SITE EFFECT AND DAMAGE DISTRIBUTION IN PUJILI (ECUADOR) AFTER THE 28 MARCH 1996 EARTHQUAKE

The 28 March 1996 earthquake (Mw = 5.7) produced extensive damage in P ujili, a small town located in the central part of the Inter-Andean va lley of Ecuador. Variations in the damage rate of adobe constructions throughout the city let us suppose a ground motion amplification relat ed to site effects. A site effect study using the HIV spectral ratio c onfirmed the good agreement with geological formations and showed that a second peak in some soil response appears at sites that are located over a zone of alluvial deposits, in the most damaged area of the cit y. This second peak is in the frequency range 5-7 Hz, close to the nat ural response of adobe building frequency. Thus, the second peak seems to increase the damage rate of adobe buildings and may be related to superficial alluvial deposits of a river, acting independently of the rest of the soil column. (C) 1998 Elsevier Science Ltd. All rights res erved.