NEHRP Clearinghouse
- Title
- Behavior of Peak Values and Spectral Ordinates of Near-Source Strong Ground Motion Over the Smart 1 Array.
- File
- PB93114833.pdf
- Author(s)
- Niazi, M.
- Source
- National Science Foundation, Washington, DC., June 1990, 129 p.
- Identifying Number(s)
- UCB/EERC-90/17
- Abstract
- The array recordings are used to investigate several important properties of the seismic ground motions themselves. The results reported here address the question of the variability of the peak vertical and horizontal accelerations, velocities and displacements. Statistical treatment of the variability is feasible when ground motions are recorded, as in SMART 1, at a group of stations within a limited distance. The three rings of the SMART 1 array have radii of 200 m, 1 km and 2 km. Since it became operational in September 1980, it has recorded accelerations up to 0.33g and 0.34g on the horizontal and vertical components, respectively. At present there are over 3,000 accelerograms from 53 local earthquakes available. From the set of observations, 12 earthquakes have been selected providing more than 700 accelerograms for analysis and statistical treatment. Nonlinear regression procedure are used to fit the peak values to an attenuation form which has as parameters, earthquake magnitude and source-to-site distance. Spectral information on ground motion is included; correlations are made between spectral ordinate values at 23 discrete frequencies in the range of engineering interest. Among the notable results is the finding that the ratio of the vertical to horizontal response spectral ordinates is less than the often used value of 2/3 for periods longer than about 0.2 second, and also for all frequencies at distances greater than 30 km from the source.
- Keywords
- ; Seismic waves; Seismic arrays; Earth movements; Data acquisition; Spectrum analysis; Earthquake engineering; Regression analysis; Site surveys; Nuclear facilities; Frequencies; Data analysis; Nonlinear systems; Seismic effects; Earthquakes