Simulation Of Earthquake Ground Motions Research Articles

Ground motion simulations of great earthquakes on the Alpine Fault: effect of hypocentre location and comparison with empirical modelling

ABSTRACTThis paper discusses simulated ground motion intensity, and its underlying modelling assumptions, for great earthquakes on the Alpine Fault. The simulations utilise the latest understanding of wave propagation physics, kinematic earthquake rupture descriptions and the three-dimensional nature of the Earth's crust in the South Island of New Zealand. The effect of hypocentre location is explicitly examined, which is found to lead to significant differences in ground motion intensities (quantified in the form of peak ground velocity, PGV) over the northern half and southwest of the South Island. Comparison with previously adopted empirical ground motion models also illustrates that the simulations, which explicitly model rupture directivity and basin-generated surface waves, lead to notably larger PGV amplitudes than the empirical predictions in the northern half of the South Island and Canterbury. The simulations performed in this paper have been adopted, as one possible ground motion prediction, in the ‘Project AF8’ Civil Defence Emergency Management exercise scenario. The similarity of the modelled ground motion features with those observed in recent worldwide earthquakes as well as similar simulations in other regions, and the notably higher simulated amplitudes than those from empirical predictions, may warrant a re-examination of regional impact assessments for major Alpine Fault earthquakes.

Toward Exascale Earthquake Ground Motion Simulations for Near-Fault Engineering Analysis

Modernizing SW4 for massively parallel time-domain simulations of earthquake ground motions in 3D earth models increases resolution and provides ground motion estimates for critical infrastructure risk evaluations. Simulations of ground motions from large (M ≥ 7.0) earthquakes require domains on the order of 100 to500 km and spatial granularity on the order of 1 to5 m resulting in hundreds of billions of grid points. Surface-focused structured mesh refinement (SMR) allows for more constant grid point per wavelength scaling in typical Earth models, where wavespeeds increase with depth. In fact, MR allows for simulations to double the frequency content relative to a fixed grid calculation on a given resource. The authors report improvements to the SW4 algorithm developed while porting the code to the Cori Phase 2 (Intel Xeon Phi) systems at the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Investigations of the performance of the innermost loop of the calculations found that reorganizing the order of operations can improve performance for massive problems.

Simulation of Earthquake Ground Motions in the Eastern United States Using Deterministic Physics‐Based and Site‐Based Stochastic Approaches

Abstract Earthquake ground‐motion recordings are scarce in the central and eastern United States (CEUS) for large‐magnitude events and at close distances. We use two different simulation approaches, a deterministic physics‐based method and a site‐based stochastic method, to simulate ground motions over a wide range of magnitudes. Drawing on previous results for the modeling of recordings from the 2011 M w 5.8 Mineral, Virginia, earthquake and using the 2001 M w 7.6 Bhuj, India, earthquake as a tectonic analog for a large magnitude CEUS event, we are able to calibrate the two simulation methods over this magnitude range. Both models show a good fit to the Mineral and Bhuj observations from 0.1 to 10 Hz. Model parameters are then adjusted to obtain simulations for M w 6.5, 7.0, and 7.6 events in the CEUS. Our simulations are compared with the 2014 U.S. Geological Survey weighted combination of existing ground‐motion prediction equations in the CEUS. The physics‐based simulations show comparable response spectral amplitudes and a fairly similar attenuation with distance. The site‐based stochastic simulations suggest a slightly faster attenuation of the response spectral amplitudes with distance for larger magnitude events and, as a result, slightly lower amplitudes at distances greater than 200 km. Both models are plausible alternatives and, given the few available data points in the CEUS, can be used to represent the epistemic uncertainty in modeling of postulated CEUS large‐magnitude events.

Earthquake ground motion simulation at Zoser pyramid using the stochastic method: A step toward the preservation of an ancient Egyptian heritage

Strong ground shaking during earthquakes can greatly affect the ancient monuments and subsequently demolish the human heritage. On October 12th 1992, a moderate earthquake (Ms=5.8) shocked the greater Cairo area causing widespread damages. Unfortunately, the focus of that earthquake is located about 14km to the south of Zoser pyramid. After the earthquake, the Egyptian Supreme council of antiquities issued an alarm that Zoser pyramid is partially collapsed and international and national efforts are exerted to restore this important human heritage that was built about 4000years ago. Engineering and geophysical work is thus needed for the restoration process. The definition of the strong motion parameters is one of the required studies since seismically active zone is recorded in its near vicinity. The present study adopted the stochastic method to determine the peak ground motion (acceleration, velocity and displacement) for the three largest earthquakes recorded in the Egypt’s seismological history. These earthquakes are Shedwan earthquake with magnitude Ms=6.9, Aqaba earthquake with magnitude Mw=7.2 and Cairo (Dahshour earthquake) with magnitude Ms=5.8. The former two major earthquakes took place few hundred kilometers away. It is logic to have the predominant effects from the epicentral location of the Cairo earthquake; however, the authors wanted to test also the long period effects of the large distance earthquakes expected from the other two earthquakes under consideration. In addition, the dynamic site response was studied using the Horizontal to vertical spectral ratio (HVSR) technique. HVSR can provide information about the fundamental frequency successfully; however, the amplification estimation is not accepted. The result represented as either peak ground motion parameters or response spectra indicates that the effects from Cairo earthquake epicenter are the largest for all periods considered in the present study. The level of strong motion as indicated by peak ground acceleration reaches the value of 250gals which is considerably high. At the end, it is worth to mention that the information resulted from the present work may be useful for the planned restoration decision of the Zoser pyramid site.

Assessment of acceleration responses of a railway bridge using wavelet analysis

One of more effective and practical ways in Structural Health Monitoring (SHM) is assessing structural movements and detecting corresponding damages in both time and frequency domains. Recently, the wavelet analysis has been used widely in many engineering applications, e.g., SHM, damage detection, and simulation of earthquake ground motions. In this study, the wavelet analysis in one and two dimensions is applied to investigate and assess the movement behavior of a high-speed train railway bridge using the acceleration measurements. Moreover, the wavelet analysis is used to evaluate the degree of correlation between different acceleration measurement points under the different passage train speeds. The high-speed train railway bridge is a double track steel box girder bridge with 50 m length. The high-speed train was controlled to pass over the bridge with four different speeds, i.e. 290, 360, 400, and 406 km/hr. Furthermore, two train passage cases were considered to examine the main girder's deformation behavior under loaded and unloaded railway tracks simultaneously. The results show that the wavelet analysis proves to be an efficient tool to investigate the frequency content of the acceleration measurements. Finally, the unloaded track suffers more vibration than the loaded track particularly when increasing the train speed.

Kinematic source models for long-period ground motion simulations of megathrust earthquakes: validation against ground motion data for the 2003 Tokachi-oki earthquake

In this study, a method for simulating the ground motion of megathrust earthquakes at periods of approximately 2 s and longer was validated by using the characterized source model combined with multi-scale spatial heterogeneity. Source models for the M W 8.3, 2003 Tokachi-oki earthquake were constructed, and ground motion simulations were conducted to test their performance. First, a characterized source model was generated based on a source model obtained from waveform inversion analysis. Then, multi-scale heterogeneity was added to the spatial distribution of several source parameters to yield a heterogeneous source model. An investigation of the Fourier spectra and 5 % damped velocity response spectra of the simulated and observed ground motions demonstrated that adding multi-scale heterogeneity to the spatial distributions of the slip, rupture velocity, and rake angle of the characterized source model is an effective method for constructing a source model that explains the ground motion at periods of 2–20 s. It was also revealed how the complexity of the parameters affects the resulting ground motion. The complexity of the rupture velocity had the largest influence among the three parameters.

Acceleration response spectra for Tbilisi city with site effects

The utilization of time histories of earthquake ground motion has grown considerably in the field of earthquake engineering. It is very unlikely, however, that recordings of earthquake ground motion will be available for all sites and conditions of interest. Hence, there is a need for efficient methods for the simulation of strong ground motion for a given region. Due to lack of the real strong ground motion records the objective of this research is to develop a methodology for rapid generation of horizontal and vertical components of earthquake ground motion at any site for Tbilisi city. The model developed in this study provides simulation of ground motion over a wide range of magnitudes and distances at 8 earthquake sources zones of Tbilisi region (within 50 km). The research includes three main topics: (i) the stochastic simulation of earthquake ground motion at a given site of the city of Tbilisi; (ii) the estimation of acceleration time histories at a given site using the direct method of engineering seismology considering soil conditions based on the theory of the reflected waves and (iii) calculation of horizontal and vertical acceleration elastic response spectra for main sites of Tbilisi territory. The simulation procedure typically consists of multiplying deterministic modulating function with a stationary process of known power spectral density. The obtained results in the terms of normalized elastic response spectra can be widely applied in the practice of earthquake engineering in Georgia.

Broadband Strong Ground Motion Simulations of Large Subduction Earthquakes

The great subduction earthquakes that occurred recently in Peru, Chile, and Japan have provided unprecedented information about the ground motions generated by such earthquakes. The 23 June 2001 M 8.4 Peru earthquake was recorded at eight strong-motion stations; the 27 February 2010 M 8.8 Maule, Chile, earthquake was recorded at over 10 strong-motion stations; and the 11 March 2011 M 9.0 Tohoku, Japan, earthquake was recorded at more than a thousand stations and produced the most extensive dataset of recordings for any earthquake. For the first time, data are available to guide the generation of ground-motion simulations from great subduction earthquakes. Broadband ground-motion simulations can enhance the usefulness of the recordings of these earthquakes by providing a means of interpolating and extrapolating the recorded data. Once they have been validated, broadband ground-motion simulations can be used for forward predictions of the ground motions of great subduction events in regions such as Cascadia, in which there are no strong-motion recordings of large subduction earthquakes. In this study, we test our ability to use a hybrid method to simulate broadband strong-motion recordings of megathrust earthquakes by demonstrating that our simulations reproduce the amplitudes of the recorded ground motions without systematic bias. We use simulations to study the distribution of various intensity measures of ground motion caused by these earthquakes and to validate our ground-motion simulation method by comparing the simulated ground motions with recorded ground motions as well as with empirical ground-motion prediction models.

A multi-modal analytical non-stationary spectral model for characterization and stochastic simulation of earthquake ground motions

A novel stochastic earthquake ground motion model is formulated in association with physically interpretable parameters that are capable of effectively characterizing the complex evolutionary nature of the phenomenon. A multi-modal, analytical, fully non-stationary spectral version of the Kanai–Tajimi model is introduced achieving a realistic description of the time-varying spectral energy distribution. The functional forms describing the temporal evolution of the model parameters can efficiently model highly non-stationary power spectral characteristics. The analysis space, where the analytical forms describing the evolution of the model parameters are established, is the energy domain instead of the typical use of the time domain. This space is used in conjunction with a newly defined energy-associated amplitude modulating function. The Spectral Representation Method can easily support the simulation of sample model realizations. A subset of the NGA database is selected in order to test the efficiency and versatility of the stochastic model. The complete selected database is thoroughly analyzed and sample observations of the model parameters are obtained by fitting the evolutionary model to its records. The natural variability of the entire set of seismic ground motions is depicted through the model parameters, and their resulting marginal probability distributions together with their estimated covariance structure effectively describe the evolutionary ground motion characteristics of the database and facilitate the characterization of the pertinent seismic risk. For illustration purposes, the developed evolutionary model is presented in detail for two example NGA seismic records together with their respective deterministic model parameter values.

SEISMOLOGICAL INVESTIGATION AT MEKAAD RADWAN OTTOMAN PERIOD- CAIRO-EGYPT (a)

Earthquakes are generally considered the most dangerous factor affecting the historicalbuildings. The present study is focusing on the determination of the effects of earthquakeactivities on the historical site of Mekaad Radwan Compound near outskirt of old FatimidCairo, the area of Bab Zwiela Bawabat El Metwali. The analysis of the seismicity dataaround the site under investigation is carried out to define the design or credible earthquake.In order to achieve the scientific, practical works; seismotectonics, Simulation of earthquakeground motion in the site and site response are studied. The deterministic and probabilisticapproaches were carried out showing that the credible earthquake may be located at thesame seismic zone of Cairo 1992 earthquake.

An Equivalent Point‐Source Model for Stochastic Simulation of Earthquake Ground Motions in California

Response spectra for California earthquakes of 3.0≤ M 0.2 Hz. We finish the paper by providing a recipe for developing a simulation‐based generic ground‐motion prediction equation that can be adjusted for source and attenuation attributes in different regions by simple modifications to its key source and attenuation modeling parameters.

Simulation of broadband seismic ground motions at dam canyons by using a deterministic numerical approach

As a deterministic numerical approach for simulation of earthquake ground motions, the spectral element method (SEM) is applied to generate a broadband acceleration array for dam-canyons instead of the traditional empirical or stochastic methods. Specifically, the SEM analysis model with an extra fine mesh is used for the Pacoima Canyon to simulate the entire path starting from earthquake source rupture via the propagation medium to the local site. The source and the 3D earth model (velocity structure) are validated through the modeling of the Newhall earthquake on 28 October 2012 at a frequency of up to 8Hz. Subsequently, the San Fernando earthquake records on 13 January 2001 are further used to study the effects of propagation path in simulation. Finally, the spatially varying ground motions at the Pacoima Canyon are obtained for different source mechanisms. The results show that the source mechanism and the local site topography significantly affect the distribution of the peak accelerations along the canyon.

Introduction to the Focus Section on Validation of the SCEC Broadband Platform V14.3 Simulation Methods

This Special Focus Section comprises a collection of eight papers describing recent advances in methods for the broadband simulation of earthquake ground motions and their evaluation against recorded data and empirical models. In the jargon of engineering seismology, “broadband” implies seismograms with periods ranging from less than 0.1 s to greater than 10 s. Broadband simulations are of scientific and engineering interest because they provide complete time histories that can be useful in ground‐motion forecasting, especially for parameter ranges that are poorly sampled by observed seismograms. The papers in this collection document a coordinated exercise, conducted by the Southern California Earthquake Center (SCEC) in collaboration with the Pacific Earthquake Engineering Research (PEER) Center, which takes important steps toward validating broadband simulation methods for engineering purposes. The exercise was driven by two major hazard modeling efforts, the South Western United States (SWUS) ground‐motion characterization project and the PEER Next Generation Attenuation project for central and eastern North America (NGA‐East). Both projects require simulations to supplement observations for constraining ground‐motion prediction equations (GMPEs) and characterizing their epistemic uncertainties. The first paper, by Goulet et al. (2015), describes the objectives and design of the study. The validations were done in two parts: against …

Machine-Learning Methods for Earthquake Ground Motion Analysis and Simulation

This paper presents a novel method of data-based probabilistic seismic hazard analysis (PSHA) and ground motion simulation, verified using previously recorded strong-motion data and machine-learning techniques. The procedure consists of three parts: (1) selection of an orthonormal set of basis vectors called eigenquakes to represent characteristic earthquake records; (2) estimation of response spectra for the anticipated level of shaking for a scenario earthquake at a site using Gaussian process regression; and (3) optimal combination of the eigenquakes to generate time series of ground acceleration consistent with the response spectral ordinates obtained in the second part. The paper discusses the benefits of applying such machine-learning methods to strong-motion databases for PSHA and ground motion simulation, particularly in large urban areas where dense instrumentation is available or expected. The effectiveness of the proposed methodology is exhibited using four scenario examples for downtown Los Angeles. Advantages, disadvantages, and future research needs for this machine-learning approach to PSHA are discussed.

Virtual topography: A fictitious domain approach for analyzing free‐surface irregularities in large‐scale earthquake ground motion simulation

SUMMARYThis paper presents a numerical scheme based on a fictitious domain framework for the numerical modeling of earthquake‐induced ground motion in the presence of realistic surface topography of the Earth's crust. We show that by adopting a non‐conforming octree‐based meshing approach associated with a virtual representation of the surficial irregularity, we can obtain accurate representations of ground motion. From the computational point of view, our methodology proves to be also efficient, and more importantly, it allows us to preserve the salient features of multi‐resolution cubic‐shaped finite elements for wave propagation applications. We implemented the non‐conforming meshing scheme for the treatment of realistic topographies into Hercules, the octree‐based finite‐element earthquake simulator developed by the Quake Group at Carnegie Mellon University. We tested the benefits of the strategy by benchmarking its results against reference examples, and by means of numerical error estimate analyses. Our qualitative and quantitative comparisons showed a close agreement between our numerical results and the reference results, and also, that the order of convergence of the displacement field is preserved in the presence of surface topography. Moreover, this performance was obtained by using the same mesh refinement techniques with cubic elements as in traditional flat free‐surface simulations. Copyright © 2014 John Wiley & Sons, Ltd.

New insights in the analysis of the structural response to response-spectrum-compatible accelerograms

This paper addresses the study of the seismic response of structures to response-spectrum-compatible accelerograms. The number of methodologies proposed in the last three decades to simulate artificial earthquake ground motion testifies the relevance of this subject in the scientific community. However, the implications of the selection of models and hypothesis adopted and their impact on the structural response have not been thoroughly highlighted yet. This contribution shows for the first time that different ground motion models, having identical response spectrum at 5% damping, peak ground acceleration, strong motion phase and total duration, can lead to significant discrepancies in the structural responses even for proportionally damped linear behaving structures, although all the models are satisfying the response-spectrum compatibility criteria. The results show clearly the weakness in the current response-spectrum-compatible criteria provided by seismic codes and the necessity of more robust conditions for the simulation of artificial earthquake ground motions.

Testing of small‐scale models of masonry buildings on simple earthquake simulators: possibilities and limits / Tests mit kleinformatigen Modellen von Mauerwerksgebäuden auf einfachen Erdbebensimulatoren: Möglichkeiten und Grenzen

AbstractExperience regarding the testing of models of masonry buildings on simple shaking tables is discussed. It is stressed that because scale effects affect some phenomena and influence the dynamic response, only overall seismic behaviour of structural systems can be studied by testing reduced size models, and not structural details. The basic principles of physical modelling are explained and options for preparing different types of models presented. The test facility, needed for simulation of earthquake ground motion, is described and pointers are given for the selection of simulated earthquakes. Some practical cases of model shaking table studies are also presented.

表層地盤の３次元的影響を考慮した2003年宮城県北部地震の震源域における地震動のシミュレーション

2003 年7 月26 日7 時13 分に発生した2003 年宮城県北部地震 (Mj 6.4) の際に，震源域の石巻市で確認された周期約1秒の顕著な後続位相の発生メカニズムを明らかにするために大規模並列計算機を用いた地震動シミュレーションを行った。まず，震源域周辺において重力異常値の短波長成分と余震観測記録のS波部に着目した波形逆解析により同定された1次元S波速度構造を用いて，深部地盤の3次元地下構造モデルを構築した。さらに既往の研究資料を用いて，石巻平野の沖積層からなる表層地盤の3次元モデルも作成した。構築した地盤モデルでの地震波伝播の定性的な理解のために，2003 年7 月28 日4 時8 分 (Mj 5.1) の余震による地震動の2次元差分法シミュレーションを実施し，平野部では沖積層の盆地構造の影響によって後続位相が現れることを明らかにした。つぎに，この余震の3 次元差分法によるシミュレーションを行った。計算では，東工大スーパーコンピュータTSUBAMEの200個のCPUを用いて，MPIで実装された並列アルゴリズムに基づく方法によって周期0.75秒以上の地震波を再現した。計算結果では，振幅や波形のより定量的な評価が可能となり，地下構造モデルが妥当なものであることを示した。さらに，同様の手法で本震による3次元地震動シミュレーションを行うことによって，顕著な後続位相の存在を再現できた。この後続位相は地表に到達した実体波が堆積層の不規則性によって表面波に変換され，地盤で増幅されながら平野を伝わった波であることが明らかとなった。計算された最大地動速度分布を求めると，震源のアスペリティの影響と地盤の影響により振幅が大きくなる領域と，地盤のみの影響により振幅が大きくなる領域があることがわかった。さらに，計算加速度波形をもとに算出した計測震度分布は震源域での観測値をおおむね説明することができた。

Earthquake Ground-Motion Simulation including Nonlinear Soil Effects under Idealized Conditions with Application to Two Case Studies

Nonlinear soil behavior in sediments remains one of the most relevant and challenging aspects in site characterization. Geotechnical engineers began studying soil changes in the shear modulus and damping ratio with increasing strain amplitude in the late 1960s and early 1970s (e.g., Seed and Idriss, 1969; Hardin and Drnevich, 1972). However, the influence of soil nonlinearities on the ground motion, in places other than those involving liquefaction, was not fully accepted by seismologists until observations made after the 1989 Loma Prieta and 1994 Northridge earthquakes, and from monitoring projects such as the SMART1 and SMART2 arrays in Taiwan (Field et al. , 1998; Aki, 2003). These events and arrays showed that soil nonlinearities caused permanent deformations away from the source, reductions in soil‐to‐rock ratios by average factors of 2 with respect to those of smaller events, and reductions in shear moduli and shear‐wave velocities of up to 80% and 50%, respectively (e.g., Wen, 1994; Beresnev et al. , 1995; Field et al. , 1997). Soil nonlinearities seem to be more prominent in frequency ranges from 0.5 to 4 Hz (e.g., Darragh and Shakal, 1991; Field et al. , 1997; Beresnev, 2002), and have been associated with peak ground acceleration values above 0.1–0.2 g and shear strains larger than 10−5 to 10−4 (e.g., Chang et al. , 1989; Chin and Aki, 1991; Beresnev and Wen, 1996; Trifunac and Todorovska, 1996). Modeling and simulation of nonlinear soil behavior and effects also date back to the 1960s and 1970s (e.g., Idriss and Seed, 1968; Schnabel, Seed, and Lysmer, 1972; Joyner and Chen, 1975). Early 1D and 2D studies were mostly done using equivalent linear models. Although these models do not capture all the characteristics …

An Ensemble of Ground Motions Simulation Based on Discrete Stationary Wavelet Transform

Simulation of earthquake ground motion was a hot topic for structure seismic response analysis. According to the problems in simulating ground motion history with harmony superposition method, such as more interference of human factors and simulated ground motion history didn’t have frequency non-stationary characteristic, a novel method of ground motion simulation based on stationary discrete wavelet transform was presented. Using stationary discrete wavelet transform, the parent ground motion history was decomposed into different frequency bands, and the coefficients were modified. Using inverse stationary discrete wavelet transform, an ensemble of ground motions were simulated whose statistics closely resemble those of the parent history. Through a numerical example, the statistic characteristics of simulated histories were compared with the original values, and the feasibility and correctness of presented method was illustrated.