Motion Recordings Research Articles

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.

Relational database for building strong motion recordings used for seismic impact assessments

Historical data play a primary role in reconstructing building seismic responses and assessing damage in near-real time. While these types of data sets exist, they are often fragmented, difficult to access, and require significant manual manipulation on the part of the user to obtain useful information. This article introduces a relational database that comprises historical data from 216 buildings subjected to [Formula: see text] earthquakes, spanning a 36-year period in California. It includes comprehensive information about the events and accelerometer-equipped buildings, parameters that are often used in post-earthquake impact assessments, and time-series structural response data recorded during real earthquakes. The database is designed to facilitate incremental updating as new events occur, and the associated data becomes available. It is also paired with a Python-based tool that reduces the barrier to user access with a few simple inputs. The long-term goal is to expand the database to include additional seismic events and spur the development of similar single- or multi-hazard repositories.

Application of metaheuristic algorithms in prediction of earthquake peak ground acceleration

AbstractThe seismic resilience of a structure has been evaluated using peak ground acceleration (PGA). Ground motion parameters such as source characteristics, local site conditions are used to forecast the PGA of the ground motion. This paper aims to develop an Artificial Neural Network (ANN) based model to predict the PGA. Here, hypocentral distance (), shear wave velocity (), and moment magnitude (), are used as input parameters. The model uses 12,706 ground motion recordings from 283 earthquakes from the revised NGA‐West2 database supplied by Pacific Engineering Research Centre. Among the whole data, 70% of the data is set for training, 15% for validation, and 15% for testing the network. The R value derived from the testing dataset is 0.952, indicating the excellent performance of a network. An extensive parametric study is conducted with the PGA values, and the results indicate that the PGA increases with the magnitude and decreases with the hypocentral distance. The predicted PGA values from the present study are comparable with those from the existing relationships in the global database. The generated ANN model is further verified by comparing the predicted and recorded PGA values of an actual recorded event.

Spectral acceleration basin amplification factors for interface Cascadia Subduction Zone earthquakes in Canada’s 2020 national seismic hazard model

Canada’s 2020 national seismic hazard model (CSHM 2020) provides hazard estimates for interface Cascadia Subduction Zone (CSZ) earthquakes in southwestern Canada using four ground motion models (GMMs) with equal weights. Two out of the four GMMs were derived using data primarily from subduction earthquakes in Japan so their use in CSHM 2020 includes a “Japan-to-Cascadia” factor to account for local site conditions. Despite this regional factor, the GMMs do not explicitly consider the amplification effects from the Georgia sedimentary basin below Metro Vancouver. This study benchmarks ground motion shaking from a suite of 30 physics-based simulations of M9 CSZ earthquakes, which explicitly account for basin effects for periods exceeding 1 s, to corresponding estimates from interface GMMs in CSHM 2020. Using this comparison, this study proposes site-specific and period-dependent basin amplification factors for a range of sites located within the Georgia sedimentary basin. The average basin amplification factors at the deepest basin location reach values as high as 2.24 and 6.29 at a 2 s period with respect to basin-edge and outside-basin reference locations, respectively. We evaluate the proposed factors by comparing them against long-period amplifications observed in empirical strong motion recordings from the 2001 M6.8 Nisqually earthquake. A framework to incorporate the proposed basin amplification factors in the calculation of CSHM 2020 uniform hazard spectra (UHS) is also proposed. The modified UHS ordinates at the deepest basin location reach values that are 58% to 271% higher, at a 2 s period, than non-basin UHS estimates when amplification factors are calculated with respect to basin-edge and outside-basin reference locations, respectively.

Near-Collapse Probability of RC Frames in Indonesia Under Repeated Earthquakes Containing Fling-Step Effect

The velocity pulse and displacement fling-step pulse signatures may be present in a near-field earthquake ground motion record. It is generally known that near-field ground motion with pulse effects accelerated the building drift. The damage of building can also occur as a result of two or three earthquakes within the building's lifespan. The repeated earthquakes could cause minor to severe damage to the building, including structural collapse. This includes earthquakes with fling-step pulse, which impact is underexamined in the existing studies. Therefore, the objective of this study is to assess the impact of repeated earthquakes with displacement of the fling-step pulse on the near-collapse probability of 5-, 10-, 15 and 20-story concrete frames. Based on the response modification factor R = 8, 5, and 3, the frames are classified as special, intermediate, and ordinary, respectively. The result shows that the near-collapse probability of repeated earthquakes is more likely to occur on the concrete frames which reaches intensity measure of 27.0% than the effect of single earthquakes.

Virtual reality set-up for studying vestibular function during head impulse test.

Virtual reality (VR) offers an ecological setting and the possibility of altered visual feedback during head movements useful for vestibular research and treatment of vestibular disorders. There is however no data quantifying vestibulo-ocular reflex (VOR) during head impulse test (HIT) in VR. The main objective of this study is to assess the feasibility and performance of eye and head movement measurements of healthy subjects in a VR environment during high velocity horizontal head rotation (VR-HIT) under a normal visual feedback condition. The secondary objective is to establish the feasibility of VR-HIT recordings in the same group of normal subjects but under altered visual feedback conditions. Twelve healthy subjects underwent video HIT using both a standard setup (vHIT) and VR-HIT. In VR, eye and head positions were recorded by using, respectively, an imbedded eye tracker and an infrared motion tracker. Subjects were tested under four conditions, one reproducing normal visual feedback and three simulating an altered gain or direction of visual feedback. During these three altered conditions the movement of the visual scene relative to the head movement was decreased in amplitude by 50% (half), was nullified (freeze) or was inverted in direction (inverse). Eye and head motion recording during normal visual feedback as well as during all 3 altered conditions was successful. There was no significant difference in VOR gain in VR-HIT between normal, half, freeze and inverse conditions. In the normal condition, VOR gain was significantly but slightly (by 3%) different for VR-HIT and vHIT. Duration and amplitude of head impulses were significantly greater in VR-HIT than in vHIT. In all three altered VR-HIT conditions, covert saccades were present in approximatively one out of four trials. Our VR setup allowed high quality recording of eye and head data during head impulse test under normal and altered visual feedback conditions. This setup could be used to investigate compensation mechanisms in vestibular hypofunction, to elicit adaptation of VOR in ecological settings or to allow objective evaluation of VR-based vestibular rehabilitation.

Erratum: Combining earthquake ground motion and ambient vibration recordings to evaluate a local high-resolution amplification model—Insight from the Lucerne area, Switzerland

An erratum on: Janusz P, Perron V, Knellwolf C and Fäh D (2022) Combining Earthquake Ground Motion and Ambient Vibration Recordings to Evaluate a Local High-Resolution Amplification Model—Insight From the Lucerne Area, Switzerland. Front. Earth Sci. 10:885724. doi: 10.3389/feart.2022.885724An omission to the funding section of the original article was made in error. The following sentence has been added: "Open access funding was provided by ETH Zurich".The original version of this article has been updated.

Nonlinear Seismic Assessment of Historical Masonry Karaz Bridge Under Different Ground Motion Records

The most significant artifacts that transfer the cultural heritage of past civilizations to the present are historical structures. Historical bridges are of great importance in terms of transportation, trade and architecture from past to present. Some of these structures have been destroyed by natural disasters or have suffered significant structural damage. Especially earthquakes cause damage to these structures. In this study, the earthquake behavior of the Historical Karaz Bridge was investigated. The structural elements of the bridge and the materials connecting the bearing elements were evaluated together with the macro modeling approach. For this purpose, a 3D finite element model of the bridge was generated and its seismic behavior under different ground motion records was investigated by nonlinear analysis. Analyzes were carried out using the ground motion records of Bingöl, Elazığ, Erzincan, Van and Gölcük, and the results were evaluated mutually. In the analysis results, the dynamic behavior of the bridge was evaluated over the distribution of displacements and stresses and the earthquake behavior was investigated.

A new system to measure the trunk angle and pelvis angle during wheelchair propulsion.

The number of wheelchair users is increasing as the population ages. However, there is still lack of tools to objectively assess posture during wheelchair propulsion. The purpose of this study was to develop a system to measure trunk and pelvis ROM (range of motion) while driving a wheelchair and to assess the reproducibility of the measured posture changes and cyclic fluctuations during propulsion. Motion recorders were attached to the sternum and pelvis of fifteen healthy adults, and a pressure sensor was attached to the right heel. Subjects drove a standard wheelchair using their right leg and trunk and pelvis ROM was measured in two separate sessions. To detect the trend of postural changes during propulsion, a trend curve was computed from the measured ROM using a low-pass filter and then subtracted from the measured ROM waveforms. The resulting curves were normalized and averaged, and the maximum, minimum, and amplitude of the cyclic variation during propulsion were assessed for reproducibility. Intraclass correlation coefficients of the maximum, minimum, and amplitude ranged from 0.65 to 0.84. The proposed method can estimate the posture change and the periodic fluctuation during wheelchair propulsion with high reproducibility.

Quantifying the effect of amplitude scaling of real ground motions based on structural responses of vertically irregular and regular RC frames

Increasing number of real ground motion (GM) record databases raised nonlinear dynamic analysis (NDA) as an attractive option to determine structural response statistics. Structural responses are sensitive to input motions and the appropriate selection and scaling of real GMs is one of the crucial topics in earthquake engineering. In this paper, the influence of amplitude scaling on important earthquake demand parameters (EDPs), namely, global drift ratio, inter-story drift ratio and maximum floor acceleration, were studied using different scaling approaches and scaling limits. Eurocode-8 was used as a reference seismic code and amplitude scaling effects on structural responses of vertically irregular and regular structures were quantified. Efficiency and sufficiency of amplitude scaling were assessed in terms of mean, dispersion and non-exceedance probability curves of the EDPs. Statistical distribution of GM characteristics and their dependence on GM amplitude scaling were also discussed. Evaluations have shown that similar mean responses can be obtained regardless of scaling limits, approaches, and building topology if spectral shape compatibility is ensured. Furthermore, results demonstrated that neither building regularity nor scaling of GMs influenced the statistical distribution of ground motion parameters and non-exceedance probability curves of the EDPs. In fact, it was revealed that record selection scenario including spectral compatibility of individual GMs had a dramatic impact on dispersion and exceedance probability of structural responses.

Heart ID: Biometric Identification Using Wearable MIMO RF Heart Sensors

Biometric identification (ID) has become increasingly prevalent in the digital era. Static biometric methods, such as fingerprint and facial recognition are widely accepted, yet generally vulnerable to targeted presentation attacks. Current development has expanded to dynamic biometrics, such as gait and electrocardiogram, that enable continuous authentication and are significantly more resistant to presentation attacks. However, dynamic biometrics often involve cumbersome acquisition which restricts their widespread use. Here, we introduce Heart ID, a novel dynamic biometric system that uses near-field coherent sensing (NCS) with a multiple-in multiple-out (MIMO) radio-frequency (RF) antenna setup to non-invasively acquire detailed recordings of internal cardiac dielectric boundary motion over clothing. NCS couples localized energy to the heart to derive interpersonal structural differences, while MIMO significantly increases the biometric entropy compared to single-point observation. We performed a human study of 20 subjects as well as 2 longitudinal evaluations, and employed an unsupervised feature extraction method to explore the ID performance of this new biometric. We found an ensemble classification approach using features derived from unsupervised learning can achieve accuracy exceeding 99% at a 40-second epoch.

A fast nonlinear dynamic analysis automated approach to produce fragility curves for 3D RC frames

This study describes an automated procedure to assess seismic fragility of 3D reinforced concrete frame structures. A number of 9600 3D nonlinear dynamic analyses are performed using the recently developed 3D Force Analogy Method, implemented in an automated Matlad-based non-commercial code. The numerical efficiency of 3D Force Analogy is first illustrated for a broad range of structures and groud motion recordings and scaling factors. The ground motion dataset consisting of 20 horizontal recordings used in the study is characteristic for soft deep soil sites (e.g Bucharest) which are affected by large magnitude earthquakes originating in the Vrancea intermediate-depth seismic source. A total of 24 RC frame structures, both regular and irregular are employed in the study. The Park-Ang damage index is employed in order to evaluate the damage states of the structures. Fragility functions corresponding to life-safety and collapse damage states are obtained for both principal directions of the structures. The results show similar median fragility values on both principal directions, and a larger variability on the transversal direction. The analyses have also shown that the standard deviations evaluated for the mean annual failure rates corresponding to the two considered damage states and on both principal directions is almost equal to the mean value. The mean value of the collapse probability evaluated for the peak ground acceleration with a mean return period of 2475 years and based on the results of all 24 models is 6.1 % for the longitudinal direction and 6.5 % for the transversal direction.

Assessment of the prediction of ground motion parameters in 1D ground response analysis using data from seismic arrays and centrifuge experiments

Peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration are among the most widely used metrics to represent seismic hazard characteristics in practice. Several simplified seismic design procedures to evaluate liquefaction triggering, slope stability, or structural response have also proposed other ground motion parameters (GMPs) to represent a ground motion’s intensity, duration, and frequency content. To account for soil effects, these parameters can be obtained from the results of one-dimensional (1D) ground response analyses. Few studies have systematically evaluated the prediction of these additional parameters from the results of ground response analyses. This study presents an exhaustive review of the accuracy and precision of the prediction of 19 common GMPs from the results of 1D ground response analyses using vertical seismic arrays and centrifuge tests. Total stress nonlinear analyses are conducted using the software DEEPSOIL along with equivalent-linear analysis. A reference dataset composed of 10 sites and 306 ground motion recordings representing varying conditions of seismic excitation is employed. The findings of this study showed that while the models produced a reasonable approximation of spectral accelerations, a general tendency toward the over-prediction of most parameters was revealed. The results identified that the mean period ( Tm) yielded the lowest bias, and other parameters, such as the predominant spectral period ( To), PGA, and PGV, also offered some improvements over the other parameters included in this study.

Distribution of strong input energy in base-isolated structures with complex nonlinearity: a parametric assessment

PurposeOver the past few decades, several base isolation systems have been developed to enhance the performance of structures under extreme earthquake shaking intensities. Recently, to achieve high energy dissipation capabilities, a new generation of multi-stage friction pendulum (FP) bearings known as the “Quintuple Friction Pendulum (QFP)” was introduced in the literature. With the help of its five effective pendula and nine operational regimes, this bearing's major benefits stem from its ability to accomplish complicated multi-stage adaptive behavior with smoothed loading and unloading when subjected to lateral forces.Design/methodology/approachWithin the assessment context, five finite element models of reinforced concrete frames supported on QFP isolators with different properties will be developed in OpenSees. Thereafter, a set of 60 earthquakes will be analyzed using the nonlinear time history analysis approach, and the impact of each ground motion record's properties will be evaluated.FindingsOverall, the study's findings have demonstrated that the characteristics of the isolator, combined with the type of earthquake being applied, have a substantial impact on the isolator's behavior.Originality/valueCurrently, no studies have examined the energy distribution of structural systems equipped with this type of isolation system while considering the influence of earthquake characteristics. Thus, this study is intended to extend the findings available in the literature by discussing and illustrating the distribution of strong ground motions input energy into highly nonlinear base-isolated systems that account for the bearing and superstructural materials' nonlinearity, geometric nonlinearity and leakage-prevented viscous damping nonlinearity. Besides, it investigates the influence of various earthquake characteristics on the energy dissipation of such buildings.

Sea trials of Sigma wave energy converter – slacking and snapping of TLP mooring lines

Sigma Energy has performed its foremost prototype tests of scaled wave energy converter in a real sea environment. The prototype was a point absorber with a cylindrical buoy, a mechanical power take-off system with a counterweight, moored to the seabed as a tension leg platform (TLP) with three equal tendons. In these extensive experiments, numerous device characteristics were measured and analysed. The present paper focuses on the dynamic forces in the mooring lines, and some unexpected and rare data obtained. It is well known that TLP tendons are prone to a brief loss of tension (the slacking) and that, after such events, high snapping forces of short duration can arise. Partly by intention, and partly due to underestimation of the dynamical forces, several such slacking-snapping incidents were recorded during the experiments. In some severe storms, the snapping forces were up to six times higher than the tendon pretension. The paper presents several recordings of dynamic forces and platform motion during these critical events. It analysis them, and gives a typical scenario under which they occur. It gives also some theoretical explanations, and numerical predictions of dynamical tendon forces, with their comparison to the experimental results.

Quantification of rupture directivity effects on strong ground motion during the 8 January 2022 MS6.9 Menyuan earthquake in Qinghai, China

On 8 January 2022, an MS6.9 earthquake occurred in the Menyuan county, Qinghai province at the northeastern margin of the Tibetan Plateau. A dense observatory network consisting of accelerographs and intensity meters has obtained many acceleration recordings in this region, which previously had only a few strong motion recordings. Using acceleration data recorded by 141 accelerographs and micro-electro mechanical system (MEMS)-based intensity meters within 100 km of the causative fault, we investigated the spatial distribution and attenuation characteristics of the near-source ground motion during this event. The observed response spectra were compared with the prediction obtained using the NGA-West2 models. It was found that, in the long-period section of &amp;gt;1.0 s, the acceleration response spectra in the rupture forward direction (southeast of the epicenter) were greater than the prediction, while observations on the northwest side were lower than the prediction. Through the spatial distribution of the ground motion and quantitative analysis of the residuals, we found that the rupture directivity effects on the ground motions were controlled by the spatial azimuth relative to the fault and the along-strike projected length of the rupture, which mainly affected the long-period portion of the &amp;gt;1.0 s. In the rupture forward direction, the spectral accelerations (SAs) with periods of 1.0–10.0 s were enhanced to 1.18–1.56 times the average. In the backward direction (northwest of the epicenter), the SAs with periods of 1.0–10.0 s were only 0.63–0.86 times the average. The rupture directivity effects during the MS6.9 (MW6.6) earthquake exhibited an obvious period-dependence and narrowband characteristics, and the amplification effects were the strongest at 5.0 s. The amplification factors in the straight forward directions were underestimated by the empirical model. Two typical velocity pulse records were observed in the rupture forward direction, and their response spectra were significantly amplified at long periods of greater than 1.0 s, with peak amplification values of 4.0–6.0 near the characteristic period of the pulses. This amplification was related to the resonance excited by a specific periodic pulse. Our study provides a reference of quantifying near-source effects for both moderate and major shallow crustal earthquakes by using MEMS recordings in this region.

Experimental Methods for Studying the Contact Mechanics of Joints.

Biomechanics researchers often experimentally measure static or fluctuating dynamic contact forces, areas, and stresses at the interface of natural and artificial joints, including the shoulders, elbows, hips, and knees. This information helps explain joint contact mechanics, as well as mechanisms that may contribute to disease, damage, and degradation. Currently, the most common in vitro experimental technique involves a thin pressure-sensitive film inserted into the joint space; but, the film's finite thickness disturbs the joint's ordinary articulation. Similarly, the most common in vivo experimental technique uses video recording of 3D limb motion combined with dynamic analysis of a 3D link-segment model to calculate joint contact force, but this does not provide joint contact area or stress distribution. Moreover, many researchers may be unaware of older or newer alternative techniques that may be more suitable for their particular research application. Thus, this article surveys over 50 years of English-language scientific literature in order to (a) describe the basic working principles, advantages, and disadvantages of each technique, (b) examine the trends among the studies and methods, and (c) make recommendations for future directions. This article will hopefully inform biomechanics investigators about various in vitro and in vivo experimental methods for studying the contact mechanics of joints.

Quantification of amplitude modulation of wind turbine emissions from acoustic and ground motion recordings

Amplitude modulation (AM) is a common phenomenon associated with wind turbine (WT) related noise annoyance. Within the interdisciplinary project Inter-Wind, acoustic, ground motion, and meteorological data are captured to be evaluated with noise reports of residents living near a wind farm in Southern Germany. The recorded data builds a solid data base for the evaluation of AM. The occurrence of AM is detected within acoustic and ground motion data and set in relation to all available data, including WT operational parameters, meteorology, and noise reports. In this study, the origins of detected AM are tones at 57.8 Hz and 133 Hz, related to the generator and drive train, which are amplitude modulated by the blade passing frequency. AM detection was successful both with acoustic as well as ground motion data. A comparison of a method for AM detection developed by the Institute of Acoustics (IOA reference method) with a method specifically developed to detect AM in ground motion data showed that the reference method detected AM three to six times more often than the newly developed method. AM occurred most likely during stable atmospheric conditions, with a positive lapse rate, and was (albeit to a small degree) more likely to be detected when residents reported higher levels of annoyance.

A database of ground motion recordings, site profiles, and amplification factors from the Groningen gas field in the Netherlands

A comprehensive database that has been used to develop ground motion models for induced earthquakes in the Groningen gas field is provided in a freely accessible online repository. The database includes more than 8500 processed ground motion recordings from 87 earthquakes of local magnitude ML between 1.8 and 3.6, obtained from a large network of surface accelerographs and borehole geophones placed at 50 m depth intervals to a depth of 200 m. The 5%-damped pseudo-acceleration spectra and Fourier amplitude spectra of the records are also provided. Measured shear-wave velocity (VS) profiles, obtained primarily from seismic Cone Penetration Tests (CPTs), are provided for 80 of the ∼100 recording stations. A model representing the regional dynamic soil properties is presented for the entire gas field plus a 5 km onshore buffer zone, specifying lithology, VS, and damping for all layers above the reference baserock horizon located at about 800 m depth. Transfer functions and frequency-dependent amplification factors from the reference rock horizon to the surface for the locations of the recording stations are also included. The database provides a valuable resource for further refinement of induced seismic hazard and risk modeling in Groningen as well as for generic research in site response of thick, soft soil deposits and the characteristics of ground motions from small-magnitude, shallow-focus induced earthquakes.