The M_w 9.0 Tohoku-oki Japan earthquake and many of its subsequent aftershocks and triggered events were very well recorded, providing opportunity for detailed study of source, path, and site effects. In previous work, we utilized mainshock data to demonstrate faster attenuation with distance in backarc than in forearc regions, positive event terms for high frequency intensity measures for multiple ground motion prediction models, and minimal scaling of site amplification with V_s30 at high frequencies. In this paper, we consider two subsequent events, one M_w 6.7 on the plate interface that ruptured in the mainshock and one M_w 6.3 inland from the volcanic front, to examine if similar ground motion features are apparent from these data sets. We continue to find evidence for the divergence in attenuation rate in forearc and backarc regions, despite the fact that the events are located on opposite sides of the volcanic front. The site response for these events does not appear to follow previously observed patterns for Japan, being relatively similar to V_s30-scaling in active crustal regions generally. 

Ground-motion prediction equations (GMPEs) relate a ground-motion parameter (e.g. peak ground acceleration) to a set of explanatory variables describing the source, wave propagation path and site conditions. In the past five decades many hundreds of GMPEs for the prediction of PGA and linear elastic response spectral ordinates have been published. An accompanying paper discusses the pre-selection of GMPEs undertaken within the framework of the Global Earthquake Model (GEM) Global GMPEs project, coordinated by the Pacific Earthquake Engineering Research Center (PEER). Here, we discuss the following step undertaken to reduce the long list of pre-selected models down to a more manageable number for global hazard assessments. The procedure followed, consisting of an examination of themulti-dimensional (e.g. magnitude, distance and structural period) predicted ground-motion space in various ways and published quantitative tests of the GMPEs against observational data not used for their derivation, is discussed and illustrated for subduction zones.

We review site parameters used in ground motion prediction equations (GMPEs) for various tectonic regimes and describe procedures for estimation of site parameters in the absence of site-specific data. Most modern GMPEs take as the principal site parameter the average shear wave velocity in the upper 30 m of the site (V_s30) either directly or as the basis for site classification into categories. Three GMPEs developed for active regions also use basin depth parameters. We review estimation procedures for V_s30 that utilize surface geology, terrain-based site categories, ground slope, or combinations of these. We analyze the relative efficacy of those procedures using a profile data set from California assembled in a recent NGA project. The results indicate that no single procedure is most effective and that prediction dispersion is lower for young sediments than for stiff soils or rock.

The time-averaged shear wave velocity in the upper 30 m of a site (V_s30) is the most common site parameter used in ground motion prediction equations for the evaluation of seismic site response. It is often the case that V_s30 is not available at sites with earthquake recordings; for example in the NGA-East site database only 45 of 1149 sites have measured values of V_s30. Accordingly, estimates of V_s30 are often made on the basis of available proxies that are widely available such as ground slope, geomorphic terrain categories, and surface geology. We compile a database of 1930 measured and inferred V_s30 values in Central and Eastern North America (CENA) to test slope and geomorphology-based proxy methods. The results indicate that these existing proxy methods are biased for sites with V_s30greater than 400 m/s. Based on a careful review of geological conditions in the CENA, we propose nineteen geologic classes based on setting (i.e., glaciated or non-glaciated), age, and depositional environmental that can form the basis for geology-based proxy estimates of V_s30 as well as for simplified stratigraphic columns.