Seismic microzoning from synthetic ground motion parameters: Case study, Santiago de Cuba

Synthetic seismograms (P - SV and SH waves) have been calculated along 6 profiles in Santiago de Cuba basin, with a cutoff frequency of 5 Hz, by using the hybrid approach (modal summation for a regional (ID) structure plus finite differences for a local (2D) structure embedded in the first). They correspond to a scenario earthquake of M sub S = 7 that may occur in Oriente fault zone, directly south of the city. As initial data for a seismic microzoning, the characterisation of earthquake effects has been made considering several relative (2D/1D) quantities (PGDR, PGVR, PGAR, DGAR, I sub A R etc.) and functions representative of the ground motion behaviour in soil (2D) with respect to bedrock (ID). The functions are the response spectra ratio RSR(f), already routinely used in this kind of work, and the elastic energy input ratio E sub I R(f), defined, for the first time, in this paper. These data, sampled at 105 sites within all the profiles have been classified in two steps, using logical combinatory algorithms: connected sets and compact sets. In the first step, from the original ground motion parameters or functions extracted from the synthetic seismograms, 9 sets have been classified and the partial results show the spatial distribution of the soil behaviour as function of the component of motion. In the second step, the results of the classification of the 9 sets have been used as input for a further classification that shows a spatial distribution of sites with a quasi-homogeneous integral ground motion behaviour. By adding the available geological surface data, a microzoning scheme of Santiago de Cuba basin has been obtained.