Comparisons of the NGA Ground-Motion Relations

Abstract

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km. Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation.

The role of topography and lateral velocity heterogeneities on near-source scattering and ground-motion variability

“…Abrahamson et al 2008). This further confirms the importance of modelling complex wave propagation phenomena such as scattering in the near source region even at intermediate frequency.…”

“…By comparison, standard deviation from empirical ground-motion prediction equations at 30 km on rock soils (Abrahamson et al 2008). It is therefore important to consider the combined effect on ground-motion variability of both topography and velocity heterogeneity.…”

Bayesian network modeling of correlated random variables drawn from a Gaussian random field

“…Finally, the layout in which points are arranged in clusters is considered. Figure 12 shows examples of 9-site layouts arranged into three three-site clusters centered at coordinates (0,0), (50,50) and (25,75). For each cluster, points are equally distributed around a circle of radius .…”

“…Readers familiar with seismic applications will recognize (17) as the general formulation of a ground-motion prediction equation (also known as an attenuation relation), see, e.g. [25].…”

Investigating Possible Regional Dependence in Strong Ground Motions

“…The recent set of NGA GMPEs (e.g. Abrahamson et al, 2008) do use some data from EMME but the models are not highly dependent on these data. Stafford et al (2008) quantitatively examine, using an extended Scherbaum et al (2004) technique, the ability of one of the NGA models to predict observed ground motions in EMME.…”