual reality gloves with pressure sensors such as the VMG30 for hand kinematics characterization during product manipulation, testing its accuracy for motion recording when compared with CyberGlove as well as its ability to differentiate between free motion and manipulation using its pressure sensors in comparison to visual analysis. Firstly, both data gloves were calibrated using a specific protocol developed by the research group. Then, the active ranges of motion of 16 hand joints angles were recorded in three participants using both gloves and compared using repeated measures ANOVAs. The detection capability of pressure sensors was compared to visual analysis in two participants while performing six tasks involving product manipulation. The results revealed that kinematic data recordings from the VMG30 were less accurate than those from the CyberGlove. Furthermore, the pressure sensors did not provide additional precision with respect to the visual analysis technique. In fact, several pressure sensors were rarely activated, and the distribution of pressure sensors within the glove was questioned. Current available gloves such as the VMG30 would require design improvements to fit the requirements for kinematics characterization during product manipulation. The pressure sensors should have higher sensitivity, the pressure sensor’s location should comprise the palm, glove fit should be improved, and its overall stiffness should be reduced.

Towards semi-automated pleural cavity access for pneumothorax in austere environments

Astronauts are at risk for pneumothorax, a condition where injury or disease introduces air between the chest wall and the lungs (i.e., the pleural cavity). In a worst-case scenario, it can rapidly lead to a fatality if left unmanaged and will require prompt treatment in situ if developed during spaceflight. Chest tube insertion is the definitive treatment for pneumothorax, but it requires a high level of skill and frequent practice for safe use. Physician astronauts may struggle to maintain this skill on medium- and long-duration exploration-class missions, and it is inappropriate for pure just-in-time learning or skill refreshment paradigms. This paper proposes semi-automating tool insertion to reduce the risk of complications in austere environments and describes preliminary experiments providing initial validation of an intelligent prototype system. Specifically, we showcase and analyse motion and force recordings from a sensorized percutaneous access needle inserted repeatedly into an ex vivo tissue phantom, along with relevant physiological data simultaneously recorded from the operator. When coupled with minimal just-in-time training and/or augmented reality guidance, the proposed system may enable non-expert operators to safely perform emergency chest tube insertion without the use of ground resources.

Condylar motion analysis: a controlled, blinded clinical study on the interindividual reproducibility of standardized evaluation of computer-recorded condylar movements

The present study investigated to what extent a systematic evaluation of electronic condylar motion recordings leads to reproducible results in different examiners. The study was based on the anonymized condylar motion recordings of 20 patients (Cadiax compact II system). These were recruited consecutively from the examinations in a center specializing in diagnosing and managing temporomandibular disorders (TMD). Four trained practitioners independently evaluated the identical movement recordings of all patients after calibration. The evaluation was based on the previously published evaluation system. The results were recorded digitally in a database. The findings were then compared, and the matching values were determined (Fleiss' Kappa). The evaluation, according to Fleiss' Kappa, showed that the consistency of the assessment of the findings among the examiners is excellent (mean value 0.88, p < 0.00001). The study shows that calibrated dentists achieved reproducible results using this evaluation system and computer-assisted reporting. Good reproducibility confirms the reliability of systematic evaluation of clinical motion analysis. The ambiguities uncovered and eliminated in the study should avoid misunderstandings in the future. Both factors establish the prerequisites for applying condylar motion analysis in clinical practice.

Ground motion emissions due to wind turbines: observations, acoustic coupling, and attenuation relationships

Abstract. Emissions from wind turbines (WT) cover a wide range of infrasound and ground motions. When they are perceived as immissions by local residents, they can become a source of disturbance or annoyance. To mitigate such disturbances, it is necessary to better understand and, if possible, suppress WT-induced emissions. Within the project Inter-Wind we record and analyze ground motion signals in the vicinity of two wind farms on the Swabian Alb in southern Germany, simultaneously with acoustic and meteorological measurements, as well as psychological surveys done by cooperating research groups. The investigated wind farms consist of 3 and 16 WTs, respectively, and are located on the Alb peneplain at 700–800 m height, approximately 300 m higher than the two municipalities considered in our study. Our main aim is to better understand reasons why residents may be affected from WT immissions. Known ground motions include vibrations due to eigenmodes of the WT tower and blades, and the interaction between the passing blade and the tower, causing signals at constant frequencies below 12 Hz. In addition, we observe signals in ground motion recordings at frequencies up to 90 Hz which are proportional to the blade-passing frequency. We can correlate these signals with acoustic recordings and estimate sound pressure to ground motion coupling transfer coefficients of 3–16.5 µms-1Pa-1. Sources for these emissions are the WT generator and possibly the gearing box. The identification of such noise sources can help to find measures to reduce disturbances in order to increase the public acceptance of WTs. Residents perceive more disturbance at the location where the wind farm is closer to the municipality (approximately 1 km). However, there is also a major railway line which produces higher vibration and infrasound signal amplitudes compared to the WTs. Along the measurement lines the decay rate of the WT-induced ground motions is determined for a damping relation proportional to 1/rb. We find frequency-dependent b values for different scenarios at our geological setting of Jurassic limestone on marl, sandstone, and Quaternary deposits. These damping relationships can be used to estimate emissions in the far field and to plan mitigation strategies.

Shaking table test and numerical analyses of a full scale three-leaf masonry wall

This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The applied loading protocol consisted of the horizontal component of a ground motion record that is repeatedly applied to the shaking table with increasing intensity. Finally, the main results of the experimental test are discussed. The damage patterns, drift ratios and base shear are presented for the ground motion sequence. The results are also discussed through a dynamic capacity curve that shows the attainment of different limit states with increasing ground motion intensity. A set of nonlinear numerical simulations, both static and dynamic, using a 3D FE model of the wall verify the experimental study as they report good agreement with the experimental tests and exhibit stable numerical behaviour.

Optimal Acceleration and Energy-Based Record Selection Using Artificial Intelligence Approaches and NP

ABSTRACT The new trend toward modern earthquake-resistant design of buildings based on nonlinear dynamic analysis accounting for peak and energy demands requires efficient ground motion record selection procedures. For this reason, in the present work, two record selection strategies based on acceleration and input energy spectrum considering the spectral shape via Np are presented. Furthermore, both record selection strategies are optimized by means of four artificial intelligence (AI) techniques: Genetic Algorithms (GA), Harmony Search (HS), Particle Swarm Optimization (PSO) and Vibrating Particle System (VPS). In particular, the effectiveness of each AI approach toward the best set of ground motion records for nonlinear dynamic analysis is compared. For this aim, spectral acceleration and input energy design spectra were considered, as well as 1024 seismic records obtained from the Pacific Earthquake Engineering Research Center. For all the AI or meta-heuristic approaches, the fitness function used is focused on minimizing the difference between the average spectrum of eleven ground motion records and the design spectrum using the well-known parameter Np, which represents the spectral shape in a range of periods. In addition, a penalization is included for those spectra with very large or low demands. Thus, 24 sets of eleven seismic records that can be used for nonlinear dynamic analysis of structures with a fundamental period of vibration of 0.6, 1.2 and 1.8 seconds were obtained and purposes. The results demonstrate the ability of the two records selection strategies analyzed and the four meta-heuristic procedures, achieving results quickly and simply regardless of the type of demands, intensities and periods considered. Finally, it is concluded that the VPS algorithm is better in comparison with GA, HS, and PSO since it obtains superior results in almost all the selected cases.

Broadband ground motion simulation using a hybrid approach of the May 21, 2021 M7.4 earthquake in Maduo, Qinghai, China

In this study, the broadband ground motions of the 2021 M7.4 Maduo earthquake were simulated to overcome the scarcity of ground motion recordings and the low resolution of macroseismic intensity map in sparsely populated high-altitude regions. The simulation was conducted with a hybrid methodology, combining a stochastic high-frequency simulation with a low-frequency ground motion simulation, from the regional 1-D velocity structure model and the Wang WM et al. (2022) source rupture model, respectively. We found that the three-component waveforms simulated for specific stations matched the waveforms recorded at those stations, in terms of amplitude, duration, and frequency content. The validation results demonstrate the ability of the hybrid simulation method to reproduce the main characteristics of the observed ground motions for the 2021 Maduo earthquake over a broad frequency range. Our simulations suggest that the official map of macroseismic intensity tends to overestimate shaking by one intensity unit. Comparisons of simulations with empirical ground motion models indicate generally good consistency between the simulated and empirically predicted intensity measures. The high-frequency components of ground motions were found to be more prominent, while the low-frequency components were not, which is unexpected for large earthquakes. Our simulations provide valuable insight into the effects of source complexity on the level and variability of the resulting ground motions. The acceleration and velocity time histories and corresponding response spectra were provided for selected representative sites where no records were available. The simulated results have important implications for evaluating the performance of engineering structures in the epicentral regions of this earthquake and for estimating seismic hazards in the Tibetan regions where no strong ground motion records are available for large earthquakes.

Investigation on Improved Optimal Fixed Time Step in Time-History Analysis for Aseismic Design of High-Speed Railway Bridge-Track System

ABSTRACT Time-history analysis is currently the main approach to the aseismic design of high-speed railway, and the time step significantly affects the calculation efficiency and accuracy. A 5-span high-speed railway bridge-track system was used as an example in this study. The effect of different fixed time steps on maximum seismic response was analyzed. An approach of improved optimal fixed time step was proposed by introducing maximum frequency and sampling frequency multiple. According to the research findings, for a specified ground motion record, the calculation error and efficiency of the improved fixed time step decrease with the increasing sampling frequency multiple. For a specified sampling frequency multiple, the calculation efficiency decreases with the increasing high-frequency components in ground motion record. The calculation error of secondary sampling signal for random ground motion records approximately obeys the normal distribution, and a stable and deterministic upper bound can be constructed based on the random sample of calculation error. The sampling frequency of secondary sampling signal in aseismic analysis for high-speed railway bridge-track system should be set as 4fmax. The improved optimal fixed time step should be set as (4fmax)−1 to simultaneously satisfy both the calculation error and efficiency requirements.

A closer look at hazard-consistent ground motion record selection for building-specific risk assessment: Effect of soil characteristics and accelerograms’ scaling

Conditional spectrum (CS) record selection is a standard tool for the selection of ground motion recordings consistent with the hazard at a site of interest. For many important applications the seismic hazard is computed for reference rock conditions and the effects of local site conditions are investigated downstream via soil dynamics. Ideally, when selecting for rock conditions, the recordings should be real, recorded on rock sites, and strong enough to push the structure into its severe nonlinear range. However, rock-recorded ground motions are often scarce and the analyst is usually left with the suboptimal option of augmenting the set with scaled motions and motions recorded at soil stations. We investigated how this practice can affect the structural response estimates by means of nonlinear dynamic analyses of a comprehensive set of single-degree-of-freedom (SDOF) systems. We first performed site and structure-specific CS record selection using ground motion databases of only soil-recorded motions versus databases of only rock recorded ones. In addition, we performed the CS based on extreme cases of using ground motions scaled by either only small or only large factors. Our focus was on the statistical comparison of the common intensity measures (IMs) of the selected records and, more importantly, of the structural response estimates when these extreme opposite selection choices are made. We show no significant statistical differences in the distributions of the IMs and structural responses, while the fragility and response hazard remain almost identical, for all practical purposes. These results imply that, as long as hazard consistency is accurately enforced in the ground motion record selection, using CS, selecting soil-recorded motions or record scaled up to 10, will not bias the response estimates. Finally, repeating the above procedure for response prediction of one multiple degrees of freedom (MDOF) system suggests that our conclusions are applicable also to more complex structural systems.

Non-smooth dynamic analysis of curved bridges considering the earthquake-induced end-pounding

Curved beam bridges are widely used to accommodate the needs of complex transportation networks. However, these bridges are characterized by a complex dynamic response under earthquake excitation, and it is common to observe pounding-induced damages at the interfaces between adjacent beams or between the beam and the abutment after high-intensity earthquakes. The identification of pounding occurrences is a challenging task and highly dependent on the computational strategy used. The present paper addresses this problem by proposing and analyzing the suitability of an innovative non-smooth approach to solve the rigid bodies’ dynamic response and contact interactions problem of curved beam bridges subjected to seismic ground motions. To this end, the dynamic equations of motions, including the pounding effects, are first formulated with the introduction of the Lagrange multipliers approach. The unilateral constraints are converted into a linear complementarity problem (LCP) formulation related to the velocity and impulse in the normal and transverse directions. The proposed algorithm of the differential equations in LCP form is successively implemented in Matlab to identify the collision and motion states by accessing the stepwise acceleration time history. A two-span curved beam bridge with an intermediate pier and two adjacent abutments under a single ground motion record is considered for case study purposes to investigate the suitability of the proposed procedure. The accuracy of the proposed method is verified by comparison with finite element (FE) analysis. The analysis results include the bridge’s displacement time history and the motion states of all observed pounding occurrences. Finally, three validation methods, including the LCP relationship, the geometric relationship, and the momentum theorem, are evaluated to examine the validity of the proposed method. The results show that the proposed non-smooth dynamic formulation represents a new rigorous approach to identify and analyze the complex problem of end-pounding occurrence in curved bridges.

Development of a bidirectional rocking isolation bearing system (Bi‐RIBS) to control excessive seismic response of bridge structures

AbstractA bidirectional rocking isolation bearing system (Bi‐RIBS) is proposed to provide seismic protection for bridge structures. By using the 3‐D rocking motion of the Bi‐RIBS, this system acts as a mechanical fuse to limit the maximum force transmitted to the bridge piers and as a restoring component to control an excessive girder response. Possible applications in bridge structures were discussed. A simple analytical model was established to characterize the dynamics of an example bridge featuring such a Bi‐RIBS. A series of dynamic analyses were performed by using the proposed model to investigate the effects of several factors on controlling the seismic responses of the bridge, for example, the design parameters of Bi‐RIBS including inclined angle and size, the damping property at the support interface, and the mass ratio. The peak ground accelerations of the bidirectional ground motion record were scaled to various levels to evaluate the maximum performance indices of the bridge structure and the response control effectiveness of the Bi‐RIBS compared to the uncontrolled counterparts. The simulation results demonstrated that the proposed Bi‐RIBS could effectively control the maximum pier displacement while keeping the bearing from overturning if suitable parameters were selected. In particular, the control effectiveness on the maximum pier response becomes more significant as the seismic intensity increases, due to its distinctive negative stiffness property.

Quantitative analysis of surface‐wave propagation in the Mexico City Valley

AbstractThe Mexico City basin is an extreme example of an alluvial geological structure that induces long duration and large amplification on ground motions. Researchers have established that the seismic wavefield within the Mexico City basin is composed primarily of surface waves. In the present work, we present a quantitative analysis of the surface‐wave field propagating in the Mexico City basin and generated by thrust‐ and normal‐faulting events. Surface waves are identified and extracted from three‐component ground motion recordings using a technique that exploits the polarization of ground motion. The spatial analysis of the extracted waves clearly shows that the basin response, is strongly dominated by low‐frequency ( to ) Love waves. For all seismic events considered, we found that the identified Love waves can reach amplitudes three times larger as compared to Rayleigh waves. Our analysis indicates that surface wave amplification (as defined in the present work) increases with the 1D fundamental resonant site‐period T1, and appears to be independent of earthquake magnitude. We also quantify the mean delay time of the central frequency f0 of the extracted waves. We found that the of Love waves is spatially more coherent as compared to that of Rayleigh waves. The parameter T1 appears to be a good “proxy” of surface wave effects. This is manifested by a reciprocal relation that was established between T1 and the frequency f0 of the extracted Love waves. Equally important, the latter reciprocal relation turns out to be independent of earthquake magnitude.

EESD special issue: AI and data‐driven methods in earthquake engineering – (Part 1)

EESD special issue: AI and data‐driven methods in earthquake engineering – (Part 1)

Sleep Apnea Detection by Tracheal Motion and Sound, and Oximetry via Application of Deep Neural Networks.

Sleep apnea (SA) is highly prevalent, but under diagnosed due to inaccessibility of sleep testing. To address this issue, portable devices for home sleep testing have been developed to provide convenience with reasonable accuracy in diagnosing SA. The objective of this study was to test the validity a novel portable sleep apnea testing device, BresoDX1, in SA diagnosis, via recording of trachea-sternal motion, tracheal sound and oximetry. Adults with a suspected sleep disorder were recruited to undergo in-laboratory polysomnography (PSG) and a simultaneous BresoDX1 recording. Data from BresoDX1 were collected and features related to breathing sounds, body motions and oximetry were extracted. A deep neural network (DNN) model was trained with 61-second epochs of the extracted features to detect apneas and hypopneas from which an apnea-hypopnea index (AHI) was calculated. The AHI estimated by BresoDX1 (AHIbreso) was compared to the AHI determined from PSG (AHIPSG) and the sensitivity and specificity of SA diagnosis were assessed at an AHIPSG ≥ 15. Two-hundred thirty-three participants (mean ± SD) 50 ± 16 years of age, with BMI of 29.8 ± 6.6 and AHI of 19.5 ± 22.7, were included. There was a strong relationship between AHIbreso and AHIPSG (r = 0.91, p < 0.001). SA detection for an AHIPSG ≥ 15 was highly sensitive (90.0%) and specific (85.9%). We conclude that the DNN model we developed via recording and analyses of trachea-sternal motion and sound along with oximetry provides an accurate estimate of the AHIPSG with high sensitivity and specificity. Therefore, BresoDX1 is a simple, convenient and accurate portable SA monitoring device that could be employed for home SA testing in the future.