Global Ground-motion Prediction Equations Research Articles

Evaluation of the predictive performance of regional and global ground motion predictive equations against Greek strong motion data

The aim of the present work is to evaluate the Ground Motion Prediction Equations (GMPEs), applicable in active shallow crustal regions of Greece, for Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV) and various ordinates of Spectral Acceleration (Sa; 5% damping), to be implemented in Probabilistic Seismic Hazard Analyses (PSHA). The evaluation is data-driven, taking into account the most updated strong-motion dataset for Greece. According to the authors’ knowledge and literature review, such an effort has not been attempted before for Greece, as the selection of GMPEs for PSHA was made based on qualitative criteria. The steps which were followed to fulfill such a goal include: a) pre-selection of regional, pan-European and global GMPEs, suitable for implementation in Greece; b) selection of appropriate data-driven scoring methods; c) scoring of pre-selected GMPEs for both PGA, PGV and four spectral acceleration values Sa; d) final selection of GMPE suite and weighting. The final selection of GMPEs describes adequately the epistemic uncertainty of the strong-motion in Greece and provides a useful tool for addressing a major component of PSHA studies, that is ground motion modelling.

Evaluation of the Predictive Performance of Regional and Global Ground Motion Predictive Equations for Shallow Active Regions in Pakistan

Ground motion prediction equations are a key element of seismic hazard assessments. Pakistan lacks a robust ground motion prediction equation specifically developed using a Pakistan seismic ground motion databank. In this study, performance assessment of the ground motion prediction equations for usage in seismic hazard and risk studies in Pakistan, a seismically highly active region, is performed. In this study, an evaluation of the global ground motion prediction equations developed for the shallow active regions is carried out based on a databank of strong ground motion that was compiled in this study. Thirteen ground motion prediction equations were considered applicable, and their goodness of fit was evaluated using the databank of 147 peak ground acceleration of 27 shallow earthquakes in Pakistan. Residual analysis and three goodness of fit procedures were implemented in the evaluation of the equations. The results of this study suggest that global ground motion prediction equations can be applicable in the shallow active regions of Pakistan. These equations were developed based on data from Europe and the Middle East. Next Generation Attenuation West-2 equations were also applicable, but they did not perform as well as the European and Middle Eastern databank-derived equations. A total of four global equations were applicable in Pakistan. The best performing equation in this study should be applied with the highest weight, and the others should be applied with small weights on the logic tree to perform better. These equations can be employed in seismic hazard and risk assessment studies for disaster risk mitigation measures.

Selection and Modification of Ground Motion Prediction Equations in Different Tectonic Regions of Iran considering Declustered and Non-declustered Earthquake Catalogs

ABSTRACT Shallow crustal earthquakes (SCE) occur in different seismotectonic regions of the Iranian plateau. In this study, 10 ground motion prediction equations (GMPEs) developed based on local, regional, and global data from SCE are considered as candidates to test their explanatory power against Iranian strong motion data. To show the applicability of candidate GMPEs in the plateau as a united region and its different seismotectonic sub-regions, a dataset including 3045 records from 678 seismic events (both mainshocks and aftershocks) is used for statistical analyses. Moreover, using 1662 records from 245 mainshocks, we tried to find more appropriate GMPEs against mainshock ground motions through statistical tests. This work also concentrates on differences in ground motions from mainshock and aftershock earthquakes using the Iranian database. The statistical analyses including LH (Likelihood), LLH (Log-Likelihood) and EDR (Euclidean distance-based ranking) are also performed on GMPEs modified by a local anelastic term. According to the LH and LLH analyses results, local and regional models have better performances for PGA and spectral accelerations (SA) at different periods ranging from 0.05 to 3 sec. However, according to the EDR test, it can be said that some global GMPEs also show acceptable performance for predicting the Iranian ground motions. Also, the adjustment factors added to the GMPEs can considerably improve their explanatory performance.

Ground-motion models for predicting vertical components of PGA, PGV and 5%-damped spectral acceleration (0.01–10 s) in Iran

This paper presents ground motion models to predict vertical components of peak ground acceleration, peak ground velocity, and 5%-damped response spectral acceleration at periods ranging from 0.01 to 10 s. These models are derived from the comprehensive Iranian strong ground-motion database containing 1350 three-component time-histories recorded during 370 earthquakes with 4.5 ≤ $${\text{M}}_{\text{w}}$$ ≤ 7.4. Possible regional dependency of vertical ground-motions to characteristics of three seismo-tectonic regions in Iran was investigated through analysis of variance (ANOVA) technique. Consistent models based on four distance measures; two for point-source ( $${\text{R}}_{\text{epi}}$$ and $${\text{R}}_{\text{hyp}}$$ ) and two for finite-fault ( $${\text{R}}_{\text{JB}}$$ and $${\text{R}}_{\text{rup}}$$ ), were developed. The distribution of inter and intra-event residuals presents satisfactory agreement between actual data and our proposed vertical ground motion prediction equation (GMPE). Furthermore, a detailed comparison between our predictions and four local and global GMPEs is presented, well as horizontal model of Darzi et al. (Bull Seismol Soc Am. https://doi.org/10.1785/0120180196 , 2018). In addition, this study provides period-dependent correlation coefficients between epsilons of different GMPEs corresponds to either horizontal, vertical, or vertical-to-horizontal spectral ratio intensity measures as a function of single or two-periods of interest.

Probabilistic aftershock hazard analysis, two case studies in West and Northwest Iran

Aftershock hazard maps contain the essential information for search and rescue process, and re-occupation after a main-shock. Accordingly, the main purposes of this article are to study the aftershock decay parameters and to estimate the expected high-frequency ground motions (i.e., Peak Ground Acceleration (PGA)) for recent large earthquakes in the Iranian plateau. For this aim, the Ahar-Varzaghan doublet earthquake (August 11, 2012; M N =6.5, M N =6.3), and the Ilam (Murmuri) earthquake (August 18, 2014 ; M N =6.2) have been selected. The earthquake catalogue has been collected based on the Gardner and Knopoff (Bull Seismol Soc Am 64(5), 1363-1367, 1974) temporal and spatial windowing technique. The magnitude of completeness and the seismicity parameters (a, b) and the modified Omori law parameters (P, K, C) have been determined for these two earthquakes in the 14, 30, and 60 days after the mainshocks. Also, the temporal changes of parameters (a, b, P, K, C) have been studied. The aftershock hazard maps for the probability of exceedance (33%) have been computed in the time periods of 14, 30, and 60 days after the Ahar-Varzaghan and Ilam (Murmuri) earthquakes. For calculating the expected PGA of aftershocks, the regional and global ground motion prediction equations have been utilized. Amplification factor based on the site classes has also been implied in the calculation of PGA. These aftershock hazard maps show an agreement between the PGAs of large aftershocks and the forecasted PGAs. Also, the significant role of b parameter in the Ilam (Murmuri) probabilistic aftershock hazard maps has been investigated.

Some Discussions on Data-Driven Testing of Ground-Motion Prediction Equations under the Turkish Ground-Motion Database

ABSTRACTData-driven testing of ground-motion prediction equations (GMPEs) can help researchers in the ranking and selection of GMPEs for seismic hazard assessment. This paper presents and discusses the details of the major features of well-known testing methods which employ likelihood and Euclidean distance concepts. A set of local, regional, and global GMPEs are assessed under a ground-motion database. The data-driven testing of GMPEs is supported by thorough residual analyses under the database, providing valuable insights into the testing of GMPEs. The researchers are advised to evaluate all options together instead of focusing on a specific tool to build well-structured ground-motion logic trees.

Understanding single-station ground motion variability and uncertainty (sigma): lessons learnt from EUROSEISTEST

Accelerometric data from the well-studied valley EUROSEISTEST are used to investigate ground motion uncertainty and variability. We define a simple local ground motion prediction equation (GMPE) and investigate changes in standard deviation (σ) and its components, the between-event variability (τ) and within-event variability (φ). Improving seismological metadata significantly reduces τ (30–50%), which in turn reduces the total σ. Improving site information reduces the systematic site-to-site variability, φS2S (20–30%), in turn reducing φ, and ultimately, σ. Our values of standard deviations are lower than global values from literature, and closer to path-specific than site-specific values. However, our data have insufficient azimuthal coverage for single-path analysis. Certain stations have higher ground-motion variability, possibly due to topography, basin edge or downgoing wave effects. Sensitivity checks show that 3 recordings per event is a sufficient data selection criterion, however, one of the dataset’s advantages is the large number of recordings per station (9–90) that yields good site term estimates. We examine uncertainty components binning our data with magnitude from 0.01 to 2 s; at smaller magnitudes, τ decreases and φSS increases, possibly due to κ and source-site trade-offs Finally, we investigate the alternative approach of computing φSS using existing GMPEs instead of creating an ad hoc local GMPE. This is important where data are insufficient to create one, or when site-specific PSHA is performed. We show that global GMPEs may still capture φSS, provided that: (1) the magnitude scaling errors are accommodated by the event terms; (2) there are no distance scaling errors (use of a regionally applicable model). Site terms (φS2S) computed by different global GMPEs (using different site-proxies) vary significantly, especially for hard-rock sites. This indicates that GMPEs may be poorly constrained where they are sometimes most needed, i.e., for hard rock.

Ground-Motion Prediction Equations based on refined data for dynamic time-history analysis

Ground Motion Prediction Equations (GMPEs) are essential tools in seismic hazard analysis. With the introduction of probabilistic approaches for the estimation of seismic response of structures, also known as, performance based earthquake engineering framework; new tasks are defined for response spectrum such as the reference criterion for effective structure-specific selection of ground motions for nonlinear time history analysis. One of the recent efforts to introduce a high quality databank of ground motions besides the corresponding selection scheme based on the broadband spectral consistency is the development of SIMBAD (Selected Input Motions for displacement-Based Assessment and Design), which is designed to improve the reliability of spectral values at all natural periods by removing noise with modern proposed approaches. In this paper, a new global GMPE is proposed by using selected ground motions from SIMBAD to improve the reliability of computed spectral shape indicators. To determine regression coefficients, 204 pairs of horizontal components from 35 earthquakes with magnitude ranging from Mw 5 to Mw 7.1 and epicentral distances lower than 40 km selected from SIMBAD are used. The proposed equation is compared with similar models both qualitatively and quantitatively. After the verification of model by several goodness-of-fit measures, the epsilon values as the spectral shape indicator are computed and the validity of available prediction equations for correlation of the pairs of epsilon values is examined. General consistency between predictions by new model and others, especially, in short periods is confirmed, while, at longer periods, there are meaningful differences between normalized residuals and correlation coefficients between pairs of them estimated by new model and those are computed by other empirical equations. A simple collapse assessment example indicate possible improvement in the correlation between collapse capacity and spectral shape indicators (<TEX>${\varepsilon}$</TEX>) up to 20% by selection of a more applicable GMPE for calculation of <TEX>${\varepsilon}$</TEX>.

Regional Low‐Magnitude GMPE to Estimate Spectral Accelerations for Earthquake Early Warning Applications in Southern Italy

ABSTRACT A low‐magnitude regional ground‐motion prediction equation (GMPE) for peak ground acceleration and 5% damped spectral acceleration at 11 oscillator periods ranging from 0.1 to 3 s was developed for applications of the earthquake early warning system operating in southern Italy. The accelerometric dataset was built out of 2270 waveforms from 319 earthquakes with local magnitude ranging from 1.5 to 4.2, recorded from 60 stations located on soil type B, according to the Italian Building Code and Eurocode 8, with hypocentral distances ranging from 3 to about 100 km. The GMPE coefficients were computed through a nonlinear weighted damped least‐squares algorithm, attributing a higher weight to ground‐motion data recorded at stations for which soil category was established using geotechnical and geophysical measurements. Predictions of the proposed GMPE were tested against independent ground‐motion data recorded in southern Italy and compared with other regional and global GMPEs through the log‐likelihood method. The comparison shows that the proposed GMPE performs better than any other GMPE considered in this study.

Regional adjustment factors for three NGA-West2 ground-motion prediction equations to be applicable in northern Iran

Ground-motion prediction equations (GMPEs) are essential tools in seismic hazard studies to estimate ground motions generated by potential seismic sources. Global GMPEs which are based on well-compiled global strong-motion databanks, have certain advantages over local GMPEs, including more sophisticated parameters in terms of distance, faulting style, and site classification but cannot guarantee the local/region-specific propagation characteristics of shear wave (e.g., geometric spreading behavior, quality factor) for different seismic regions at larger distances (beyond about 80 km). Here, strong-motion records of northern Iran have been used to estimate the propagation characteristics of shear wave and determine the region-specific adjustment parameters for three of the NGA-West2 GMPEs to be applicable in northern Iran. The dataset consists of 260 three-component records from 28 earthquakes, recorded at 139 stations, with moment magnitudes between 4.9 and 7.4, horizontal distance to the surface projection of the rupture (R JB) less than 200 km, and average shear-wave velocity over the top 30 m of the subsurface (V S30) between 155 and 1500 m/s. The paper also presents the ranking results for three of the NGA-West2 GMPEs against strong motions recorded in northern Iran, before and after adjustment for region-dependent attenuation characteristics. The ranking is based on the likelihood and log-likelihood methods (LH and LLH) proposed by Scherbaum et al. (Bull Seismol Soc Am 94: 2164–2185, 2004, Bull Seismol Soc Am 99, 3234–3247, 2009, respectively), the Nash–Sutcliffe model efficiency coefficient (Nash and Sutcliffe, J Hydrol 10:282–290, 1970), and the EDR method of Kale and Akkar (Bull Seismol Soc Am 103:1069–1084, 2012). The best-fitting models over the whole frequency range are the ASK14 and BSSA14 models. Taking into account that the models’ performances were boosted after applying the adjustment factors, at least moderate regional variation of ground motions is highlighted. The regional adjustment based on the Iranian database reveals an upward trend (indicated as high Q factor) for the selected database. Further investigation to determine adjustment factors based on a much richer database of the Iranian strong-motion records is of utmost important for seismic hazard and risk analysis studies in northern Iran, containing major cities including the capital city of Tehran.

Global Ground Motion Prediction Equation for Shallow Crustal Regions

The Graizer-Kalkan ground-motion prediction equation (GMPE) for peak ground acceleration (PGA) constitutes a series of filters, each of which represents a certain physical phenomenon affecting the radiation of seismic waves from the source. The performance of this GMPE is examined by using about 14,000 records from 245 worldwide shallow crustal events. The recorded data and predictions show an excellent match as far as 100 km from the fault. Beyond 100 km, the data generally show faster attenuation on the order of Rrup−4 due to a relatively low Q (as in the western United States) or slower attenuation on the order of Rrup−1.5 due to a high Q (as in the central and eastern United States). An improved GMPE is developed to account for regional variations in ground motion attenuation. The The new GMPE produces a better match to recorded data up to 500 km from the fault.

Large Apparent Stresses from the Canterbury Earthquakes of 2010 and 2011

An earthquake of Mw 6.1–6.31 (Beavan et al. 2011, page 789 of this issue) that struck Christchurch, New Zealand, on 22 February (21 February, UTC) produced recorded ground motion acceleration over 2 g. The event caused widespread damage with dense recordings of non-linear site behavior. Globally, dense near-field recordings of shallow intraplate earthquakes are rare. It is possible that extreme ground motions are common with this type of earthquake and that their rarity is merely a function of inadequate seismic sampling in the near field of such low-probability, high-potency events. To better define the nature of these events, we calculate apparent stress ( τa ) of the three largest earthquakes in the Canterbury sequence and compare them to global and regional data. We then place recorded PGA and spectral accelerations into the context of regional and global ground motion prediction equations and discuss the implications of high-stress events for future seismic hazard estimates for the region. For the February event, we also briefly explore the implications of directivity on measured ground motions in central Christchurch. The earthquakes that occurred in the Canterbury region of the South Island, New Zealand, from September 2010 to the present have disproportionately large energy magnitudes ( Me ) to their moment magnitudes ( Mw ). They have produced the largest ground motions ever measured in New Zealand. The sequence began with the Mw 7.1 earthquake that occurred about 40 km west of the city of Christchurch on 4 September 2010. The maximum recorded ground acceleration recorded during the event was over 1.25 g, which was experienced near the intersection of the triggering thrust on which the rupture began and the strike-slip Greendale fault that carried most of the moment in the earthquake (Gledhill et al. 2010). Peak ground accelerations (PGA) in the central business district of Christchurch averaged …

A Local Ground-Motion Predictive Model for Turkey, and Its Comparison with Other Regional and Global Ground-Motion Models

We examined the differences between the ground-motion estimations of local and global prediction equations and explored some seismological parameters that may explain these differences. To achieve this objective, we first derived a set of ground-motion prediction equations (GMPEs) for estimating peak horizontal accel- eration, velocity, and pseudospectral acceleration using the recently compiled Turkish ground-motion database. The new GMPEs are comparable with the recent global GMPEs in terms of model sophistication, and they are based on a well-studied national dataset. Using global GMPEs from the Next Generation Attenuation of Ground Motions project (Power et al., 2008) and the pan-European Akkar and Bommer (2010) model, we observed that the discrepancy between local and global GMPEs is more prominent at small magnitudes provided that the GMPEs possess similar mag- nitude limits. Our more detailed comparisons with the pan-European Akkar and Bom- mer (2010) predictive model, as well as with the estimations from a combined Italian and Turkish accelerometric dataset, indicate that depth can be of importance for delineating the differences between local and global GMPEs.

Assessment of Point-Source Stochastic Simulations Using Recently Derived Ground-Motion Prediction Equations

Abstract The simplicity of the point-source stochastic simulation method makes it one of the most appealing tools for the quantification of ground motions for seismic hazard related studies. In this article, we scrutinize the limitations of this technique in terms of fundamental geophysical model parameters. To achieve this objective, we use the estimations of recent Next Generation Attenuation (NGA) and European empirical ground-motion models that are based on global strong-motion databases. The generated synthetics account for the local nonlinear soil effects through 1D site-response analysis. Thus, apart from our major objective, we also derive a probability-based soil-profile model that considers the random variation of shear-wave slowness as a function of depth. We discuss the critical variations of dynamic material properties, such as shear modulus and material damping, during the site-response analysis. We generate a total of 6000 synthetic records with a magnitude range of 5.0≤ M w ≤7.5 and source-to-site distances ( d ) less than 100 km. The site class of the synthetics is defined by the average shear-wave velocity of the upper 30 m soil profile ( V S 30 ), with V S 30 values ranging between 180 m/sec and 1500 m/sec. Our analysis indicates that synthetics that are generated using R hyp (hypocentral distance) as the reference distance metric may fail to describe compatible variations of ground-motion demands with respect to global ground-motion prediction equations (GMPEs), particularly for small-magnitude and short-distance recordings. The performance of synthetics for these latter cases can be improved if one uses R rup (shortest distance from the fault rupture). Our inspections on the frequency-domain behavior of synthetics reveal that they can be reliably used in spectral calculations for periods up to 20 sec. Within the context of this article, we also present a simple baseline correction method to obtain reliable ground displacements from the synthetics that are subjected to site-response analysis.