Tall buildings and flexible structures require a better characterization of long period ground motion spectra than the one provided by current seismic building codes. Motivated by that, a methodology is proposed and tested to improve recorded and synthetic ground motions which are consistent with the observed co-seismic displacement field obtained from interferometric synthetic aperture radar (InSAR) analysis of image data for the Tocopilla 2007 earthquake (Mw=7.7) in Northern Chile. A methodology is proposed to correct the observed motions such that, after double integration, they are coherent with the local value of the residual displacement. Synthetic records are generated by using a stochastic finite-fault model coupled with a long period pulse to capture the long period fling effect. It is observed that the proposed co-seismic correction yields records with more accurate long-period spectral components as compared with regular correction schemes such as acausal filtering. These signals provide an estimate for the velocity and displacement spectra, which are essential for tall-building design. Furthermore, hints are provided as to the shape of long-period spectra for seismic zones prone to large co-seismic displacements such as the Nazca-South American zone.
Bibliographical noteFunding Information:
This work was supported by CONICYT/PBCT Proyecto Anillo de Investigación en Ciencia y Tecnología ADI#30/2006 (Chile), the authors wish to acknowledge the commission. This research was also partially funded by Fondecyt project 1085282. The authors are very grateful of the support of Dr. Matthew Pritchard, who provided us with the inversion results and insight for the Antofagasta (1995) earthquake; of Dr. Gail Atkinson and Dr. Dariush Motazedian, authors of the stochastic simulation software EXSIM used herein; and Dr. Sergio Ruiz who provided us with the Tocopilla records and the instrument information to correct them. Raw SAR scenes from ESA Category-1 contract 5266 and the WINSAR consortium.