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Estimating Cross-Coupling in Site Response by Seismic Noise Interferometry: An Example From an Alpine Valley (Northeastern Italy)

Description: 

The assessment of site response is an important task for improved seismic hazard estimation. However, standard approaches for site response estimation generally neglect the cross-coupling effect among the three components of motion due to heterogeneities in the subsurface structure. The existing methods for estimating the 3D frequency response require the selection of data according to some restrictive criteria and they are difficult to be applied in areas of moderate seismicity. Moreover, they are based on the analysis of earthquake recordings and, therefore, the possibility of their application in large urban areas is hampered by the limitation of available recordings (mainly from ad-hoc installed temporary networks), and the strong seismic noise that can limit the detection capability.

We propose a method for estimating cross-coupling effects by the inversion of the deconvolved wavefield derived from seismic noise analysis in which the 3-components of the ground motion recorded at one site are deconvolved with those recorded at a reference site. The procedure provides the 9-components of the frequency response function (and of the corresponding deconvolved wavefield) and allows the identification of possible cross-coupling effects. The procedure is applied to a set of recordings collected in the Sarca Valley (northeastern Italy) by a temporary seismometric network. The results show that at the studied site the components of cross-coupling are not-negligible and are related to the lateral variations of bedrock surface and the heterogeneities within the sedimentary cover. The application of semblance analysis allows the nature of the wavefield within the valley to be characterized. The results can be used to better constrain the subsurface model and thus improve the reliability of the synthetic seismograms.

Session: From Sensors and Networks to Site Characterization and Site Response: Coming Full Circle

Type: Oral

Date: 4/18/2023

Presentation Time: 02:00 PM (local time)

Presenting Author: Stefano Parolai

Student Presenter: No

Invited Presentation: 

Authors