NGA Project Strong-Motion Database

Abstract

A key component of the NGA research project was the development of a strong-motion database with improved quality and content that could be used for ground-motion research as well as for engineering practice. Development of the NGA database was executed through the Lifelines program of the PEER Center with contributions from several research organizations and many individuals in the engineering and seismological communities. Currently, the data set consists of 3551 publicly available multi-component records from 173 shallow crustal earthquakes, ranging in magnitude from 4.2 to 7.9. Each acceleration time series has been corrected and filtered, and pseudo absolute spectral acceleration at multiple damping levels has been computed for each of the 3 components of the acceleration time series. The lowest limit of usable spectral frequency was determined based on the type of filter and the filter corner frequency. For NGA model development, the two horizontal acceleration components were further rotated to form the orientation-independent measure of horizontal ground motion (GMRotI50). In addition to the ground-motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record was also developed. NGA data have been systematically checked and reviewed by experts and NGA developers.

An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

“…used to compute the spectra [Boore et al, 2012;Chiou et al, 2008]. The response spectra were also computed for each horizontal component of the records following the Nigam and Jennings [1969] method with a damping of 5%.…”

Assessment of concrete bridges subjected to ground motion with an arbitrary angle of incidence: static and dynamic approach

“…The two prevailing modes define the modal principal axes of Pedini bridge ( Figure 6, system O-M1-M2) and they become identical with the geometric principal axes ( Figure 6, system Oxy), something that is caused by the straight in plan geometry of the selected bridge. At first, the dynamic response of the selected bridge for different angles of incidence of the bidirectional excitation is investigated in comparison to the simpler case of unidirectional excitation for seven ground motions (Table 2), which have been selected according to the following procedure: At first, 30 ground motions with magnitude, M, from 5.8 to 6.8 and epicentral distance, R, from 15km to 40km were selected; 5 of them are records from greek earthquakes and they were extracted from the European Strong Motion Database (Ambraseys et al 2000), while the rest 25 are records from all over the world and they were extracted from the PEER-NGA database (Chiou et al 2008) using the ISSARS software (Katsanos et al 2011). Apart from the (M, R) criterion, the similarity of the response spectra of the records and those of the spectrum used for the design of the bridge (A g = 0.16g, Soil C) was also considered in the selection, while an effort was also made to select records from different earthquakes, to avoid bias in the results.…”

High-frequency filtering of strong-motion records

“…When processing strong-motion data for the Next Generation Attenuation (NGA) database the cut-off frequencies of both low-and high-cut filters were selected by visual inspection of each time series and associated FAS (Darragh et al, 2004;Chiou et al, 2008). This is unusual, as the individual selection of high-cut filters has not generally been standard practice in processing strong-motion data, for even if care is taken in the choice of low-cut filters, uniform high-cut filters are often employed (e.g.…”