The September 7, 2017 Tehuantepec, Mexico, earthquake: Damage assessment in masonry structures for housing

Abstract

Mexico is located among five tectonic plates. Therefore, it is frequently disturbed by the action of several moderate and strong earthquakes, affecting both the population and its infrastructure. The origin, causes, and effects of the typical observed damage patterns during the September 7, 2017 Tehuantepec earthquake (Mw = 8.2), in masonry houses and apartment buildings, located in cities and towns of the Mexican states of Chiapas and Oaxaca in a radius of about 250 km from the epicenter are reported and discussed in this paper. The high structural vulnerability and the severity of the earthquake resulted in the death of 96 people and more than 110,000 houses damaged, where more than 41,000 were considered total losses (collapse, beyond repair or tagged for demolition). In order to analytically evaluate the seismic vulnerability of typical masonry structures ranging from one to five stories, displacement ductility demand spectra (DDDS) were computed for both earthquake ground motions records and artificial acceleration records for a wide range of base shear capacities. Special attention is given to relate the observed damage with conditions of structural irregularity. Effects of flexible diaphragms, structural pounding between adjacent structures and site effects are also addressed. From the information presented, it can be concluded that most of the observed typical damage it is mostly due to poor design, inadequate construction processes, poor quality of construction materials and low wall density ratios. Finally, it was clearly observed that DDDS is a useful tool for the simplified seismic vulnerability assessment of a large portfolio of existing structures under a given earthquake scenario.