Surface wave surveys for seismic site characterization of accelerometric stations in ITACA

Abstract

This paper reports on site characterization for a set of accelerometric stations of the RAN (Italian accelerometric network) with specific attention to the shear wave velocity profile. The latter is indeed of primary importance for the usability of the accelerometric database. Surface wave analysis has been chosen as the primary investigation method since it offers the possibility of reaching the required accuracy with reasonable costs. A range of different techniques, both of the active-source and passive-source types, has been adopted to cope with the objectives of the characterization in relation to specific geological settings. Quality assessment of experimental data has been implemented to check the consistency of the measurements also with respect to the fundamental hypotheses of the method. Strategies to improve the reliability and robustness of the surface wave data inversion were exploited in order to mitigate problems arising from solution non-uniqueness and influence of higher modes in the propagation. Comparisons with independent borehole tests, available at some specific sites, confirm the reliability of the results. Although the research program covered only a subset of the network, the obtained results show the importance of specific experimental investigations aimed at estimating the shear wave velocity profile. Indeed the results lead to a re-classification of several sites with respect to the preliminary classification based on surface geology. Within this context, four selected case histories are reported in the present paper.

Seismic characterization and monitoring of Fucino Basin (Central Italy)

“…The characterization was achieved through the collection of geotechnical data and performing geophysical investigations mainly based on surface waves analysis (Foti et al 2011). In this perspective the analysis of the strongest events recorded by R.A.N.…”

Characterization of site conditions (soil class, VS30, velocity profiles) for 33 stations from the French permanent accelerometric network (RAP) using surface-wave methods

“…Nevertheless, indirect approaches can also often lead to V S30 estimates of high uncertainty. To tackle these issues, important efforts have been made in recent years to perform in situ site characterization of accelerometric stations: e.g., in Italy (Foti et al 2011;Pileggi et al 2011), Switzerland (Michel et al 2014), and the USA (Yong et al 2013).…”

Ground motion prediction equations derived from the Italian strong motion database

“…Besides the enrichment of the database with the recordings relevant to the 2009 L'Aquila seismic sequence, whose mainshock (Mw = 6.3) provided data over a magnitude -distance range scarcely sampled in ITACA, a re-processing of the whole data set has performed within the project S4 (Paolucci et al, 2011), in order to obtain compatible acceleration, velocity and displacement time series. Furthermore, in the framework of the same project, several field surveys were carried out to improve the geophysical characterization of the recording sites (Foti et al, 2011), significantly increasing the number of measured shearwave profiles, used here to classify the sites accordingly to the Eurocode8 (CEN, 2003).…”