Earthquake Shaking Research Articles

Online jointly estimation of hysteretic structures using the combination of central difference Kalman filter and Robbins–Monro technique

Rapid assessment of structural safety and performance right after the occurrence of significant earthquake shaking is crucial for building owners and decision-makers to make informed risk management decisions. Hence, it is vital to develop online and pseudo-online health monitoring methods to quantify the health of the building right after significant earthquake shaking. Many Bayesian inference–based methods have been developed in the past which allow the users to estimate the unknown states and parameters. However, one of the most challenging part of the Bayesian inference–based methods is the determination of the parameter noise covariance matrix. It is especially difficult when the number of unknown states and parameters is large. In this study, an effective online joint estimation method for nonlinear hysteretic structures, with consideration of degradation and pinching phenomena, is proposed. Simultaneous estimation of states and parameters is conducted using the combination of a central difference Kalman filter as an effective estimator and the Robbins–Monro stochastic approximation technique as the parameters noise covariance matrix regulator. The proposed algorithm is implemented on three shear buildings with 36, 54, and 90 unknown states and parameters. To verify the performance of the system identification method, robust simulations with synthetic measurement noises and modeling errors were generated using the Monte Carlo random simulation method. The result shows the proposed method can be used to estimate the unknown parameters and states of highly nonlinear systems efficiently and effectively.

Stochastic seismic slope stability assessment using polynomial chaos expansions combined with relevance vector machine

This paper presents probabilistic assessment of seismically-induced slope displacements considering uncertainties of seismic ground motions and soil properties. A stochastic ground motion model representing both the temporal and spectral non-stationarity of earthquake shakings and a three-dimensional rotational failure mechanism are integrated to assess Newmark-type slope displacements. A new probabilistic approach that incorporates machine learning in metamodeling technique is proposed, by combining relevance vector machine with polynomial chaos expansions (RVM-PCE). Compared with other PCE methods, the proposed RVM-PCE is shown to be more effective in estimating failure probabilities. The sensitivity and relative influence of each random input parameter to the slope displacements are discussed. Finally, the fragility curves for slope displacements are established for site-specific soil conditions and earthquake hazard levels. The results indicate that the slope displacement is more sensitive to the intensities and strong shaking durations of seismic ground motions than the frequency contents, and a critical Arias intensity that leads to the maximum annual failure probabilities can be identified by the proposed approach.

Practical limitations of earthquake early warning

Earthquake early warning (EEW) entails detection of initial earthquake shaking and rapid estimation and notification to users prior to imminent, stronger shaking. EEW (ShakeAlert Phase 1, version 2.0) went operational in California in October 2019 and is coming to the rest of the U.S. West Coast. But what are the technical and social challenges to delivering actionable information on earthquake shaking before it arrives? Although there will be tangible benefits, there are also limitations. Basic seismological principles, alert communication challenges, and potential response actions, as well as substantial lessons learned from the use of EEW in Japan, point to more limited opportunities to warn and protect than perhaps many expect. This is in part because potential warning times vary by region and are influenced by tectonic environment, hypocentral depth, and the fault’s proximity to the alert user. For the U.S. West Coast, particularly for crustal earthquakes, warning times are shorter—and possible mitigation actions are likely to be less effective—than often maintained. Nevertheless, EEW is an additional arrow in the quiver of earthquake information tools available in the service of earthquake risk reduction. What is called for, then, is transparency and balance in the EEW discussion: along with its potential, the acknowledgment of EEW’s inherent and practical limitations is needed. Recognizing these limitations could, in fact, make EEW implementation more successful as part of a holistic earthquake mitigation strategy, where its role among other earthquake information tools is quite natural.

Design and implementation of a mobile device app for network-based earthquake early warning systems (EEWSs): application to the PRESTo EEWS in southern Italy

Abstract. A fundamental feature of any earthquake early warning system is the ability of rapidly broadcast earthquake information to reach a wide audience of potential end users and stakeholders, in an intuitive, customizable way. Smartphones and other mobile devices are nowadays continuously connected to the Internet and represent the ideal tools for earthquake alerts dissemination to inform a large number of users about the potential damaging shaking of an impending earthquake. Here we present a mobile app (named ISNet EWApp or simply EWApp) for Android devices which can receive the alerts generated by a network-based Early Warning system. Specifically, the app receives the earthquake alerts generated by the PRESTo EEWS, which is currently running on the accelerometric stations of the Irpinia Seismic Network (ISNet) in southern Italy. In the absence of alerts, EWApp displays the standard bulletin of seismic events that have occurred within the network. In the event of a relevant earthquake, the app has a dedicated module to predict the expected ground-shaking intensity and the available lead time at the user's position and to provide customized messages to inform the user about the proper reaction to adopt during the alert. We first present the architecture of both the network-based system and EWApp and then describe its essential operational modes. The app is designed in a way that is easily exportable to any other network-based early warning system.

Post-Earthquake Reparability of Buildings: The Role of Non-Structural Elements

Recent earthquake events in New Zealand have highlighted the need to improve the post-earthquake reparability of buildings. This paper describes a number of avenues for improving the post-earthquake reparability of buildings and reviews a number of recent and ongoing efforts to improve post-earthquake reparability in New Zealand. Attention is given to the role that non-structural elements play in the reparability of buildings. The work explains how the design and detailing of non-structural elements can be enhanced to achieve improved reparability. To reduce the vulnerability of drift-sensitive non-structural elements, such as plasterboard partition walls, a number of alternative detailing strategies are under development. For acceleration-sensitive components such as ceilings and suspended piping, issues with the industry design, installation and inspection provisions are highlighted and ongoing research aimed at understanding system interaction effects is discussed. The last part of the paper proposes different ways of improving reparability during the conceptual design of a building. Various possibilities are identified, such as the definition of inspection and repair criteria and the relocation of non-structural elements away from structural locations to improve access to non-structural elements. It is concluded that by considering potential inspection and repair needs during concept design, considerable time and repair cost could be saved following intense earthquake shaking, with considerable socio-economic benefits for the community.

Influence of random heterogeneity of shear wave velocity on sliding mass response and seismic deformations of earth slopes

Soil shear wave velocity has been recognized as a governing parameter in the assessment of the seismic response of slopes. The spatial variability of soil shear wave velocity can influence the seismic response of sliding mass and seismic displacements. However, most analyses of sliding mass response have been carried out by deterministic models. This paper stochastically investigates the effect of random heterogeneity of shear wave velocity of soil on the dynamic response of sliding mass using the correlation matrix decomposition method and Monte Carlo simulation (MCS). The software FLAC 7.0 along with a Matlab code has been utilized for this purpose. The influence of statistical parameters on the seismic response of sliding mass and seismic displacements in earth slopes with different inclinations and stiffnesses subject to various earthquake shakings was investigated. The results indicated that, in general, the random heterogeneity of soil shear modulus can have a notable impact on the sliding mass response and that neglecting this phenomenon could lead to underestimation of sliding deformations.

Structural health monitoring and seismic response assessment of bridge structures using target-tracking digital image correlation

Our nation’s infrastructure is aging and deteriorating which increases the need for condition assessment and structural health monitoring. For this purpose, there is a growing interest in using non-contact monitoring methods because of the challenges associated with deploying and installing conventional instrumentation. Target-tracking digital image correlation (DIC) is among these methods and is the focus of this paper. Several research activities have been conducted at the University of Nevada, Reno in the field of dynamic monitoring using DIC and presented here. The first part of the paper is concerned with a large-scale laboratory application where target-tracking DIC was utilized to monitor the response of a bridge structure tested under bidirectional earthquake shaking. The 3D dynamic response of the bridge, along with modal properties, i.e. natural frequency, damping ratio, and mode shapes, were measured or determined using both DIC and conventional instrumentation then compared for validation purposes. The second part of the paper presents results from field monitoring of an actual footbridge under pedestrian loading to determine the vibration frequencies of the bridge, and again compare it against results from conventional accelerometers for validation. From both applications, the DIC is demonstrated to successfully capture (1) peak and residual bridge deck rotation and deformation under different earthquake intensity levels and (2) modal properties for system identification. Practical DIC sampling rates were used to accurately monitor and capture the dynamic response of bridges, which shows a high potential for using DIC for larger structural health monitoring applications and future reconnaissance works.

Cause and level of treatment of injuries from earthquake damage to commercial buildings in New Zealand

This study assesses the number of injuries directly caused by structural and non-structural damage within New Zealand commercial buildings from notable shaking events between 2010 and 2014 and the treatment level required. After applying filtering to a comprehensive New Zealand earthquake-induced injury database, 947 injuries matched this study’s scope, of which 174 were fatal. Collapse or movement of non-structural elements caused 556 injuries; though over 85% were treated outside hospitals and none were fatal. In contrast, 60% of the 220 structural damage-related injuries were fatal. The high injury occurrence from non-structural damage highlights its high risk of injury burden. The two leading causes of non-structural damage-related injuries were movement and/or damage of contents (e.g. furniture) and ceiling and services damage. This emphasizes the importance of reducing injury from movement and damage of non-structural elements during earthquake shaking, in addition to reducing fatalities by preventing structural and masonry collapse.

Postdisaster image‐based damage detection and repair cost estimation of reinforced concrete buildings using dual convolutional neural networks

AbstractReinforced concrete (RC) buildings are commonly used around the world. With recent earthquakes worldwide, rapid structural damage inspection and repair cost evaluation are crucial for building owners and policy makers to make informed risk management decisions. To improve the efficiency of such inspection, advanced computer vision techniques based on convolutional neural networks have been adopted in recent research to rapidly quantify the damage state (DS) of structures. In this article, an advanced object detection neural network, named YOLOv2, is implemented, which achieves 98.2% and 84.5% average precision in training and testing, respectively. The proposed YOLOv2 is used in combination with the classification neural network, which improves the identification accuracy for critical DS of RC structures by 7.5%. The improved classification procedures allow engineers to rapidly and more accurately quantify the DSs of the structure, and also localize the critical damage features. The identified DS can then be integrated with the state‐of‐the‐art performance evaluation framework to quantify the financial losses of critical RC buildings. The results can be used by the building owners and decision makers to make informed risk management decisions immediately after the strong earthquake shaking. Hence, resources can be allocated rapidly to improve the resiliency of the community.

Comparative response of Kashmir Basin and its surroundings to the earthquake shaking based on various site effects

The Kashmir Basin is located in seismic zone V, seismogenic faults and damaging earthquakes of 1555, 1885 and 2005 support this classification. Tectonic features are preserved in older hard rocks, and soft-sediment deformation structures (seismites) in the Karewa deposits. Older basement rocks are overlain unconformably by ~1300 m Karewa deposits followed by unconsolidated fluvial sediments that greatly influence earthquake amplitude and duration of shaking. Seismic waves show a drastic change in peak ground velocity and acceleration when travelling through Karewa deposits. The surrounding epicentre zones are dominated by large earthquakes with shallow depth (4–24 km). Ruggedness, steep-slopes and basin curvature can cause PGA amplification during an unpredicted earthquake. The ill consideration of infrastructure on the water saturated rugged terrain causes ground collapse, and consequently threat to life during seismic shaking. The proximity and linear trend of tectonic structures, epicentre distribution, shallow depth seismicity, thickness and material properties of near surface sediments are unfavourable for safety of the infrastructure and the population.

NUMERICAL ANALYSIS OF LIQUEFACTION PHENOMENON BY USING UBC3D-PLM CONSTITUTIVE MODEL

This research is considering of numerical analysis of liquefaction phenomenon by using UBC3D-PLM constitutive model. Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. The UBC3D-PLM is one of the most commonly used constitutive models for liquefaction problems in practice. Even though it is an advanced model, it is relatively simple to apply, since it has a reasonable number of parameters that can be extracted from laboratory or in situ tests. The model was initially developed for sand-like soils having the potential for liquefaction under seismic loading. The UBC3D-PLM model has been developed by Tsegayce (2010) and implemented as a user defined model in PLAXIS. In this research, the capability of this model is considered by using PLAXIS software. The real data of El Centro earthquake 1940, Imperial Valley earthquake 1979 and Upland earthquake 1990 were used. The results of the simulation have shown resembling trend of the UBC3D-PLM and HSSMALL models. This research compare between the results which get after earthquake on liquefied sand and strong layer (coarse sand).

Evaluating Slope Deformation of Earth Dams Due to Earthquake Shaking Using MARS and GMDH Techniques

Assessing the behavior of earth dams under dynamic loads is one of the most significant problems with the design of such large structures. The purpose of this study is to provide new models for predicting dam dispersion in real earthquake conditions. In the first phase, 103 real cases of deformation in earth dams were collected and analyzed due to earthquakes that occurred over recent years. Using nonlinear and machine learning techniques, i.e., group method of data handling (GMDH) and multivariate adaptive regression splines (MARS), two models for prediction of the slope deformation in earth dams under the various types of earthquakes were applied and developed. The main parameters used in these simulation techniques were earthquake magnitude (Mw), fundamental period ratio (Td/Tp), yield acceleration ratio (ay/amax) as inputs and value of slope deformation (Dave) as output. Finally, in order to check the accuracy of the results of the new models, a comparison was made with the previous relations and models in seismic conditions for the slope deformation in earth dams. The results showed that the MARS model, which is able to provide a mathematical equation, has a better result than the GMDH model. These new models are recommended to be used for future analyses based on their flexible capabilities.

An integrated SEM-Newmark model for physics-based regional coseismic landslide assessment

Earthquake-induced landslides are one of the most catastrophic effects of earthquakes, as evidenced by many historic events over the past decades, such as the 1994 Northridge earthquake in California and the 2008 Wenchuan earthquake in China. Realistic prediction of coseismic landslides is crucial for the design of key infrastructure and to protect human lives in seismically active regions. To date, analytical methods for estimating coseismic landslides have been based on highly simplified models. In this study, an integrated Spectral Element Method (SEM)-Newmark model is developed to directly simulate three-dimensional wave field in complex topography on a regional scale, while the associated landslide is indicated by the Newmark sliding displacement analysis considering key model factors. Topographic amplification, soil response, near-field characteristics of earthquake shaking and hydrogeological conditions can be simulated, and their effects on coseismic landslides are studied. In this paper, two regional-scale case studies were conducted using the developed SEM-Newmark model, including landslide hazard assessment for natural terrain in the western part of Hong Kong island, and the massive landslides occurred during the 2014 M6.5 Ludian earthquake in China. These case studies demonstrated that the proposed integrated model can be effectively used for regional-scale coseismic landslide hazard assessment under various earthquake scenarios and hydrogeological conditions.

Landslides triggered after the 16 August 2018 Mw 5.1 Molise earthquake (Italy) by a combination of intense rainfalls and seismic shaking

On 16 August 2018, a Mw 5.1 earthquake occurred in the Molise region (Central Italy) during an intense rainfall event which cumulated up to 140 mm in 3 days. Within 5 days after the seismic event, 88 landslides were surveyed and classified in disrupted and coherent as well as in first-time failures and reactivation. As it resulted by the inventorying, most of the surveyed ground effects were represented by coherent landslides involving clays, marly clays, and cover deposits on low dipping slopes. A spatial distribution analysis of landslides in relation to seismic action and rainfall intensity was carried out to evaluate the possible contribution of both the rainfall-induced saturation and the earthquake shaking to landslide triggering. Based on this analysis, in the epicentral area, it is not possible to clearly split the role of seismic and hydraulic destabilising actions, while, at greater distances, the joined contribution of rainfall and earthquake shaking could have promoted slope failures. Comparisons among collected data and existing worldwide catalogues allow to highlight, through the analysis of the spatial distribution of the surveyed landslides, the possible and not negligible effect of soil saturation during the seismic shaking both in epicentral distance vs. magnitude distribution and in number and spatial concentration of triggered ground effects.

Earthquake Shake Detecting by Data Mining from Social Network Platforms

This study used social media posts of the related effect of earthquakes to derive seismic shake scale distributions in regions of Taiwan and compared it with the regional seismic scale reported by the Central Weather Bureau (CWB) of Taiwan. This study conducted a context searching to scrawl the relationship phrase on the social media network platform, PTT bulletin board system (BBS), to detect the earthquake shake scale using the keywords of the context. In this investigation a decision tree model for analyzing the semantic words from the context of the target event to detect the earthquake shake scale was devised. The results indicate that we can pick out the keywords to use to detect the earthquake shake scale at about 85%. Furthermore, the results of the derived shake scale show that the four studied cases are in a good agreement with the presented news from the CWB of Taiwan. In this study, the author attempted to develop a quick earthquake shake scale detection model by semantic analysis of the collected earthquake disaster information reported on the social media network platform.

Application of monitoring guidelines to induced seismicity in Italy

Public concern about anthropogenic seismicity in Italy first arose in the aftermath of the deadly M ≈ 6 earthquakes that hit the Emilia-Romagna region (northern Italy) in May 2012. As these events occurred in a (tectonically active) region of oil and gas production and storage, the question was raised, whether stress perturbations due to underground industrial activities could have induced or triggered the shocks. Following expert recommendations, in 2014, the Italian Oil & Gas Safety Authority (DGS-UNMIG, Ministry of Economic Development) published guidelines (ILG - Indirizzi e linee guida per il monitoraggio della sismicità, delle deformazioni del suolo e delle pressioni di poro nell’ambito delle attività antropiche), describing regulations regarding hydrocarbon extraction, waste-water injection and gas storage that could also be adapted to other technologies, such as dams, geothermal systems, CO2 storage, and mining. The ILG describe the framework for the different actors involved in monitoring activities, their relationship and responsibilities, the procedure to be followed in case of variations of monitored parameters, the need for in-depth scientific analyses, the definition of different alert levels, their meaning and the parameters to be used to activate such alerts. Four alert levels are defined, the transition among which follows a decision to be taken jointly by relevant authorities and industrial operator on the basis of evaluation of several monitored parameters (micro-seismicity, ground deformation, pore pressure) carried on by a scientific-technical agency. Only in the case of liquid reinjection, the alert levels are automatically activated on the basis of exceedance of thresholds for earthquake magnitude and ground shaking – in what is generally known as a Traffic Light System (TLS). Istituto Nazionale di Geofisica e Vulcanologia has been charged by the Italian oil and gas safety authority (DGS-UNMIG) to apply the ILG in three test cases (two oil extraction and one gas storage plants). The ILG indeed represent a very important and positive innovation, as they constitute official guidelines to coherently regulate monitoring activity on a national scale. While pilot studies are still mostly under way, we may point out merits of the whole framework, and a few possible critical issues, requiring special care in the implementation. Attention areas of adjacent reservoirs, possibly licenced to different operators, may overlap, hence making the point for joint monitoring, also in view of the possible interaction between stress changes related to the different reservoirs. The prescribed initial blank-level monitoring stage, aimed at assessing background seismicity, may lose significance in case of nearby active production. Magnitude – a critical parameter used to define a possible step-up in activation levels – has inherent uncertainty and can be evaluated using different scales. A final comment considers the fact that relevance of TLS, most frequently used in hydraulic fracturing operations, may not be high in case of triggered tectonic events.

Estimating joint stiffness and friction parameters for dry stone masonry constructions

Dry stack stone masonry constructions, such as corbelled vaults, pillared halls composed of monolithic components, and structural walls generally undergo rigid body failure mechanisms such as overturning or sliding under lateral action caused by support settlements or earthquake shaking. Such structural systems rely purely on self-weight and sliding resistance through friction to resist lateral actions. To develop any reliable numerical model for the damage assessment of these stone masonry structures, knowledge of joint normal and shear stiffness along with friction parameters is essential. The objective of the present work is to estimate these joint parameters for dry masonry joints through experimental tests. Joint shear test and axial compression test have been performed on granite stone blocks. Role of various aspects such as surface roughness, pre-compression levels, moisture condition (dry and wet) and dilatancy on the joint behaviour are considered in the 54 joint shear tests conducted. Numerical simulation of the joint behaviour using a model based on discrete element method (DEM) with parameters obtained from the experiments demonstrates a direct application of the outcome of the experiments.

Seismic stability analysis of tunnel face in purely cohesive soil by a pseudo-dynamic approach

To give a solution for seismic stability of tunnel faces subjected to earthquake ground shakings, the pseudo-dynamic approach is originally introduced to analyze tunnel face stability in this study. In the light of the upper-bound theorem of limit analysis, an advanced three-dimensional mechanism combined with pseudo-dynamic approach is proposed. Based on this mechanism, the required support pressure on tunnel face can be obtained by equaling external work rates to the internal energy dissipation and implementing an optimization searching procedure related to time. Both time and space feature of seismic waves are properly accounted for in the proposed mechanism. For this reason, the proposed mechanism can better represent the actual influence of seismic motion and has a remarkable advantage in evaluating the effects of vertical seismic acceleration, soil amplification factor, seismic wave period and initial phase difference on tunnel face stability. Furthermore, the pseudo-dynamic approach is compared with the pseudo-static approach. The difference between them is illustrated from a new but understandable perspective. The comparison demonstrates that the pseudo-static approach is a conservative method but still could provide precise enough results as the pseudo-dynamic approach if the value of seismic wavelengths is large or the height of soil structures is small.

Effect of Earthquakes over Time on the Geogrid-Pile Foundation System in Loose Sand

Researchers and engineers have developed several means to enhance the dynamic lateral stability of civil engineering structures, such as geosynthetic reinforced earth retaining structures to resist excessive earthquake shaking. There is, however, as yet little information about using geogrids with pile foundations under earthquake loadings. This study thus linked a single embedded pile in loose sandy soil with a geogrid, with the system then subjected to two different seismic waves.The laboratory tests were carried out on single pile with a length to diameter ratio of 25 in poorly graded soil (SP) with a relative density of 30%. The geogrid used in the research was Nelton CE121 geogrid (700×700 mm), which was connected with the pile at a depth of 1/8 of the pile length. The model was then subjected to replications of both the Ali Al Gharbi and Halabjah earthquakes, which hit Iraq in 2014 and 2017, respectively.It was found that using geogrid with pile foundation reduced the settlement in the pile by about 50% and 90% for the Halabjah and Ali Al Gharbi earthquake forces, respectively. The maximum bending moment was also reduced, with the bending moment ratio at the pile surface for the Halabjah and Ali Al Gharbi earthquakes being 70% and 50% respectively. The settlement ratio increases as magnitude of earthquake decreases.

Effect of soil structure disturbance on the shear strength of black volcanic ash soil

The effect of soil disturbance on the shear strength of black volcanic ash soil was investigated using a constant volume direct shear apparatus. Disturbance of soil structure was considered as the pore size distribution which obtained from the soil-water characteristic curve (SWCC). The disturbed sample was used as a representation of soil structure disturbance due to earthquake shakes. A series of cyclic tests were conducted under unsaturated and saturated samples. It was found that the undisturbed samples exhibit a unimodal pore structure, and the disturbed samples indicate to a bimodal pore structure. Since the pore structure of the disturbed sample is unstable, the degradation index value is higher than that of the undisturbed sample and increases with the increasing number of cycles. In other words, the cyclic normalized vertical stress of disturbed samples degrades faster. Furthermore, the degradation index value in the normallyconsolidated samples was found to be larger than the overconsolidated. It might be attributed to increasing of the pore water pressure during shearing. Where in the over-consolidated samples is lower than normally-consolidated. On the other hand, the normalized shear stress of unsaturated samples, it is slightly larger due to the suction forces in the total strength of soils.