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Detailed Reference Information |
Di Giulio, G., Rovelli, A., Cara, F., Azzara, R.M., Marra, F., Basili, R. and Caserta, A. (2003). Long-duration asynchronous ground motions in the Colfiorito plain, central Italy, observed on a two-dimensional dense array. Journal of Geophysical Research 108: doi: 10.1029/2002JB002367. issn: 0148-0227. |
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In winter 1998 a small-aperture (~200 m), four-station array was operating in the middle of the Colfiorito plain. Waveforms of seven small magnitude (2.1 < M < 3.7) local earthquakes are analyzed in this study. The peculiarity of the array seismograms is a ~2-min long duration of the horizontal ground motion. The predominant frequency in the plain is around 1 Hz. In this frequency band, earthquake-induced ground shaking is synchronous for a few seconds during direct S waves; after this time window, wave trains show an increasingly chaotic behavior within the array. The energy variation of the horizontal ground shaking between the array and a nearby rock outcrop exceeds a factor of 500 at 1 Hz. In order to help understanding of observations and construct models for future numerical simulations, the buried structure of the Colfiorito plain has been investigated through seismic refraction profiles and geoelectric measurements. A three-dimensional reconstruction of the basin structure reveals an extremely complex bedrock topography, which is probably a recurrent feature for intermontane basins in tectonically active regions. Apparent velocities and backazimuths in the frequency band 0.5--1.5 Hz indicate that a 180-m deep depression NW of the array is responsible for the generation of edge-diffracted surface (Love) waves. Their arrival to the array breaks the synchronism of vertically reverberating waves which predominate in the first seconds of the S-wave window. |
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Abstract |
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Keywords
Seismology, Body wave propagation, Seismology, Earthquake ground motions and engineering, Seismology, Seismic hazard assessment and prediction, Seismology, Theory and modeling |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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