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http://hdl.handle.net/2122/15766
Authors: | Sgattoni, Giulia* Castellaro, Silvia* |
Title: | Detecting 1-D and 2-D ground resonances with a single-station approach | Journal: | Geophysical Journal International | Series/Report no.: | /223 (2020) | Publisher: | Oxford University Press - The Royal Astronomical Society | Issue Date: | 2020 | DOI: | 10.1093/gji/ggaa325 | Abstract: | The vibration modes of the ground have been described both in the 1-D and 2-D case. The 1-D resonance is found on geological structures whose aspect ratio is low, that is on layers with a lateral width much larger than their thickness. A typical example is that of a horizontal soft sediment layer overlying hard bedrock. In this case, the 1-D resonance frequency, traditionally detected by means of the microtremor H/V (horizontal to vertical spectral ratio) technique, depends on the bedrock depth and on the shear wave velocity of the resonating cover layer. The H/V technique is thus used both to map the resonance frequencies in seismic microzonation studies and for stratigraphic imaging. When 2-D resonance occurs, generally on deep and narrow valleys, the whole sedimentary infill vibrates at the same frequency and stratigraphic imaging can no longer be performed by means of the 1-D resonance equation. Understanding the 1-D or 2-D resonance nature of a site is therefore mandatory to avoid wrong stratigraphic and dynamic interpretations, which is in turn extremely relevant for seismic site response assessment. In this paper, we suggest a procedure to address this issue using single-station approaches, which are much more common compared to the multistation synchronized approach presented by research teams in earlier descriptions of the 2-D resonances. We apply the procedure to the Bolzano sedimentary basin in Northern Italy, which lies at the junction of three valleys, for which we observed respectively 1-D-only, 1-D and 2-D, and 2-D-only resonances. We conclude by proposing a workflow scheme to conduct experimental measurements and data analysis in order to assess the 1-D or 2-D resonance nature of a site using a single-station approach. | Description: | This article has been accepted for publication in Geophysical Journal International ©: The Authors 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy. |
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