Joint analysis of Rayleigh-wave dispersion curves and diffuse-field HVSR for site characterization: The case of El Ejido town (SE Spain)

TL;DR

This study combines Rayleigh-wave dispersion and HVSR analysis to characterize El Ejido's deep sedimentary basin, revealing ground properties and seismic response relevant for earthquake risk assessment.

Contribution

It introduces a joint inversion approach using dispersion curves and diffuse-field HVSR to improve site characterization in seismic zones.

Findings

Deep ground features down to Triassic bedrock identified

Ground classified as stiff soil based on models

Predominant periods range from 0.8 to 2.3 seconds

Abstract

The location of El Ejido town over a deep sedimentary basin in a zone of high seismicity in the Spanish context has motivated research on its seismic response characterization. To this aim, S-wave velocity models have been obtained from joint inversion of Rayleigh wave dispersion curves and full-wavefield modelling of the horizontal-to-vertical spectral ratio of ambient noise (HVSR) under the diffuse field assumption (DFA). Combination of spatial autocorrelation surveys (SPAC) with array apertures of several hundred metres and HVSRs displaying low-frequency peaks allowed to characterize deep ground features down to the Triassic bedrock. Predominant periods in the town ranged from 0.8 to 2.3 s, growing towards the SE, with few secondary peaks at higher frequencies. The shallow structure has been explored by means of geotechnical surveys, Multichannel Analysis of Surface Waves (MASW) and SPAC analysis in small-aperture arrays. Resulting models support a general classification of the ground as stiff soil.