Seismic characterization of station LNIG as a reference site in Northeast Mexico

Abstract

Station LNIG is part of the new generation of seismological observatories that have been recently installed in Mexico by the Servicio Sismológico Nacional (Mexico). This station started operations in January 2006 in the Facultad de Ciencias de la Tierra from the Universidad Autónoma de Nuevo León, in Linares, Nuevo León, Mexico. We evaluate the site response at LNIG according to the definition of standard reference rock site. We obtained (a) the average shear wave velocity for the first 30 m depth, VS30, and (b) the resonance frequency. We got VS30 = 1870 m/s from seismic refraction profiles. This corresponds to a hard rock site type A in accordance to NEHRP. On the other hand, the spectral ratios were obtained from microtremors and local weak-motion earthquakes (3.1 ≤ M ≤ 4.5), they show a flat response (unitary amplitude) for the frequency range from 0.2 to 20 Hz. According to the definition proposed by Steidl et al. (1996) and Cadet et al. (2010), the LNIG site, located on shale of the Mendez Formation of the Upper Cretaceous, corresponds to a reference site.