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 Sismologico Nacional (Mexico). This station started operations in January 2006 in the Facultad de Ciencias de Ia Tierra from the Universidad Autonoma de Nuevo Leon, in Linares, Nuevo Leon, 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, V530, and (b) the resonance frequency. We got V530 = 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 eta/. (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.