Site characterization in the Vega Baja, SE Spain, using ambient-noise H/V analysis

Abstract

New available geological, geotechnical, and geophysical data and new acquired ambient-noise surveys allowed for a detailed characterization of the soils in the Vega Baja region, located in the Lower Segura River basin, SE of the Iberian Peninsula. Single-station measurements were carried out at 90 sites, mainly over the central area of the basin, checking reproducibility by repeating some measurements under different conditions, on different dates, and through different acquisition systems, following well established standard procedures. The detailed data processing and analysis of the new acquired ambient-noise records provided the identification of multiple peaks in some of the horizontal-to-vertical spectral ratio curves, representing different impedance contrasts at depth that were 1D modelled to characterize the Vega Baja soils in terms of resonant frequencies, average shear-wave velocity, thickness of the different soil units, depth to the engineering bedrock and depth to the rock units when the model includes it. The depth to the engineering bedrock is around 30 m in the central part of the region, reaching maximum values of about 50 m in the north and to the east. Maximum values of the shear-wave velocity averaged over the soil units are close to 200 m/s while that averaged in the top 30 m reach values around 300 m/s south of the river bank. Contour mapping and cross-sections of the obtained model parameters illustrate the soil characteristics over the region, providing relevant information for the generation of representative sets of seismic hazard scenarios at different probability levels in future studies for their application in risk mitigation and emergency planning in the Vega Baja.

A proxy-based model for estimating V30 in the Iberian Peninsula

“…This category compiles measurements used in works described in papers published in journals and/or conference proceedings and not belonging to the previous category. A total of 322 sites coming from eight publications have been included (García-Fernández & Jiménez, 2012;Carvalho et al, 2013;Alguacil et al, 2014;Dias et al, 2014;Navarro et al, 2014a,b;Rueda et al, 2015;Vilanova et al, 2018;). From the work by Vilanova et al (2018), only the measurements not already included in the publications of Carvalho et al (2013) and Dias et al (2014) were added to avoid duplication.…”

Horizontal seismic wave at ground surface from transfer function based on ambient noise

“…At this time, an ambient noise signal is utilized because it includes a resonance effect on the media. Many studies have already analyzed the correlation with the predominant and/or fundamental frequency of the site characterization from ambient noise (Albarello and Lunedei, 2010;García-Fernández and Jiménez, 2012;Cultrera et al, 2014;Moisidi et al, 2015;Asten and Hayashi, 2018). The aim of this study was to determine a transfer function to convert motion recorded at a borehole to that occurring at the ground surface, without the need for site-specific response analysis.…”

Avances metodológicos en la evaluación de la vulnerabiblidad sísmica en la trama urbana

“…32 2.-EVALUACIÓN DEL RIESGO SÍSMICO EN ÁREAS URBANAS. ESTADO DEL ARTE Macau, 2008;González ,2010), diversas ciudades en Andalucía (Cheddadi, 2001;Navarro et al, 2007;Goded, 2010;Schmidt, 2010;Gaspar-Escribano et al, 2010b), o el Sureste peninsular (Ribó, 2010;Rosa-Cintas et al, 2011;García-Fernández & Jiménez, 2012 En lo relativo a la ciudad de Lorca, aunque previamente al terremoto de 2011 se habían publicado ya algunos estudios de microzonación (Navarro et al 2006(Navarro et al , 2008, tras el sismo estos se han intensificado notablemente (Figueras et al, 2012;Pérez-Cuevas et al, 2013;Alguacil et al, 2014;Navarro et al, 2014;Martínez-Pagán et al, 2014) La vulnerabilidad sísmica es la segunda variable interviniente en el proceso de evaluación del riesgo sísmico (Figura 1.5). Se puede definir como la predisposición intrínseca a sufrir daño de una cierta estructura ante la ocurrencia de un movimiento sísmico de una determinada severidad (Barbat et al, 2010).…”