Showing papers by "David M. Boore published in 2012"

Predominant-period site classification for response spectra prediction equations in Italy

Abstract: We propose a site-classification scheme based on the predominant period of the site, as determined from the average horizontal-to-vertical (H/V) spectral ratios of ground motion. Our scheme extends Zhao et al. (2006) classifications by adding two classes, the most important of which is defined by flat H/V ratios with amplitudes less than 2. The proposed classification is investigated by using 5%-damped response spectra from Italian earthquake records. We select a dataset of 602 three-component analog and digital recordings from 120 earthquakes recorded at 214 seismic stations within a hypocentral distance of 200 km. Selected events are in the moment- magnitude range 4:0 ≤ Mw ≤ 6:8 and focal depths from a few kilometers to 46 km. We computed H/V ratios for these data and used them to classify each site into one of six classes. We then investigate the impact of this classification scheme on empirical ground-motion prediction equations (GMPEs) by comparing its performance with that of the conventional rock/soil classification. Although the adopted approach results in only a small reduction of the overall standard deviation, the use of H/V spectral ratios in site classification does capture the signature of sites with flat frequency-response, as well as deep and shallow-soil profiles, characterized by long- and short-period reso- nance, respectively; in addition, the classification scheme is relatively quick and inexpensive, which is an advantage over schemes based on measurements of shear- wave velocity. Online Material: Tablesofparametersdefiningthegroundmotion predictionequa- tions, and figures of H/V spectral ratios, intraevent residuals, and spectral amplitudes.

Using Pad‐Stripped Acausally Filtered Strong‐Motion Data

Abstract: Most strong-motion data processing involves acausal low-cut filtering, which requires the addition of sometimes lengthy zero pads to the data. These padded sections are commonly removed by organizations supplying data, but this can lead to incompatibilities in measures of ground motion derived in the usual way from the padded and the pad-stripped data. One way around this is to use the correct initial conditions in the pad-stripped time series when computing displacements, velocities, and linear oscillator response. Another way of ensuring compatibility is to use post- processing of the pad-stripped acceleration time series. Using 4071 horizontal and vertical acceleration time series from the Turkish strong-motion database, we show that the procedures used by two organizations—ITACA (ITalian ACcelerometric Archive) and PEER NGA (Pacific Earthquake Engineering Research Center-Next Generation Attenuation)—lead to little bias and distortion of derived seismic-intensity measures.

Empirical Improvements for Estimating Earthquake Response Spectra with Random‐Vibration Theory

Abstract: The stochastic method of ground-motion simulation is often used in combination with the random-vibration theory to directly compute ground-motion in- tensity measures, thereby bypassing the more computationally intensive time-domain simulations. Key to the application of random-vibration theory to simulate response spectra is determining the duration (Drms) used in computing the root-mean-square oscillator response. Boore and Joyner (1984) originally proposed an equation for Drms, which was improved upon by Liu and Pezeshk (1999). Though these equations are both substantial improvements over using the duration of the ground-motion ex- citation for Drms, we document systematic differences between the ground-motion intensity measures derived from the random-vibration and time-domain methods for both of these Drms equations. These differences are generally less than 10% for most magnitudes, distances, and periods of engineering interest. Given the systematic nature of the differences, however, we feel that improved equations are warranted. We empirically derive new equations from time-domain simulations for eastern and western North America seismological models. The new equations improve the random-vibration simulations over a wide range of magnitudes, distances, and oscil- lator periods. Online Material: SMSIM parameter files, tables of coefficients and model parameters, and shaded contour plots of TD/RV ratios for two WNA models.

Compilation and critical review of GMPEs for the GEM-PEER Global GMPEs Project

Abstract: SUMMARY: Ground-motion prediction equations (GMPEs) relate a ground-motion parameter (e.g. peak ground acceleration, PGA) 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. We discuss the pre-selection of GMPEs undertaken within the framework of the GEM-PEER Global GMPEs Project. The pre-selection criteria adopted were consistent with the current state-ofthe-art in ground-motion characterization and sought to retain only the most robust GMPEs. Consideration of broad tectonic regionalization (e.g. shallow crustal seismicity in tectonically-active areas, stable continental regions and subduction zones) was made but it was assumed (based on previous studies) that strong regional differences were not present within these tectonic classes. In total about thirty GMPEs were pre-selected for closer inspection and testing to obtain a final set of ground-motion models.

Updated Determination of Stress Parameters for Nine Well-Recorded Earthquakes in Eastern North America

Abstract: Stress parameters (Δ σ ) are determined for nine relatively well-recorded earthquakes in eastern North America for ten attenuation models. This is an update of a previous study by Boore et al. (2010). New to this paper are observations from the 2010 Val des Bois earthquake, additional observations for the 1988 Saguenay and 2005 Riviere du Loup earthquakes, and consideration of six attenuation models in addition to the four used in the previous study. As in that study, it is clear that Δ σ depends strongly on the rate of geometrical spreading (as well as other model parameters). The observations necessary to determine conclusively which attenuation model best fits the data are still lacking. At this time, a simple 1/ R model seems to give as good an overall fit to the data as more complex models.

Site effects in parametric ground motion models for the GEM-PEER Global GMPEs Project

Abstract: 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 (Vs30) 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 Vs30 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.

Updated Determination of Stress Parameters for Nine Well-Recorded Earthquakes in Eastern

Abstract: Stress parameters (∆ σ) are determined for nine relatively wellrecorded earthquakes in eastern North America for ten attenu

Selection of a Global Set of GMPEs for the GEM-PEER Global GMPEs Project

Abstract: 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.