We provide ground motion prediction equations for computing medians and standard deviations of average horizontal component intensity measures (IMs) for shallow crustal earthquakes in active tectonic regions. The equations were derived from a global database with M 3.0–7.9 events. We derived equations for the primary M- and distance-dependence of the IMs after fixing the V S30-based nonlinear site term from a parallel NGA-West2 study. We then evaluated additional effects using mixed effects residuals analysis, which revealed no trends with source depth over the M range of interest, indistinct Class 1 and 2 event IMs, and basin depth effects that increase and decrease long-period IMs for depths larger and smaller, respectively, than means from regional V S30-depth relations. Our aleatory variability model captures decreasing between-event variability with M, as well as within-event variability that increases or decreases with M depending on period, increases with distance, and decreases for soft sites.

The NGA-West2 project database expands on its predecessor to include worldwide ground motion data recorded from shallow crustal earthquakes in active tectonic regimes post-2000 and a set of small-to-moderate-magnitude earthquakes in California between 1998 and 2011. The database includes 21,336 (mostly) three-component records from 599 events. The parameter space covered by the database is M 3.0 to M 7.9, closest distance of 0.05 to 1,533 km, and site time-averaged shear-wave velocity in the top 30 m of V S30 = 94 m/s to 2,100 m/s (although data becomes sparse for distances >400 km and V S30 > 1,200 m/s or <150 m/s). The database includes uniformly processed time series and response spectral ordinates for 111 periods ranging from 0.01 s to 20 s at 11 damping ratios. Ground motions and metadata for source, path, and site conditions were subject to quality checks by ground motion prediction equation developers and topical working groups.

The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The research project has been coordinated by the Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. NGA-West2 addresses several key issues in ground-motion seismic hazard, including updating the NGA database for a magnitude range of 3.0–7.9; updating NGA ground-motion prediction equations (GMPEs) for the “average” horizontal component; scaling response spectra for damping values other than 5%; quantifying the effects of directivity and directionality for horizontal ground motion; resolving discrepancies between the NGA and the National Earthquake Hazards Reduction Program (NEHRP) site amplification factors; analysis of epistemic uncertainty for NGA GMPEs; and developing GMPEs for vertical ground motion. This paper presents an overview of the NGA-West2 research program and its subprojects.

A state-of-the-art seismic performance assessment is illustrated through application to a reinforcedconcrete moment-frame building designed per current (2003) building code provisions. Performance is quantified in terms of economic losses and collapse safety. The assessment includes site-specific seismic hazard analyses, nonlinear dynamic structural response simulations to collapse, damage analyses, and loss estimation. When selecting ground motion records for nonlinear dynamic analyses that are consistent with a target hazard level expressed in terms of a response spectral value at the building's fundamental period, it is important to consider the response spectral shape, especially when considering higher hazard levels. This was done through the parameter commonly denoted by . Neglecting these effects during record selection is shown to lead to a factor of 5-10 overestimation of mean annual collapse rate. Structural response simulations, which properly account for uncertainties in ground motions and structural modelling, indicate a 2-7% probability of collapse for buildings subjected to motions scaled to a hazard level equivalent to a 2% probability of exceedance in 50 years. The probabilities of component damage and the means and coefficients of variation of the repair costs are calculated using fragility functions and repair-cost probability distributions. The calculated expected annual losses for various building design variants range from 0.6 to 1.1% of the replacement value, where the smaller losses are for above-code design variants and the larger losses are for buildings designed with minimum-code compliance. Sensitivity studies highlight the impact of key modelling assumptions on the accurate calculation of damage and the associated repair costs.

This paper presents a complete methodology for both probabilistic and deterministic assessment of seismic soil liquefaction triggering potential based on the cone penetration test ͑CPT͒. A comprehensive worldwide set of CPT-based liquefaction field case histories were compiled and back analyzed, and the data then used to develop probabilistic triggering correlations. Issues investigated in this study include improved normalization of CPT resistance measurements for the influence of effective overburden stress, and adjustment to CPT tip resistance for the potential influence of "thin" liquefiable layers. The effects of soil type and soil character ͑i.e., "fines" adjustment͒ for the new correlations are based on a combination of CPT tip and sleeve resistance. To quantify probability for performancebased engineering applications, Bayesian "regression" methods were used, and the uncertainties of all variables comprising both the seismic demand and the liquefaction resistance were estimated and included in the analysis. The resulting correlations were developed using a Bayesian framework and are presented in both probabilistic and deterministic formats. The results are compared to previous probabilistic and deterministic correlations.

We analyze NGA-West2 data and simulations to develop a site amplification model that captures ground motion scaling with V S30 and soil nonlinear effects. We parameterize nonlinearity as the gradient of site amplification with respect to peak acceleration for reference (firm) sites. Both data analyses and simulations indicate nonlinearity for sites with V S30 < 500 m/s and spectral periods T < ∼3 s. Following approximate removal of nonlinear effects from the data, we evaluate V S30-scaling of ground motions, which is most pronounced for T ≥ ∼0.2 s and saturates for hard rock sites. Regional trends in V S30-scaling and nonlinearity were not found to be sufficiently robust to justify inclusion in our model. We apply the site amplification model to derive site factors now approved for building code applications. Principal causes of changes relative to previous values are reduction of the reference velocity (at which amplification is unity) to 760 m/s and reduced nonlinearity.

We develop empirical relationships to predict nonlinear (i.e., amplitudedependant) amplification factors for 5% damped response spectral acceleration as a continuous function of average shear wave velocity in the upper 30 m, V s-30 . We evaluate amplification factors as residuals between spectral accelerations from recordings and modified rock attenuation relationships for active regions. Amplification at low-and mid-periods is shown to increase with decreasing V s-30 and to exhibit nonlinearity that is dependent on V s-30 . The degree of nonlinearity is large for NEHRP Category E (V s-30 Ͻ180 m/s) but decreases rapidly with V s-30 , and is small for V s-30 Ͼϳ300 m/s. The results can be used as V s-30 -based site factors with attenuation relationships. The results also provide an independent check of site factors published in the NEHRP Provisions, and apparent bias in some of the existing NEHRP factors is identified. Moreover, the results provide evidence that data dispersion is dependent on V s-30 .

For engineering systems having a potential for degradation under cyclic loading ͑e.g., landslides, soil profiles subject to liquefaction, some structural systems͒, the characterization of seismic demand should include the amplitude and duration of strong shaking within the system. This article is concerned with significant-duration parameters, which are defined as the time interval across which a specified amount of energy is dissipated ͑as measured by the integral of the square of the ground acceleration or velocity͒. We develop ground-motion prediction equations for significant-duration parameters as a function of magnitude, closest site-source distance, site parameters that reflect shallow geologic conditions as well as deep basin structure, and near-source parameters. The relations are developed using a modern database and a random-effects regression procedure. We find significant duration to increase with magnitude and site-source distance ͑effects that had been identified previously͒, but also to decrease with increasing shear-wave velocity of nearsurface sediments and to increase with increasing basin depth. Parameters that principally measure the duration of body waves were also found to decrease in near-fault areas subject to forward rupture directivity, although such effects were not apparent for other duration parameters that tend to reflect the combined duration of body and surface waves.