Journal of Natural Disaster Science

MEASUREMENTS OF MICROTREMORS IN BUILDINGS IN MEXICO CITY AFTER THE SEPTEMBER 19, 1985 MICHOACAN EARTHQUAKE

Tadao MINAMI
Earthquake Research Institute, University of Tokyo
and
Toshihide KASHIMA
Building Research Institute, Ministry of Construction

(Received 4 April, 1990 and in revised form 17 September, 1990)

Abstract

We had the opportunity to measure the microtremors of 46 buildings in Mexico City as members of the Technical Cooperation Mission that the Japan International Cooperation Agency (JICA) dispatched to work in Mexico from 19 October to 22 November 1985. Fourier analyses of the recorded microtremor data provided useful information about the dynamic properties of buildings damaged or undamaged by the 1985 Michoacan earthquake. The measured natural periods suggested that the rigidity of the undamaged buildings in Mexico City is only 1/2 to 1/3 that of Japanese buildings. Moreover, there was an apparent difference in the natural periods of the damaged and undamaged buildings.

Key words

microtremors, Michoacan earthquake, damping coefficient, damaged buildings