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Investigation of Basin Effects in Po Plain in Italy: A Case Study From 2012 Emilia Earthquake Sequence

Description: 

In this case study, we evaluated site amplification observed during the 2012 Emilia earthquake sequence in the Po Plain, Northern Italy. This research not only delves into the amplification characteristics but also assesses the performance of two recently published ground motion models (GMMs) in capturing basin effects in the region. We compiled a comprehensive strong motion flatfile for all of Europe, which includes over 50,000 recordings from at least 6500 earthquakes between 1969 and 2023. Using this flatfile, we extracted approximately 650 strong ground motion records from 99 stations, both inside and along the basin edges of the Po Plain. A significant portion of these records originates from the 2012 Emilia sequence. To estimate single-station ground motion amplification, we utilized three reference rock stations located outside the Po Plain. Our key findings include: 1) significant difference in rock stations response spectra at the north and south edge of Po Plain, due to underlying complex geologic structure; 2) peak amplification generally occurs between spectral periods of 0.7 to 3.0 seconds; and 3) interestingly, the stations along the southern edge exhibited more significant amplification beyond spectral periods of 0.5 seconds relative to northern edge, likely due to basin edge effects. For qualitative isolation of basin edge effect, we performed 1D nonlinear site response analysis using DEEPSOIL at the two stations along southern edge. Results of 1D site response analysis showed peak amplification near the resonance frequency followed by de-amplification, whereas GM records showed sustained amplification. Further, we assessed the performance of two GMMs widely used in the region: the Italian regional model by Lanzano et al. (2019) and the pan-European model by Kotha et al. (2022). The results of robust residual analyses, which utilized all ground motion recording within the Po Plain, indicated that both models tend to underpredict the amplification. However, the regional model demonstrated better performance in capturing part of basin edge amplification compared to the pan-European model.

Session: Why Ignore the Structure? Soil-structure Interaction and Site Response at Local and Regional Scales - I

Type: Oral

Date: 4/17/2025

Presentation Time: 11:30 AM (local time)

Presenting Author: Emel

Student Presenter: No

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