Damped Pseudospectral Acceleration Research Articles

A model for estimating horizontal aftershock ground motions for active crustal regions

Inconsistent observations on the characteristics of ground motions from aftershocks have been found, while there is increasing attention to effects of aftershock ground motions on structural behaviors. This study examines differences in ground motions from main shock and aftershock earthquakes using the NGA-West2 database, and propose an empirical model to estimate the average horizontal components of peak ground acceleration (PGA), and peak ground velocity (PGV), and 5% damped pseudo spectral acceleration (PSA) at various spectral periods of aftershock earthquakes for tectonically active crustal regions, as a function of aftershock to main shock magnitude ratio, distance ratio, and time-averaged shear-wave velocity in the upper 30m of soil deposits (VS30). Spectral accelerations from aftershock earthquakes are smaller than those from main shock earthquakes given the same magnitude, especially at short periods. Performance of the proposed model is evaluated using a mixed-effects residuals analysis. Period-dependent standard deviation of residuals is also presented.

A comparative analysis of site-specific response spectral amplification models

In the framework of the Seismic Hazard Harmonization in Europe (SHARE) project, the Swiss Seismological Service (SED) has performed an evaluation of two procedures developed to produce soil amplification models for 5% damped pseudo-spectral acceleration response spectra, each using different parameters to describe the soil properties. The goal of the work presented here is to evaluate the statistical consistency of the methods, with particular regard to their applicability to engineering practice. Additionally, we compare the results with those from a methodology internally developed by the SED, which is based on spectral modeling of ground motion using the quarter-wavelength approximation to parameterize soil conditions. Soil amplification is computed with respect to reference rock condition as defined for the probabilistic seismic hazard assessment performed during the SHARE project.For the comparison, a residual analysis was performed between the computed soil-amplification functions from the three different methodologies, over a number of selected sites spanning different soil classes and ground motion levels. The analysis of the average residuals of these functions is useful to highlight the main differences between the proposed approaches, with special regard to the impact of soil resonances and anelastic attenuation within different frequency bands.The assessment was performed on a group of 88 selected stations of the Japanese KiKNet strong-motion network, for which complete logs of the shear-wave velocity profiles are available, in addition to a significant number of earthquake recordings. In a first step, average residuals were computed. Subsequently, amplification variability related to soil classes was investigated. The target of this second step was to perform the comparison by separately analyzing the impact of different soil and velocity classes, according to a soil-classification scheme proposed by Aristotle University of Thessaloniki (AUTH). In this paper the main results of these investigations are summarized and, when applicable, an interpretation of our findings is given.

Intensity measures that reduce collapse capacity dispersion of P-delta vulnerable simple systems

The study evaluates two alternative seismic intensity measures (IMs) that reduce the collapse capacity dispersion of inelastic non-degrading single-degree-of-freedom (SDOF) systems vulnerable to the P-delta effect. This dispersion of collapse capacity is caused by record-to-record variability, which refers to frequency content variation of the ground motions used in the dynamic analyses. This reduction (of dispersion) is achieved utilizing efficient elastic pseudo-spectral acceleration based IMs. The first set of evaluated IMs is based on the spectral pseudo-acceleration averaged in a certain period interval between the structural period and an elongated period. The “optimal” lower bound of the period interval corresponds to the structural period of vibration, since naturally in an SDOF system no higher modes effects do exist. The “optimal” upper bound of the period interval for averaging, referred to as elongated period, is found to be 1.6 times the system period. The second IM considered in the study is the 5 % damped spectral pseudo-acceleration at the system period in the presence of gravity loads, which is a single target IM. The most widely accepted IM, the 5 % damped pseudo-spectral acceleration at the system period without P-delta, serves as the benchmark IM. The results show that both proposed IMs lead to a reduction of the collapse capacity dispersion compared to the benchmark IM outcomes. The IM based on the averaged spectral acceleration of the “optimal” period interval is more efficient up to a negative post-yield stiffness ratio of 0.45, while the single target IM based on the system period in the presence of gravity loads is superior for extreme negative post-yield stiffness ratios larger than 0.45. Additionally, the sufficiency and the scaling robustness property of the considered IMs with respect to the natural logarithm of the record-dependent individual collapse capacities is discussed for a wide range of structural configurations.

Probabilistic Seismic Hazard Model of West Bengal, India

We deliver a next-generation Probabilistic Seismic Hazard model of West Bengal based on improved seismogenic source characterization considering both the Layered Polygonal sources & Tectonic sources in the hypocentral depth range of 0–25 km & 25–70 km, seismic local-specific site condition, and adaption of appropriate region specific ground motion prediction equations in a logic tree framework. The surface consistent Probabilistic seismic hazard distribution in terms of Peak Ground Acceleration (PGA) & 5% damped Pseudo Spectral Acceleration (PSA) at different time periods for 10% probability of exceedance in 50 years have been generated and the design response spectra computed.

Ground‐Motion Prediction Equations for Central and Eastern North America

A new ground‐motion prediction equation (GMPE) model for central and eastern North America (CENA) is presented. The Graizer 2016 (G‐16) model is based on the Next Generation Attenuation‐East (NGA‐East) database for this horizontal peak ground acceleration and 5% damped pseudospectral acceleration RotD50 component (Goulet et al. , 2014). The CENA database is not sufficient for creating purely empirical GMPE with recordings covering mostly a range of moment magnitudes M <6.0 and a limited number of near‐fault recordings. The functional forms of the G‐16 model are derived from filters representing a particular physical phenomenon affecting the seismic‐wave radiation from the source, following the approach developed by Graizer and Kalkan (2007, 2009, and 2011) for active tectonic environment. Main changes in the functional forms for CENA relative to the western United States model (Graizer and Kalkan, 2015) are a shift of maximum frequency of the acceleration response spectrum (RS) toward higher frequencies and an increase in RS amplitudes at high frequencies. The developed site correction is based on multiple runs of representative V S 30 profiles through SHAKE‐type equivalent‐linear codes. Site amplifications are calculated relative to the hard‐rock definition used in nuclear industry ( V S =2800 m/s). The number of model predictors is limited to a few measurable parameters such as moment magnitude M , closest distance to fault rupture plane R rup, V S 30, and anelastic attenuation factor Q . Incorporating Q as an input parameter allows adjustments based on the regional crustal properties. The model is applicable for the stable continental regions and covers the following range: 4.0≤ M ≤8.5, 0≤ R rup≤1000 km, 450≤ V S 30≤2800 m/s, and frequencies 0.1≤ f ≤100 Hz.

Summary of the GK15 Ground‐Motion Prediction Equation for Horizontal PGA and 5% Damped PSA from Shallow Crustal Continental Earthquakes

We present a revised ground‐motion prediction equation (GMPE) for computing medians and standard deviations of peak ground acceleration (PGA) and 5% damped pseudospectral acceleration (PSA) response ordinates of the horizontal component of randomly oriented ground motions to be used for seismic‐hazard analyses and engineering applications. This GMPE is derived from the expanded Next Generation Attenuation (NGA)‐West 1 database (see [Data and Resources][1]; Chiou et al. , 2008). The revised model includes an anelastic attenuation term as a function of quality factor ( Q ) to capture regional differences in far‐source (beyond 150 km) attenuation, and a new frequency‐dependent sedimentary‐basin scaling term as a function of depth to the 1.5 km/s shear‐wave velocity isosurface to improve ground‐motion predictions at sites located on deep sedimentary basins. The new Graizer–Kalkan 2015 (GK15) model, developed to be simple, is applicable for the western United States and other similar shallow crustal continental regions in active tectonic environments for earthquakes with moment magnitudes ( M ) 5.0–8.0, distances 0–250 km, average shear‐wave velocities in the upper 30 m ( V S 30) 200–1300 m/s, and spectral periods ( T ) 0.01–5 s. Our aleatory variability model captures interevent (between‐event) variability, which decreases with magnitude and increases with distance. The mixed‐effect residuals analysis reveals that the GK15 has no trend with respect to the independent predictor parameters. Compared to our 2007–2009 GMPE, the PGA values are very similar, whereas spectral ordinates predicted are larger at T <0.2 s and they are smaller at longer periods. [1]: #sec-21

Applicability of the Site Fundamental Frequency as aVS30Proxy for Central and Eastern North America

We introduce a new proxy measure for V S 30 (time‐averaged shear‐wave velocity in the upper 30 m) for central and eastern North America (CENA). The new proxy is the site fundamental frequency ( f peak), measured from the horizontal‐to‐vertical (H/V) spectral ratios of recorded ground motion (or ambient noise). In this study, H/V spectral ratios are obtained from 5% damped pseudospectral acceleration (PSA) from seismograph stations in CENA using the Next Generation Attenuation‐East (NGA‐East) database. We correlate the measured V S 30 values at recording stations with the corresponding f peak values to obtain a predictive relationship for V S 30. The uncertainty of the V S 30 estimate using the f peak‐based model is small (0.14log10 units) in comparison to that for the proxy‐based methods (e.g., topographic slope and surface geology proxies) used in the NGA‐East database (0.25log10 units). However, values of f peak can be obtained for only about 23% of the NGA‐East recording stations due to data and site‐type limitations. Reducing the error in V S 30 estimates can potentially reduce the variability of ground‐motion prediction equations (GMPEs). To test this hypothesis, we use the f peak‐based V S 30 estimates and select one of the proponent NGA‐East GMPE models. For a selected database, we are able to reduce the GMPE variability ( σ ) by 3% on average, for PSA at 1–10 Hz, just using the f peak‐based proxy to estimate V S 30. Greater variability reductions could be achieved by replacing V S 30 with improved site characterization parameters, including f peak, in the GMPEs.

Estimation of Moment Magnitude and Stress Parameter from ShakeMap Ground‐Motion Parameters

We describe an efficient method to determine moment magnitude and stress parameter in near real time, in the immediate aftermath of a small‐to‐moderate earthquake ( M ∼3–6), from ShakeMap ground‐motion parameters (5% damped pseudospectral acceleration) at 1 Hz, 0.33 Hz, 10 Hz and/or peak ground acceleration. The methodology is based on relating ShakeMap parameters to source and attenuation parameters within the context of a generic stochastic point‐source model, to provide an event‐specific ground‐motion prediction equation (GMPE) that will reliably predict amplitudes. It is an approach that has been optimized for applications in regions with sparse networks; an example is provided for southern Ontario. In brief, we initially develop a simulation‐guided generic GMPE model based on the available database in the region. We derive the applicable regional anelastic attenuation, stress parameter, and site amplification models. Then, using the estimated regional models, we show how to invert ShakeMaps parameters to estimate moment magnitude and stress parameter in near real time, to define an event‐specific GMPE for an event that just happened. The event‐specific GMPE can be used to provide robust, calibrated ShakeMaps that are fully consistent with ground‐motion observations.

Regionally Adjustable Generic Ground‐Motion Prediction Equation Based on Equivalent Point‐Source Simulations: Application to Central and Eastern North America

Abstract We develop a generic ground‐motion prediction equation (GMPE) that can be adjusted for use in any region by modifying a few key model parameters. The basis of the GMPE is an equivalent point‐source simulation model whose parameters have been calibrated to empirical data in California, in such a way as to determine the decoupled effects of basic source and attenuation parameters on ground‐motion amplitudes. We formulate the generic GMPE as a function of magnitude, distance, stress parameter, geometrical spreading rate, and anelastic attenuation. This provides a fully adjustable predictive model, allowing users to calibrate its parameters using observed motions in the target region. We also include an empirical calibration factor to account for residual effects that are different from and/or missing in simulations compared to observed motions in the target region. As an example, we show how the generic GMPE can be adjusted for use in central and eastern North America (CENA), and calibrated with the Next Generation Attenuation‐East database. We provide median predictions of ground motions in CENA for average horizontal‐component peak ground motions and 5% damped pseudospectral acceleration (periods up to T =10 s), for magnitudes M 3–8 and distances up to 600 km.

Preliminary Evaluation of Ground Motions from Earthquakes in Alberta

Between 9 September 2013 and 22 January 2015, more than 900 seismic events in local magnitude ( M L) range 1–4 were detected and located in near‐real time by the new TransAlta/Nanometrics network in western Alberta, which commenced operation in the fall of 2013. The network comprises 27 three‐component broadband seismograph stations, located as shown in Figure 1, which act in cooperation with other real‐time seismograph stations operated by the Alberta Geological Survey (AGS) (Stern et al. , 2011) and the Geological Survey of Canada (GSC). There are additional campaign‐mode stations in the Canadian Rockies and Alberta Network (CRANE) network operated by the University of Alberta (Gu et al. , 2011). Figure 1. Locations of stations and study events in Alberta. Events that are considered to be blasts are designated by an x within the magnitude symbol. Note that the deformation front that marks the boundary of the Rocky Mountains is distinguishable by topography. In this study, we compile and analyze a ground‐motion database of 5% damped pseudospectral acceleration (PSA) from the signals recorded on the TransAlta/Nanometrics stations in order to gain an initial understanding of overall ground‐motion source, attenuation, and site characteristics in the region. A catalog of events is provided on www.inducedseismicity.ca (last accessed May 2015); the locations and initial magnitudes of events were obtained by Nanometrics (www.nanometrics.ca; last accessed May 2015). We processed the recorded time series as described in Assatourians and Atkinson (2010). Briefly, the velocity time series are corrected for glitches and trends, then filtered and corrected for instrument response in the frequency domain. Differentiation to generate acceleration time series is done in the frequency domain before conversion back to the time domain. Horizontal and vertical peak ground velocity and peak ground acceleration values are computed from peak amplitudes of instrument‐corrected time series, and 5% damped …

Seismic hazard assessment for Yanbu metropolitan area, western Saudi Arabia

The stochastic method is used to predict ground motions for Yanbu metropolitan area which has been affected byseveral earthquakeswiththe maximum magnitudeof6.8in 1121 AD. The stochastic method has been used for simulating the time domain history for the peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground dis- placement (PGD) at Yanbu metropolitan area. In addition, the response spectra at 3, 5, and 10 % of the damped pseudo-spectral acceleration (PSA) have been calculated at Al-Majd Sporting Club, Al-Maktabah, and Al-Shate Secondary School sites within the Yanbu metropolitan area. The results show that the values of PGA range from 137 to 388 cm/s 2 , PGV values vary from 8.96to 25.5 cm/s, and PGD values range from 6.7 to 20.9 cm. The values of pseudo- spectral acceleration and predominant period are 974.53 cm/ s 2 (with 5 % damping) at 0.14 s for Al-Majd Sporting Club, 487.06cm/s 2 at 0.19s for Al-Maktabah site, and 700.83cm/s 2 at 0.14 s for Al-Shate Secondary School. It is cleared that the values of ground motion parameters are amplified due to the presence of thick sections of very soft to soft sediments to more than six times those of the hard rocks. Furthermore, the estimated predominant periods from this study are corre- lated well with that of multichannel analysis of surface wave (MASW) approach. These results should be taken into account during design and construction of civil engineering structures within the Yanbu metropolitan area.

Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification

We present a new set of Ground Motion Prediction Equations (GMPEs) for horizontal Peak Ground Acceleration, Peak Ground Velocity, and 5 % damped pseudo-spectral acceleration (PSA), developed for the San Jacinto Fault Zone (SJFZ) area. Besides using these equations to quantify seismic shaking in the area, the results allow us to examine the physics and local properties controlling the observed ground motions. The analyzed dataset includes ~30,000 observations from ~800 events spanning a magnitude range of 1.5 < M < 6.0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km. The local GMPE is developed for the SJFZ by applying classical regression techniques with predictive variables that include first distance and magnitude, and then site characteristics, rupture directivity, and fault zone amplification. The significance of these effects is determined by measuring the uncertainty-reduction of the GMPE due to each factor. The results show that, in contrast to many regional studies, traditional site characteristic has a relatively minor effect on peak amplitudes in our study area. However, rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events. The dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance, using the ground-motion dataset during the regression analysis process. The obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations, known from other studies, and predictions for bimaterial ruptures in the trifurcation area of the SJFZ. Fault zone amplification is a second important factor, showing strong impact on the peak ground motion values, with increasing role for the lower frequency range (<10 Hz) examined in the 5 % damped PSA values. We also observe signatures of large amplitude-variances, which indicate additional source-related control on the distribution of amplitudes (besides rupture directivity) for aftershocks close in time and location to the M L 5.1 earthquake of March 2013. Using the full set of records we present the most complete set of GMPEs for the SJFZ area, including a higher-amplitude prediction for regions in the direction of rupture.

A Stochastic Earthquake Ground‐Motion Prediction Model for the United Kingdom

Low‐seismicity regions such as the United Kingdom (UK) pose a challenge for seismic hazard analysis in view of the limited amount of locally recorded data available. In particular, ground‐motion prediction is faced with the problem that most of the instrumental observations available have been recorded at large distances from small earthquakes. Direct extrapolation of the results of regression on these data to the range of magnitudes and distances relevant for the seismic hazard analysis of engineered structures generally leads to unsatisfactory predictions. The present study presents a new ground‐motion prediction equation (GMPE) for the UK in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and 5% damped pseudospectral acceleration (PSA), based on the results of numerical simulations using a stochastic point‐source model calibrated with parameters derived from local weak‐motion data. The predictions from this model are compared with those of previous GMPEs based on UK data, other GMPEs derived for stable continental regions (SCRs), as well as recent GMPEs developed for the wider European area.

Empirical Correlations between Cumulative Absolute Velocity and Amplitude-Based Ground Motion Intensity Measures

Empirical correlation equations are developed between cumulative absolute velocity ( CAV) and other common ground motion intensity measures, namely, peak ground acceleration ( PGA), peak ground velocity ( PGV), 5% damped pseudo spectral acceleration ( SA), acceleration spectrum intensity ( ASI), spectrum intensity ( SI), and displacement spectrum intensity ( DSI). It is found that, for a given earthquake rupture, CAV has the strongest correlation with high and moderate frequency intensity measures (IMs), that is, ASI, PGA, PGV and high-frequency SA, and to a lesser extent with low frequency IMs ( DSI and low-frequency SA). The largest positive correlations of approximately 0.7 however are not high in an absolute sense, a result of the cumulative nature of CAV. The equations allow estimation of the joint distribution of these intensity measures for a given earthquake rupture, enabling the inclusion of CAV, and its benefit as a cumulative intensity measure, in seismic hazard analysis, ground motion selection, and seismic response analysis.

Empirical Correlations between Peak Ground Velocity and Spectrum-Based Intensity Measures

Empirical correlation equations between peak ground velocity ( PGV) and several spectrum-based ground motion intensity measures are developed. The intensity measures examined in particular were: peak ground acceleration ( PGA), 5% damped pseudo-spectral acceleration ( SA), acceleration spectrum intensity ( ASI), and spectrum intensity ( SI). The computed correlations were obtained using ground motions from active shallow crustal earthquakes and four ground motion prediction equations. Results indicate that PGV is strongly correlated (i.e., a correlation coefficient of [Formula: see text]) with SI, moderately correlated with medium to long-period SA (i.e., [Formula: see text] for vibration periods 0.5-3.0 seconds), and also moderately correlated with short period SA, PGA and ASI ([Formula: see text]). A simple example is used to illustrate one possible application of the developed correlation equations for ground motion selection.

Probabilistic Relationships between Ground-Motion Parameters and Modified Mercalli Intensity in California

We use a database of approximately 200,000 modified Mercalli intensity (MMI) observations of California earthquakes collected from USGS “Did You Feel It?” (DYFI) reports, along with a comparable number of peak ground‐motion amplitudes from California seismic networks, to develop probabilistic relationships between MMI and peak ground velocity (PGV), peak ground acceleration (PGA), and 0.3‐s, 1‐s, and 3‐s 5% damped pseudospectral acceleration (PSA). After associating each ground‐motion observation with an MMI computed from all the DYFI responses within 2 km of the observation, we derived a joint probability distribution between MMI and ground motion. We then derived reversible relationships between MMI and each ground‐motion parameter by using a total least squares regression to fit a bilinear function to the median of the stacked probability distributions. Among the relationships, the fit to peak ground velocity has the smallest errors, though linear combinations of PGA and PGV give nominally better results. We also find that magnitude and distance terms reduce the overall residuals and are justifiable on an information theoretic basis. For intensities MMI≥5, our results are in close agreement with the relations of Wald, Quitoriano, Heaton, and Kanamori (1999); for lower intensities, our results fall midway between Wald, Quitoriano, Heaton, and Kanamori (1999) and those of Atkinson and Kaka (2007). The earthquakes in the study ranged in magnitude from 3.0 to 7.3, and the distances ranged from less than a kilometer to about 400 km from the source. Online Material: Figures showing the relationship between 0.3 s, 1.0 s, and 3.0 s pseudospectral acceleration and MMI.

Prediction of Spectral Acceleration Response Ordinates Based on PGA Attenuation

Developed herein is a new peak ground acceleration (PGA)-based predictive model for 5% damped pseudospectral acceleration (SA) ordinates of free-field horizontal component of ground motion from shallow-crustal earthquakes. The predictive model of ground motion spectral shape (i.e., normalized spectrum) is generated as a continuous function of few parameters. The proposed model eliminates the classical exhausted matrix of estimator coefficients, and provides significant ease in its implementation. It is structured on the Next Generation Attenuation (NGA) database with a number of additions from recent Californian events including 2003 San Simeon and 2004 Parkfield earthquakes. A unique feature of the model is its new functional form explicitly integrating PGA as a scaling factor. The spectral shape model is parameterized within an approximation function using moment magnitude, closest distance to the fault (fault distance) and [Formula: see text] (average shear-wave velocity in the upper [Formula: see text]) as independent variables. Mean values of its estimator coefficients were computed by fitting an approximation function to spectral shape of each record using robust nonlinear optimization. Proposed spectral shape model is independent of the PGA attenuation, allowing utilization of various PGA attenuation relations to estimate the response spectrum of earthquake recordings.

An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra

We present a model for estimating horizontal ground motion amplitudes caused by shallow crustal earthquakes occurring in active tectonic environments. The model provides predictive relationships for the orientation-independent average horizontal component of ground motions. Relationships are provided for peak acceleration, peak velocity, and 5-percent damped pseudo-spectral acceleration for spectral periods of 0.01 to 10 seconds. The model represents an update of the relationships developed by Sadigh et. al. (1997) and incorporates improved magnitude and distance scaling forms as well as hanging-wall effects. Site effects are represented by smooth functions of average shear wave velocity of the upper 30 m (VS30) and sediment depth. The new model predicts median ground motion that is similar to Sadigh et. al. (1997) at short spectral period, but lower ground motions at longer periods. The new model produces slightly lower ground motions in the distance range of 10 to 50 km and larger ground motions at larger distances. The aleatory variability in ground motion amplitude was found to depend upon earthquake magnitude and on the degree of nonlinear soil response, For large magnitude earthquakes, the aleatory variability is larger than found by Sadigh et. al. (1997).