Use of 3-D Ground Motion Simulations in Estimating Future Economic Loss in Mexico City

Abstract eng:
The 1985 Michoacán earthquake highlighted the seismic risk in Mexico City posed by large magnitude (M>7) earthquakes at the subduction interface off the Pacific Coast of Mexico. Although more than 300 km away from the 1985 earthquake, Mexico City suffered a disproportionate amount of overall damage and loss, especially in the lakebed region. Extensive research conducted since the Michoacán earthquake has allowed a better understanding of seismic damage potential in Mexico City. However, many challenges remain in characterizing: a) ground motion attenuation in the region, b) seismic response of soft sediments underneath the city, and c) seismic vulnerability of the ever-changing building stock in the city. In this study, loss estimates for Mexico City were carried out for a selected scenario earthquake at the subduction interface off the Pacific Coast of Mexico. Instead of the conventional method, which uses empirical attenuation relationships combined with site amplification factors, we adopted comprehensive 3-D source-to-site simulations to model the ground motions. These simulations allowed a more thorough consideration of source characteristics and the complexity of seismic wave propagation from the subduction zone through the Trans-Mexican Volcanic Belt and into the Valley of Mexico. The soft sediments underlying Mexico City were represented by a finer mesh in the simulations in order to better capture the basin effects. The simulations provided ground motion time series at the surface, enabling the consideration of duration effects as well as other time and frequency domain characteristics of the resulting ground motions. In order to estimate the impact of the simulated ground motions on the buildings in Mexico City, a database of buildings exposed to the earthquake threat was compiled. Seismic vulnerability of buildings was characterized by analytical modeling of various local building types and by synthesizing damage reports from past local earthquakes. We present preliminary results from ground motion simulations of a selected scenario event and their impact on the current building stock in Mexico City in terms of damage and economic loss.

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