SEISMIC CHRACTERISTICS OF SURFACE GEOLOGY AND DYNAMIC CHRACTERISTICS OF LOW-RISE BUILDINGS ESTIMATED BY MICROTREMORS TO DISCUSS ON THE BUILDING DAMAGES IN TEHUACAN CITY CAUSED BY THE 1999 EARTHQUAKE.

摘要

This paper is a report on the field surveys on the ground and buildings in Tehuacán City, Mexico, using with refraction test and microtremors observations on the ground, and microitremor only for the buildings. Tehuacán city locates in the epicenter zone of the 1999 Tehuacán Earthquake. After a report of the Tehuacán City office, the affected areas for buildings caused by the earthquake were ubiquitous in the city. These projects had conducted to investigate the relationships between surface geology and damages of buildings caused by the earthquake, and to allow seismic microzonation in the area. From the refraction test, we conclude that the ground surface stratums in Tehuacán City are fairly hard and the layers are very shallow. Observed microtremors show short predominant periods in the observed area in the city, but the forms of spectra are not same. Natural periods of the same types of buildings affected by the 1999 earthquake are very short. Using these results, we can roughly explain the relations between the seismic characteristics of surface geology and the damages of buildings caused by the 1999 earthquake. We can also make a seismic microzonation of the city by this survey results.