Broadband Strong Ground Motion Research Articles

Prediction of Regional Broadband Strong Ground Motions Using a Teleseismic Source Model of the 18 April 2014 Mw 7.3 Papanoa, Mexico, Earthquake

Prediction of Regional Broadband Strong Ground Motions Using a Teleseismic Source Model of the 18 April 2014 Mw 7.3 Papanoa, Mexico, Earthquake

Causes and Remedies of Fourier Amplitude Sags at Intermediate Frequencies for Simulating Broadband Strong Ground Motions Using Stochastic Green's Function Methods

Causes and Remedies of Fourier Amplitude Sags at Intermediate Frequencies for Simulating Broadband Strong Ground Motions Using Stochastic Green's Function Methods

Modeling of Subsurface Velocity Structures from Seismic Bedrock to Ground Surface in the Tokai Region, Japan, for Broadband Strong Ground Motion Prediction

For sophistication of strong ground motion prediction in terms of disaster mitigation, one of the principal issues is to model subsurface velocity structures so that characteristics of earthquake ground motions can be reproduced in the broadband range 0.1 Hz to 10 Hz. In recent years, subsurface structures have been modeled in sedimentary layers on seismic bedrock for a few regions of Japan, in a national project. In this study, subsurface velocity structures were modeled from seismic bedrock to the ground surface for the Tokai region. These models were constructed in accordance with the subsurface velocity structure modeling scheme published by the Headquarters for Earthquake Research Promotion. To begin with, initial models were constructed based on existing bore-hole data, geological information, etc. Next, they were improved based on results of microtremor explorations which had been conducted in recent years. It was found that the new model had different characteristics to the conventional model. This paper will present the modeling process and characteristics of distribution maps for velocity structures and amplification index.

Revisiting the 1995 MW 6.4 Aigion, Greece, earthquake: Simulation of broadband strong ground motion and site response analysis

The 1995 MW 6.4 Aigion earthquake is one of the largest and most destructive seismic events that have occurred in Greece over the past few decades. The ground shaking in the near-fault region was recorded by a strong-motion accelerograph in the city of Aigion, at a distance of about 16km from the epicenter. The recorded horizontal ground acceleration exceeded 0.5g, whereas the horizontal components of ground velocity exhibited pulse-like motions of large amplitude. These ground-motion characteristics have been attributed to forward rupture directivity combined with the effects of soil and topography. In this article, broadband synthetic ground motions are generated at selected locations and at a dense grid of observation points extending over the causative fault of the 1995 Aigion earthquake using a hybrid deterministic-stochastic method. The low-frequency components of the synthetic ground motion are simulated using the discrete wavenumber method and the generalized transmission and reflection coefficient technique, whereas the high-frequency components of the synthetic ground motion are generated using the stochastic modeling approach and the specific barrier model. The two independently derived ground-motion components are then combined using matched filtering at a crossover frequency of 2Hz to generate broadband ground-motion time histories and response spectra. The effects of soil and topography on the simulated ground motion in the city of Aigion are also investigated through site response analysis. In addition, the strong motion recorded at Aigion is corrected for crustal anisotropy using the cross-correlation technique, thus further enhancing the alignment of recorded and synthetic ground-motion time histories. Finally, the synthetic ground motions are compared with ground-motion estimates obtained from observed geotechnical damage, USGS ShakeMaps, and ground-motion prediction equations.

Simulation of broad-band strong ground motion for a hypothetical Mw 7.1 earthquake on the Enriquillo Fault in Haiti

Simulation of broad-band strong ground motion for a hypothetical Mw 7.1 earthquake on the Enriquillo Fault in Haiti

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

The main motivation for this study was the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in the Marmara Sea and the disaster risk around the Marmara region, especially in Istanbul. This study provides the results of a physically based probabilistic seismic hazard analysis (PSHA) methodology, using broadband strong ground motion simulations, for sites within the Marmara region, Turkey, that may be vulnerable to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We included the effects of all considerable-magnitude earthquakes. To generate the high-frequency (0.5–20 Hz) part of the broadband earthquake simulation, real, small-magnitude earthquakes recorded by a local seismic array were used as empirical Green’s functions. For the frequencies below 0.5 Hz, the simulations were obtained by using synthetic Green’s functions, which are synthetic seismograms calculated by an explicit 2D/3D elastic finite difference wave propagation routine. By using a range of rupture scenarios for all considerable-magnitude earthquakes throughout the PIF segments, we produced a hazard calculation for frequencies of 0.1–20 Hz. The physically based PSHA used here followed the same procedure as conventional PSHA, except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes, and this approach utilizes the full rupture of earthquakes along faults. Furthermore, conventional PSHA predicts ground motion parameters by using empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitudes of earthquakes to obtain ground motion parameters. PSHA results were produced for 2, 10, and 50 % hazards for all sites studied in the Marmara region.

Hybrid Ground Motion Simulation for the 2013 ML 6.4 Ruisui, Taiwan Earthquake

The 2013 M_L 6.4 Ruisui earthquake struck a seismic gap around the northern part of the Longitudinal Valley where rare earthquakes have occurred for at least two decades. Seismic data with different frequency bands connote a diverse scale of source characteristics. The slip model derived by a previous study using long-period seismic data provided us with the preliminary earthquake source properties in low-frequency energy radiation. However, the high-frequency part of the seismic energy needs to be considered for the strong motions in the comprehensive frequency band. As a case study, we carried out broadband strong motion simulations through the hybrid scheme, which simulated waveforms combining the low-frequency motions (frequency-wavenumber integration method) and high-frequency motions (empirical Green's function method) to reveal the strong ground motion and source characteristics of the 2013 Ruisui earthquake. The results show that even though the local structure is complicated this hybrid simulation can effectively rebuild the overall broadband strong ground motion characteristics for the 2013 Ruisui earthquake. Additional study issues are required to better understand the nature of localized high peak ground acceleration and the related seismic hazards for future earthquakes.

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 Hybrid Approach for Broadband Simulations of Strong Ground Motion: The Case of the 2008 Iwate–Miyagi Nairiku Earthquake

Abstract We developed a hybridization code that merges the full‐wave low‐frequency (LF) signals with stochastic high‐frequency (HF) synthetics to simulate broadband strong ground motion for engineering applications. The approach is applied to reproduce, within the known source and structure constraints, the Kiban–Kyoshin network (KiK‐net) and Kyoshin net (K‐NET) accelerometric data recorded during the 2008 Iwate–Miyagi Nairiku earthquake ( M w 7.0). The results show that our approach is able to simulate satisfactorily the observed waveforms and the related response spectra over the broadband frequency range. We estimated the effects of the hybridization in the peak and spectral parameters through the goodness‐of‐fit criteria: the overall fit improves (∼15%–20%) when, instead of full‐wave calculated seismograms, we use the low‐pass filtered recordings, showing that a good match at LFs is fundamental to obtain reliable and consistent results even in the HF band. Peak ground velocities are less affected than accelerations by the inclusion of the HF contribution and are well reproduced by our method; peak ground accelerations show larger discrepancies due to the intrinsic characteristics of the stochastic model and the small‐scale heterogeneity that affect the seismic radiation and propagation at HFs. Nevertheless, simulated signals reproduce the observed ones fairly well, and an acceptable match is also found in the comparison of the spectral responses. Online Material: Figures showing the COMPEX merging procedure, comparison of recorded and simulated response spectra, and comparison of recorded and synthetic broadband signals; and tables of source parameters, 1D velocity model, and matching frequencies.

PSHA for Broad-Band Strong Ground-Motion Hazards in the Saronikos Gulf, Greece, from Potential Earthquake with Synthetic Ground Motions

We perform a probabilistic seismic hazard analysis (PSHA) for broad-band strong ground motion within the Saronikos Gulf region, Greece, from potential earthquakes along the 30 km long Aigina fault in the northern part of the Gulf. We perform the PSHA utilizing empirical Green’s functions (EGFs) merged with synthetic Green’s functions (SGFs) along with models of finite rupture in place of standard “attenuation relations.” Our approach considers all significant magnitudes for PSHA and full broadband ground motion simulations. Calculations are source and site specific, and could reduce uncertainties in estimating standard engineering parameters. We use a range of rupture scenarios for all significant magnitude earthquakes along the fault. The hazard calculation is for frequencies 0.0– 15.0 Hz. Recordings of small earthquakes from an onshore/offshore local seismic array were used as EGFs for frequencies of 1.5–15.0 Hz, the finite difference code E3D was utilized to synthesize SGFs for frequencies 0.0–1.5 Hz, and an algorithm for merging the EGFs with SGFs was developed. The full-waveform calculations are important for non-linear dynamic analysis of structures in the coastal zone and potential hazard to long period structures. Results of proposed PSHA identify 2%, 10%, and 50% hazard at the selected sites of Saronikos Gulf.Finally, we compare our PSHA results to those obtained by standard practice which involves prediction equations (GMPEs) recently developed in the Next Generation Attenuation (NGA) project and empirical predictive attenuation relations proposed for Greece. We believe that differences with the NGA results are due to site- and source-specific information utilized in this study, and incorporation of this information may significantly reduce the uncertainty in seismic hazard calculations.

Scenario Source Models and Strong Ground Motion for Future Mega‐earthquakes: Application to Lima, Central Peru

The 2011 moment magnitude ( M w) 9.0 Tohoku‐Oki Japan earthquake occurred in a region where giant megathrust earthquakes were not expected. This earthquake proved the difficulty in assessing seismic hazard by relying mainly on information from historical and instrumental seismicity. To help improve the seismic‐hazard assessment for such rare events, we propose a methodology to estimate the slip distribution of future megathrust earthquakes based on a model of interseismic coupling distribution in subduction margins, as well as information of historical earthquakes, and apply the method to the central Peru region, Lima. The slip model obtained from geodetic data represents the large scale features of asperities within the megathrust, which is appropriate for simulation of long‐period waves and tsunami modeling. For the simulation of a broadband strong ground motion, we add small scale heterogeneities to the source slip to be able to simulate high frequencies. To achieve this purpose, we propose broadband source models constructed by adding short‐wavelength slip distributions obtained from a Von Karman power spectral density function, to the slip model inferred from interseismic geodetic data. Using these slip models and assuming several hypocenter locations, we calculate a set of strong ground motions for Lima and incorporate site effects obtained from microtremors surveys and geotechnical data. Our simulated average pseudospectral accelerations (period 0.3 s) are above ![Graphic][1] for wide areas in Lima, which may be critical in terms of damage of low‐ to midrise masonry and reinforced concrete buildings, which characterize the majority of buildings in Lima. [1]: /embed/inline-graphic-1.gif

Behavior of a seismically isolated bridge crossing a fault rupture zone

The effect of the fault rupture zone traversing a seismically isolated bridge is investigated utilizing a finite element model of a section of the Bolu Viaduct and a set of synthetic broadband strong ground motions simulated for the Bolu Viaduct site due to the 1999 Duzce earthquake. Both the original and a potential retrofit seismic isolation system designs are considered in the analyses. The results show double isolation system demands when fault crossing is considered, as compared to the case where fault crossing is ignored. The pier drift demands, however, remain comparable in both cases. Furthermore, the location of fault crossing along the bridge length, as well as the fault orientation with respect to the bridge longitudinal direction are shown to influence substantially the response of the seismically isolated bridge. Isolation system permanent displacements are greatly influenced by the restoring force capability of the isolation system when fault crossing effects in the excitations are ignored. In the case of fault crossing, the permanent displacements of the isolation system are dominated by the substantial permanent tectonic displacement along the fault trace which is imposed upon the structure. The results of this study contribute to developing a better understanding of how seismically isolated bridges respond when traversed by fault rupture zones. The lack of analyses and design guidelines for bridges crossing faults in international standards renders this study a useful reference for the profession.

Improving seismotectonics and seismic hazard assessment along the San Ramón Fault at the eastern border of Santiago city, Chile

The San Ramón Fault is an active west-vergent thrust fault system located along the eastern border of the city of Santiago, at the foot of the main Andes Cordillera. This is a kilometric crustal-scale structure recently recognized that represents a potential source for geological hazards. In this work, we provide new seismological evidences and strong ground-motion modeling from hypothetic kinematic rupture scenarios, to improve seismic hazard assessment in the Metropolitan area of Central Chile. Firstly, we focused on the study of crustal seismicity that we relate to brittle deformation associated with different seismogenic fringes in the main Andes in front of Santiago. We used a classical hypocentral location technique with an improved 1D crustal velocity model, to relocate crustal seismicity recorded between 2000 and 2011 by the National Seismological Service, University of Chile. This analysis includes waveform modeling of seismic events from local broadband stations deployed in the main Andean range, such as San José de Maipo, El Yeso, Las Melosas and Farellones. We selected events located near the stations, whose hypocenters were localized under the recording sites, with angles of incidence at the receiver <5° and S–P travel times <2 s. Our results evidence that seismic activity clustered around 10 km depth under San José de Maipo and Farellones stations. Because of their identical waveforms, such events are interpreted like repeating earthquakes or multiplets and therefore providing first evidence for seismic tectonic activity consistent with the crustal-scale structural model proposed for the San Ramón Fault system in the area (Armijo et al. in Tectonics 29(2):TC2007, 2010). We also analyzed the ground-motion variability generated by an M w 6.9 earthquake rupture scenario by using a kinematic fractal k −2 composite source model. The main goal was to model broadband strong ground motion in the near-fault region and to analyze the variability of ground-motion parameters computed at various receivers. Several kinematic rupture scenarios were computed by changing physical source parameters. The study focused on statistical analysis of horizontal peak ground acceleration (PGAH) and ground velocity (PGVH). We compared the numerically predicted ground-motion parameters with empirical ground-motion predictive relationships from Kanno et al. (Bull Seismol Soc Am 96:879–897, 2006). In general, the synthetic PGAH and PGVH are in good agreement with the ones empirically predicted at various source distances. However, the mean PGAH at intermediate and large distances attenuates faster than the empirical mean curve. The largest mean values for both, PGAH and PGVH, were observed near the SW corner within the area of the fault plane projected to the surface, which coincides rather well with published hanging-wall effects suggesting that ground motions are amplified there.

Combining a Kinematic Fractal Source Model with Hybrid Green's Functions to Model Broadband Strong Ground Motion

Abstract A hybrid empirical method is proposed to simulate broadband strong ground motion that combines a kinematic complex source model with both numerical and empirical Green’s functions. The kinematic approach is based on a composite source model description where subevents are generated using a fractal distribution of sizes. The subevents are set up with a size‐dependent rise time. Each elementary source is described as a crack‐type slip model that starts radiating when the rupture front reaches the nucleation point located randomly inside a size‐dependent nucleation region. The synthetic acceleration spectra follow the ω 2 model, and the spectral amplitudes are scaled by a frequency‐dependent directivity coefficient. In this study, the hypothesis of constant stress drop of subevents is released to better model the high‐frequency level radiated by the source. Taking advantage of small‐magnitude events, synthetic seismograms are computed using hybrid Green’s functions (HGF) to model the impulsive response of the medium. The procedure computes HGF for each subfault combining the numerical low‐frequency and the empirical high‐frequency Green’s functions with appropriate amplitude and phase correction (geometrical spreading and time delays due to the S ‐wave travel‐time propagation). This methodology is applied to simulate the strong ground motions recorded during the 1997 M w 5.9 Yamaguchi‐Ken, Hokubu, Japan, earthquake. Some of the finite‐source rupture parameters (e.g., rupture velocity, asperity size, and seismic moment) were chosen according to previously published studies conducted on this event. Only random generation of k −2 composite slip distributions was allowed ( k being the radial wavenumber), to model heterogeneous slip while mimicking the main asperity size and location imaged. Comparisons of predicted and observed strong‐motion characteristics show that predictions are largely improved, when both HGF and variable stress drop of subevents are used.

Finite-Fault Simulation of Broadband Strong Ground Motion from the 2010 Mw 7.0 Haiti Earthquake

Abstract Because of the socioeconomic environment in the small island nation of Haiti, no seismic recording stations were operating in the source region at the time of the 2010 M w 7.0 earthquake. The lack of strong motion instruments has hindered the estimation of the amplitude, duration, and frequency content of the ground shaking caused by the seismic event. In this study, synthetic broadband strong ground motions are generated in the vicinity of the 2010 Haiti earthquake. The low‐frequency components of the synthetic motions are simulated using a slip model compatible with seismological observations, geologic field data, and space geodetic measurements. The computations are carried out using the discrete wavenumber representation method and the generalized transmission and reflection coefficient technique. The high‐frequency ground‐motion components are generated using the stochastic modeling approach and the specific barrier model. The two independently derived ground‐motion components are subsequently combined using matched filtering at a crossover frequency of 1 Hz to generate broadband ground‐motion time histories and response spectra for the city of Port‐au‐Prince and other sites in the vicinity of the earthquake. Finally, the synthetic strong ground motions are compared against peak ground‐motion estimates inferred from the U.S. Geologic Survey ShakeMap of peak ground accelerations, ground‐motion prediction equations, and observed structural damage. The synthetic time histories and response spectra generated in this study should be seen as plausible, but not necessarily unique, ground motions that capture the primary features of the 2010 Haiti earthquake.

Source model for strong ground motion generation in the frequency range 0.1–10 Hz during the 2011 Tohoku earthquake

The source model of the 2011 Tohoku earthquake, which is composed of four strong motion generation areas (SMGAs), is estimated based on the broadband strong ground motion simulations in the frequency range 0.1–10 Hz using the empirical Green’s function method. Two strong motion generation areas are identified in the Miyagi-oki region west of the hypocenter. Another two strong motion generation areas are located in the Fukushima-oki region southwest of the hypocenter. The strong ground motions in the frequency range 0.1–10 Hz along the Pacific coast are mainly controlled by these SMGAs. All the strong motion generation areas exist in the deeper portion of the source fault plane. The stress drops of the four SMGAs range from 6.6 to 27.8 MPa, which are similar to estimations for past M 7-class events occurring in this region. Compared with the slip models and aftershock distributions of past interplate earthquakes in the Miyagi-oki and Fukushima-oki regions since the 1930s, the SMGAs of the 2011 Tohoku earthquake spatially correspond to the asperities of M 7-class events in 1930s. In terms of broadband strong ground motions, the 2011 Tohoku earthquake is not only a tsunamigenic event with a huge coseismic slip near the trench but is also a complex event simultaneously rupturing pre-existing asperities.

Source model of the 2007 Noto-Hanto earthquake (Mw 6.7) for estimating broad-band strong ground motion

AbstractA source model for estimating broad-band ground motions from the 2007 Noto-Hanto earthquake (Mw6.7) is estimated from a comparison of the observed records of the mainshock and synthesized motions based on the characterized asperity model using the empirical Green’s function method. The observed records of aftershocks used as the empirical Green’s functions are carefully selected to have almost the same radiation characteristics and source distance as the asperities of the mainshock. The best-fit source model consists of two asperities of different size. A large one is located just above the hypocenter, with an area of 6.3×6.3 km2and stress drop of about 26 MPa. A smaller one is located north-east of the large one, with an area of 3.6×3.6 km2and stress drop of about 10 MPa. The stress drop of the large one is about twofold higher than the average values of inland crustal earthquakes so far estimated, while that of smaller one is almost average. We found that the remarkable directivity pulses from the source model struck the northern part of the Noto peninsula, causing heavy damage in some towns there.

Development of attenuation relation for the near fault ground motion from the characteristic earthquake

A composite source model has been used to simulate a broadband strong ground motion with an associated fault rupture process. A scenario earthquake fault model has been used to generate 1000 earthquake events with a magnitude of Mw8.0. The simulated results show that, for the characteristic event with a strike-slip faulting, the characteristics of near fault ground motion is strongly dependent on the rupture directivity. If the distance between the sites and fault was given, the ground motion in the forward direction (Site A) is much larger than that in the backward direction (Site C) and that close to the fault (Site B). The SH waves radiated from the fault, which corresponds to the fault-normal component plays a key role in the ground motion amplification. Corresponding to the sites A, B, and C, the statistical analysis shows that the ratio of their aPG is 2.15:1.5:1 and their standard deviations are about 0.12, 0.11, and 0.13, respectively. If these results are applied in the current probabilistic seismic hazard analysis (PSHA), then, for the lower annual frequency of exceedance of peak ground acceleration, the predicted aPG from the hazard curve could reduce by 30% or more compared with the current PSHA model used in the developing of seismic hazard map in the USA. Therefore, with a consideration of near fault ground motion caused by the rupture directivity, the regression model used in the development of the regional attenuation relation should be modified accordingly.

A Fast and Efficient Simulation of the Far-Fault and Near-Fault Earthquake Ground Motions Associated with the June 17 and 21, 2000, Earthquakes in South Iceland

The two Mw 6.5 earthquakes on June 17 and 21, 2000, respectively, in the populated South Iceland Seismic Zone (SISZ) significantly augmented the Icelandic database of strong ground motions, and several strong velocity pulses were recorded at near-fault sites. The strong motions are interpreted via the Specific Barrier Model (SBM) and a mathematical model of near-fault velocity pulses. The data indicates self-similar source scaling and significantly greater attenuation of seismic waves than in other interplate regions. Through inversion of the data a new attenuation function for the SISZ has been adopted, which results in unbiased simulations. For the first time, the characteristics of the recorded near-fault pulses have been identified and compared to the worldwide database of such records. The SBM and the near-fault pulse model combine naturally in a fast and efficient synthesis of realistic, broad-band strong ground motions in the far-fault and near-fault region. Such simulations are showcased for the June 2000 earthquakes and indicate that the modeling approach adopted in this study is an effective tool for the estimation of realistic earthquake ground motions in the SISZ.

広帯域強震動評価のための堆積層深部地盤速度構造のモデル化 -大阪堆積盆地のサイト増幅スペクトルに着目して-

広帯域強震動評価のための堆積層深部地盤速度構造のモデル化 -大阪堆積盆地のサイト増幅スペクトルに着目して-