Ground accelerations and empirical site classification through H/V response spectral ratio (HVRSR) using historical records from the strong motion network of the Aburrá Valley, Colombia

• Published in: Soil dynamics and earthquake engineering (1984) 2022-01, Vol.152, p.107063, Article 107063
• Main Authors: Posada, Gustavo, Monsalve, Gaspar, Hoyos, Carlos D., Pérez-Hincapié, Ana M., Trujillo-Cadavid, Juan Camilo
• Format: Article
• Language: English
• Subjects: Alluvial deposits; Amplification; Chemical weathering; Classification; Earthquakes; Geology; Metropolitan areas; Municipalities; Period ground motion; PGA; Response spectra; Response spectrum; Rigidity; Seismic activity; Seismic response; Seismic waves; Soft soils; Soil classification; Valleys
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2021.107063

Using data from the strong motion network of the Aburrá Valley in Colombia, consisting of approximately 24 years of records, we studied the seismic response of 30 sites in the Metropolitan area of the city of Medellín and surrounding municipalities. The network recorded over 240 earthquakes since 1996, with magnitudes between 1.7 and 6.7. The strong motion records indicate a maximum Peak Ground Acceleration (PGA) of 0.05 g (55 gals). We computed the damped 5% response spectra to estimate the soil's natural periods at each site, using the Horizontal-to-Vertical Response Spectral Ratio (HVRSR). The fundamental periods vary from ∼0.1 s to ∼0.5 s, allowing us to perform a first-order characterization of soil rigidity as well as the classification of the soils in five categories. This classification shows a reasonable relationship with the local geology in the Aburrá Valley, which mainly consists of a metamorphic basement, igneous intrusions, and slope and alluvial deposits, with a highly variable degree of mechanical and chemical weathering. The relatively short fundamental periods indicate an absence of soft soils among the station sites, often associated with the largest amplification of seismic waves. The classes identified show spectral amplifications on natural periods, relative to hard-rock, with factors between 2 and 4.5. •Peak Ground Acceleration recorded in the Aburrá Valley in northwestern Colombia, using a Strong Motion Network•Site natural periods were inferred from the H/V spectral ratio.•Site classification is consistent with local geology.