Comment on "Estimation of Ground Motion in Mexico City from a Repeat of the M 7.0 Acambay Earthquake of 1912" by S. K. Singh, A. Iglesias, M. Ordaz, X. Perez-Campos, and L. Quintanar

Abstract

Singh et al. (2011) estimate the ground motion in Mexico City in case of a recurrence of the M ∼7.0 Acambay crustal earthquake of 1912, an event that ruptured to the surface along several normal faults of a major intra‐arc lake basin within the Trans‐Mexican volcanic belt, ∼100 km northwest of the capital. From their assessment, they conclude that a repeat of the event would not present a significant hazard to Mexico City, a conclusion they find confirmed in their assumption that the Acambay earthquake was felt there with a modified Mercalli intensity (MMI) of IV. In this comment, I show that Singh et al. (2011) severely underestimate the macroseismic intensity of this event in the historical part of Mexico City, which was more likely an MMI of VII–VIII. Consequently, their ground‐motion estimates are unrealistically low. Based on the observed macroseismic intensity of the 1912 earthquake, the linear seismic sources of the Acambay graben fault network, up to 80 km long, pose a significant hazard to the Mexico City region, especially to its northwestern suburbs located on lake deposits, such as Tlalnepantla and the Cuautitlan area. The assumption by Singh et al. (2011) that the 1912 Acambay earthquake was felt in Mexico City with an MMI of IV is based on the work by Urbina and Camacho (1913), who indicate felt intensities in the range of III–IV on the twelve‐degree 1904 Cancani scale (Musson et al. , 2010) for five locations in the southern part of the Mexico City basin. However, Urbina and Camacho (1913) do not provide macroseismic intensity observations for the colonial center of Mexico City. Singh et al. (2011) wrongly assume that the 1912 Acambay earthquake did not cause damage in Mexico City. One day after the mainshock, El Imparcial , the leading Mexican national newspaper of its time, provided a detailed description …