Induced Seismicity Research Articles

Modeling of Recent Seismicity, Seismic Hazard and Seismotectonic Setting at the New Administrative Capital City Area, Egypt

The new administrative capital city area in Egypt, planned to be constructed in the area between Cairo and Suez cities, is vulnerable to moderate and strong earthquakes, which are inevitable in the region. The moderate size recent earthquake with local magnitude 4.2 took place in the vicinity of administrative capital area on 31st of December 2018. The focal mechanism and ground motion characterization of this event using full waveform inversion and first P-wave polarity techniques are fundamentally studied. This earthquake was simulated at the new administrative capital city area to study the effect of magnitude and source to site distance on the ground motion. Moreover, the seismotectonic setting of the new administrative capital city area is well studied using other earthquakes that have occurred in and around it. Reduction of damage in the administrative capital city area from earthquake ground shaking requires modern building codes that are continuously updated to reflect the effects of ground motions on constructions. This research provides u-p‑to-date, essential and basic seismological results for use in the development and implementation of modern building codes and regulations in Egypt. The most important product, for immediate application by practitioners and policy makers in the region, is the newly developed local seismic hazard charts, which displays the ground acceleration values at different spectral periods. These charts provide the basic seismic input parameter that is considered in all modern building codes containing a-seismic design provisions. Also, artificial earthquake accelerograms were generated for use by the earthquake engineer in the nonlinear dynamic analysis of new or existing structures.

Risk from Oklahoma’s Induced Earthquakes: The Cost of Declustering

ABSTRACTThe U.S. Geological Survey (USGS) has for each year 2016–2018 released a one-year seismic hazard map for the central and eastern United States (CEUS) to address the problem of induced and triggered seismicity (ITS) in the region. ITS in areas with historically low rates of earthquakes provides both challenges and opportunities to learn about crustal conditions, but few scientific studies have considered the financial risk implications of damage caused by ITS. We directly address this issue by modeling earthquake risk in the CEUS using the 1 yr hazard model from the USGS and the RiskLink software package developed by Risk Management Solutions, Inc. We explore the sensitivity of risk to declustering and b-value, and consider whether declustering methods developed for tectonic earthquakes are suitable for ITS. In particular, the Gardner and Knopoff (1974) declustering algorithm has been used in every USGS hazard forecast, including the recent 1 yr forecasts, but leads to the counterintuitive result that earthquake risk in Oklahoma is at its highest level in 2018, even though there were one-fifth as many earthquakes as occurred in 2016. Our analysis shows that this is a result of (1) the peculiar characteristics of the declustering algorithm with space-varying and time-varying seismicity rates, (2) the fact that the frequency–magnitude distribution of earthquakes in Oklahoma is not well described by a single b-value, and (3) at later times, seismicity is more spatially diffuse and seismicity rate increases are closer to more populated areas. ITS in Oklahoma may include a combination of swarm-like events with tectonic-style events, which have different frequency–magnitude and aftershock distributions. New algorithms for hazard estimation need to be developed to account for these unique characteristics of ITS.

Selection of Ground Motions for the Assessment of Liquefaction Potential for South Korea

Recently, some of the most destructive earthquakes have occurred in South Korea since earthquake observations began in 1978. In particular, the soil liquefactions have been reported in Pohang as a result of the ML 5.4 earthquake that occurred in November 2017. Liquefaction-induced ground deformations can cause significant damage to a wide range of buildings and infrastructures. Therefore, it is necessary to take practical steps to ensure safety during an earthquake. In the current seismic design in South Korea, the Hachinohe earthquake and Ofunato earthquake recorded in Japan, along with artificial earthquakes, have been generally used for input motions in dynamic analyses. However, such strong ground motions are only from Japan, and artificial earthquake ground motions are different from real ground motions. In this study, seven ground motions are selected, including those recorded in South Korea, while others are compatible to the current design spectra of South Korea. The effects of the newly selected ground motions on site response analyses and liquefaction analyses are evaluated.

In-Cabinet Response Spectrum Generation Using Frequency Domain Analysis Method

Seismic qualification of instruments and devices mounted on electrical cabinets in a nuclear power plant is performed in this study by means of the in-cabinet response spectrum (ICRS). A simple method and two rigorous methods are proposed in the EPRI NP-7146-SL guidelines for generating the ICRS. The simple method of EPRI can give unrealistic spectra that are excessively conservative in many cases. In the past, the time domain analysis (TDA) methods have been mostly used to analyze a structure. However, the TDA requires the generation of an artificial earthquake input motion compatible to the target response spectrum. The process of generating an artificial earthquake may involve a great deal of uncertainty. In addition, many time history analyses should be performed to increase the accuracy of the results. This study developed a numerical analysis program for generating the ICRS by frequency domain analysis (FDA) method. The developed program was validated by the numerical study. The ICRS calculated by FDA thoroughly matched with those obtained from TDA. This study then confirms that the method it proposes can simply and efficiently generate the ICRS compared to the time domain method.

INFLUENCE OF MATERIAL DAMPING ON THE RESPONSE OF UNDERGROUND STRUCTURES SUBJECTED TO EARTHQUAKE

The paper describes a finite element simulation of the response of a real underground structure subjected to earthquake using GEO5 FEM program. It concentrates on the influence of material damping with respect to a specific type of boundary condition prescribed at the bottom of the analyzed domain. It is seen that considering material damping is inevitable particularly in case of so called fixed boundary conditions to arrive at meaningful results. This is demonstrated on an artificial earthquake generated according to a design spectrum defined in Eurocode 8. A viscous damping ratio combined with the results of eigenvalue analysis is used to derive parameters of Rayleigh damping for three specific scenarios promoting the approach based on the lowest natural frequency as sufficiently accurate for the present task.

Influence of Earthquake Frequency Nonstationarity on Seismic Structural Response

Earthquake ground acceleration records exhibit nonstationarity in both amplitude and frequency content. In order to simplify the random vibration analysis, most earthquake models have often neglected the temporal variation of the frequency content. This is partly because it is difficult to incorporate this variation in ground motion models and also partly because it was believed that it had no substantial effect on structure response. The aim of this paper is to identify the temporal variation in frequency content effects, characterizing the earthquake strong ground motions, on structures. Two comparative stochastic earthquake ground motion models based on the concept of physical spectrum are used to characterize and simulate from a selected ground acceleration record two sets of artificial earthquakes exhibiting similar phases distribution and different frequency contents: the first set presents a time-variant frequency content, and the second has a time-invariant frequency content. Three hysteretic models have been considered, elasto-plastic model (bilinear), Clough’s stiffness degrading model and maximum point-oriented bilinear model. Comparative results are presented to quantify the effects of the time-variant frequency content of earthquake ground motion on the structural response of elastic and inelastic simple systems. It is found that the characteristics of elastic and inelastic structural response depend strongly on the time variation of the frequency content in the seismic input.

Simulating the shake table response of unreinforced masonry cavity wall structures tested to collapse or near-collapse conditions

The seismic performance of existing unreinforced masonry (URM) buildings is considerably affected by typology and level of effectiveness of both construction details and structural components, especially if not originally designed for resisting earthquakes. Within this framework, the use of advanced numerical approaches that are capable of duly accounting for such aspects might improve significantly the assessment of the global response of URM structures. In this article, the applied element method is thus employed for simulating the shake table response of a number of full-scale building specimens representative of cavity wall terraced house construction, used in a number of countries exposed to tectonic or induced seismicity, accounting explicitly for the influence of the presence of both rigid and flexible diaphragms, degree of connections among structural members, and interaction between in- and out-of-plane mechanisms. Although the models slightly underestimated the energy dissipation in some specific cycles prior to collapse, the predicted crack patterns, failure modes, and hysteretic behaviors have shown a good agreement with their experimental counterparts.

Monitoring of a Historical Masonry Structure in Case of Induced Seismicity

ABSTRACT In case of induced seismicity, expectations from a structural monitoring system are different than in the case of natural seismicity. In this paper, monitoring results of a historical building in Groningen (Netherlands) in case of induced seismicity has been presented. Results of the monitoring, particularities of the monitoring in case of induced earthquakes, as well as the usefulness and need of various monitoring systems for similar cases are discussed. Weak soil properties dominate the structural response in the region; thus, the ground water monitoring as well as the interaction of soil movements with the structural response has also been scrutinized. The proposed study could be effectively used to monitor historical structures subjected to induced seismicity and provide useful information to asset owners to classify the structural health condition of structures in their care. It was shown that the in-plane cracks at the building would normally not be expected in this structure during small induced earthquakes happening in Groningen. One explanation provided here is that the soil parameters, such as shrinking of water-sensitive soil layers, in combination with small earthquakes, may cause settlements. The soil effects may superimpose with the earthquake effects eventually causing small cracks and damage.

Seismic Performance Evaluation of Building-Damper System under Near-Fault Earthquake

The building-damper system designed by a seismic code is usually considered to be able to withstand the attack of strong earthquakes. However, near-fault earthquakes, especially those with the forward-directivity effect, might cause early and unexpected failure of code-designed dampers and consequent severe structural damage. In this paper, by taking into account near-fault earthquakes, seismic performance of the building-damper system and damper failure’s influence are evaluated systematically. A 9-storey steel building is designed by the Chinese seismic code as the benchmark model, and five typical dampers, including buckling-restrained brace damper (BRB), friction damper (FD), self-centering damper (SCD), viscous damper (VD), and viscoelastic damper (VED), are adopted. It was found that the building-damper systems show a large response and possible damper failure under the near-fault earthquake excitations. Then, the influence of damper failure is investigated, which reveals that damper failure would significantly affect seismic performance of the building-damper system, especially for the building-SCD system. Subsequently, by introducing the artificial near-fault earthquake excitation, the influences of different pulse parameters, such as pulse velocity amplitude, pulse period, and the number of significant pulses, are studied. It shows that the pulse velocity amplitude and pulse period obviously affect the seismic performance, while the number of significant pulses presents little influence.

Seismic response prediction method for building structures using convolutional neural network

In this study, a method of predicting the seismic responses of building structures based on a convolutional neural network (CNN) is proposed. In the method, the time histories of acceleration responses previously measured in a building during earthquakes are used in the CNN input layer, with the corresponding time histories of the displacement responses being used in the CNN output layer. The correlations between the features automatically extracted from the acceleration responses by the convolution and pooling operations in the various CNN layers and the displacement responses in the CNN output layer are established through CNN training. The trained CNN predicts the displacement responses for a future earthquake event using only the measured acceleration responses. To verify the validity of the proposed method, a numerical study on the ASCE benchmark model and an experimental study on a reinforced concrete frame structure are conducted. In the numerical study, the structural responses of the ASCE model subject to artificial earthquakes are utilized for CNN training, and the performance of the trained CNN is verified through seismic response prediction. In the experimental study, shaking table tests are performed for various earthquakes to measure the seismic responses of the reinforced concrete test structure. The seismic response prediction performance of the proposed method is examined using CNN trained with the measured seismic responses. Furthermore, the performances of CNNs trained with different numbers of datasets generated by the proposed data generation method based on data overlapping with the same data pool are discussed with related to the number of CNN training iteration number.

Support Vector Machine Classification of Seismic Events in the Tianshan Orogenic Belt

AbstractDiscriminating between various types of seismic events is of significant scientific and societal importance. We use a machine learning method employing support vector machine (SVM) to classify tectonic earthquakes (TEs), quarry blasts (QBs), and induced earthquakes (IEs) among 30,181 1.5 <ML<2.9 seismic events that occurred in the Tianshan orogenic belt in China from 2009 to 2017. SVM classifiers are derived based on discriminant features of a training data set consisting of 1,400 TEs selected from the aftershock sequences of 18ML≥ 5.0 earthquakes, 2,881 QBs from repeating events occurring in those areas with a percentage of event daytime occurrence greater than 0.9, and 987 IEs from events in the known oil/gas fields and water reservoirs. The discriminant features include spectral amplitudes of observed P and S wave signals in a frequency range of 1–15 Hz normalized by the P spectrum and averaged over the entire seismic network, and an optional feature of the percentage of event daytime occurrence. Statistics analyses indicate that the accuracies of the SVM classifiers are 99.81% for TEs, 99.93% for QBs, and 99.62% for IEs. Our classification indicates that 37.57% of the seismic events are QBs occurring in possible mine areas and appearing mostly as clusters with a percentage of event daytime occurrence greater than 0.9, 50.12% are TEs occurring in various thrust faults in the Tianshan orogenic belt, and 12.31% are IEs or shallow tectonic earthquakes occurring mostly as clusters near oil and gas fields and water reservoirs. We reevaluatebvalues in the region and obtain relatively uniform values for the classified TEs with most of them below 1.0, as opposed to a large range of values (0.5–2.7) when all the seismic events are used in the analysis.

Induced earthquakes can cause as much damage as tectonic quakes

Induced earthquakes can cause as much damage as tectonic quakes

Ground-Motion Analysis of Hydraulic-Fracturing Induced Seismicity at Close Epicentral Distance

ABSTRACT The application of seismic hazard analysis methods developed for natural earthquakes can provide an effective framework for managing risks of induced seismicity (IS) sequences, particularly for assessment of potential risk to nearby infrastructure. Among various factors, the reliability of these methods depends on the accuracy of the ground-motion prediction equation (GMPE)—especially at close epicentral distances where ground motions are expected to be highest. In addition, potential impacts on local infrastructure can be assessed based on ground-motion-derived intensity values, which provide a basis for some traffic-light protocols that are used for managing fluid IS. GMPEs in many areas of the world, however, are poorly calibrated at close epicentral distances, because the availability of near-source seismograph stations is generally very sparse. This study investigates ground motions generated by an IS sequence, up to local magnitude (ML) 3.77 that occurred during a hydraulic-fracturing stimulation in the Duvernay shale play in central Alberta, western Canada. The sequence was monitored using a near-surface array that was located directly above the hydraulically fractured horizontal wells, providing accurate ground-motion measurements at hypocentral distances <10 km. The local array consisted of a combination of geophones cemented in shallow wellbores to depth of ∼27 m, shallow buried broadband seismometers, and a strong-motion accelerometer. This configuration enabled direct measurement of near-surface seismic velocities in the top 27 m, which provided robust VS30 data used to correct observed ground motions for local site-amplification effects. Our data set extends previous analyses in this region by providing new measurements very close to the epicenters of moderate earthquakes and shows that a recently developed GMPE provides accurate near-source ground-motion estimates.

Neural network-based seismic response prediction model for building structures using artificial earthquakes

In this paper, a new model for predicting seismic responses of buildings based on the correlation of ground motion (GM) and the structure is presented by simulating numerous artificial earthquakes (AEQs). In the model, neural network (NN) configurations representing the relationships between GM characteristics and seismic responses of a structure are developed to predict responses of the structure with only GM data measured by monitoring system in future seismic events. To extract the GM characteristics, multiple AEQs corresponding to the design response spectrum are generated based on probabilistic vibration theory, instead of using historical earthquakes. In the presented NN configurations, GM characteristics including mean and predominant period, significant duration, and peak ground acceleration are established as the input layer and the maximum inter-story drift ratio and maximum displacement are established as the output layer. In addition, a new parameter called resonance area is proposed to represent the relationship between a GM and a target structure in the frequency domain and utilized in the NN input layer. By employing the new parameter, dynamic characteristics of the structure are considered in the response estimation of the model with related to GM. The model is applied to seismic response prediction for four multi-degrees-of-freedom (MDOF) structures with different natural periods using 2700 AEQs. The validities of the presented NN models are confirmed by investigating the performance of response prediction. The effectiveness of the resonance area parameter in the NN for predicting the seismic responses is assessed and discussed. Furthermore, the effects of the constitution of NNs and computational costs of those NNs on estimation were investigated. Finally, the presented model is employed for prediction of seismic responses for a structural model of a planar reinforced concrete building structure.

When Voting Becomes Protest: Mapping Determinants of Collective Action Onto Voting Behavior

Do people signal protest by bringing out a protest vote when they feel they have been collectively disadvantaged? Political scientists have been interested in “protest voting” yet theoretical understanding is limited. Social psychologists have studied other forms of collective protest extensively. The present study integrates insights from the political science approach to protest voting and the social psychological approach to protest behavior to study how a context of perceived collective disadvantage influences voting for protest parties. We conducted a field study with a quasi-experimental design. This allowed us to study effects of a plausibly exogenous variable—the presence versus absence of societal disadvantage (the experience of man-made earthquakes)—on both determinants of and on subsequent protest voting. Results reveal that the presence of earthquakes affects levels of protest voting via (national) trust, regional identification, and perceptions of efficacy.

Seismic catalogs for 'Tan et al., Hydraulic Fracturing Induced Seismicity in the Southern Sichuan Basin Due to Fluid Diffusion Inferred from Seismic and Injection Data Analysis'

Seismic catalogs for 'Tan et al., Hydraulic Fracturing Induced Seismicity in the Southern Sichuan Basin Due to Fluid Diffusion Inferred from Seismic and Injection Data Analysis'

Optimal design of rotational friction dampers for improving seismic performance of inelastic structures

Rotational friction dampers (RFDs) have been proposed as one of the passive control devices in order to enhance the seismic performance of inelastic structures and dissipate the input energy of earthquakes through friction in their rotating plates. The efficiency, performance and design of an RFD strongly depend on its frictional moment and the length of its vertical rigid beam. Hence, the main contribution of this study is to propose an optimal design of the RFD for the seismic vibration control of an inelastic single–story steel moment–resisting frame (SMRF). For achieving this purpose, the parameters of the RFD subjected to an artificial earthquake were first optimized through minimizing the ratio of seismic input energy to dissipated the energy in the RFD. Modeling results show that the optimized RFD is able to give an average reduction of 54%, 75% and 97% versus the structure without an RFD in terms of the maximum and residual roof displacements and the cumulative hysteresis energy of the SMRF, respectively. Then, the seismic performance of the SMRF equipped with the optimized RFD was assessed subjected to four historic earthquake records. The results indicate that the optimal RFD–equipped structure subjected to the historic earthquakes exhibits a better seismic performance in all measures compared with the uncontrolled structure.

The theory development and application of deep nonlinear dynamic rock mechanics

This paper systematically summarized the development of deep nonlinear rock dynamics under the action of strong dynamic loading like explosions. It also pointed out that the structural characteristics of rock mass should be considered when studying the dynamic events such as artificial earthquakes and rockburst. By analyzing the basic deformation characteristics of rock blocks under large-scale explosions, a progressive evolution model to analyze irreversible displacements of rock mass was constructed. The relationship between the sizes of activated rock blocks under explosions with different equivalent and their distance from the explosion centers was established. A calculation method to determine the safe distance of earthquakes induced by underground nuclear explosions was proposed according to the range of irreversible displacement. The validity of the theoretical methods was comprehensively verified by comparing with underground nuclear test data of the United States, Russia and France.

Flood 2018 and the status of reservoir-induced seismicity in Kerala, India

Floods in India, which were once mostly confined to southern part of the Himalayan region, have now started spreading over to many regions of India, including the urban conglomerations and the desert tracts of Rajasthan too. The flood that occurred in Kerala during August 2018 is one such major disaster that caused huge damages to man, infrastructure and properties, estimated to the worth of 200 billion USD. Besides, they are expected to cause a chain of other hazards, and one among these is reservoir-induced seismicity (RIS). The RIS occurs in deep reservoirs with high water column. While the water column increases the total stress on the earth crust, the infiltration causes pore pressure increase which in turn decreases the effective strength of the earth crust. Such changes in the stress regime cause RIS (earthquake). The rocks of the Western Ghat Mountains of Kerala are highly deformed with folds and faults of Archean/Precambrian tectonics and have undergone morphological modifications during Pleistocene tectonics. The region is also seismically active. Further, the Western Ghats cover vast area in Kerala; almost all the dams and reservoirs are located in the highly folded, fractured, faulted and along the deep valleys of the Western Ghats. In the context of recent August 2018 flood disaster, the probability of RIS has increased. So, GIS analysis was carried out using various geosystems, seismicity, distribution of dams, zones of heavy rainfall 2018 and the flood inundation, which indicates that 50% of the reservoirs are highly prone to RIS. The RIS would have occurred during August 2018 flood itself, but for the release of water from the overflowing reservoirs. However, owing to the proneness of the region to RIS, optimal water management is necessary for the dams and reservoirs of Kerala.

Using Infrared Spectroscopy to Study the Mineral Composition of Shear Fracture Surfaces in Rocks

Infrared-reflection and transmission spectroscopy was used to study the mineral composition of a shear fracture surface in a core recovered from a well in the seismically active Koyna-Varna region in western India, which is associated with reservoir-induced seismicity. Methods for conducting comprehensive experimental studies of the mineral composition of shear fracture surfaces in rocks are described. The experiments demonstrated the wide possibilities of these techniques and allowed us to obtain new results on shear fractures, which are important for further research on the physics of earthquake foci. It is established that the shear fracture surface is a three-layer structure. The upper layer contains only glauconite nanocrystals. The layer beneath it contains, in addition to glauconite, calcite and montmorillonite crystals. The total thickness of these layers is about 600 µm. Below these layers is the host rock, which contains calcite, dolomite, and glauconite. The number of illite–smectite layers in glauconite nanocrystals has been determined. The upper layer contains nanocrystals consisting of ∼30 layers. In the second layer, the crystals of this mineral contain ∼25 layers. Finally, in the host rock, glauconite crystals make up ∼20 layers.