Preprints
https://doi.org/10.5194/nhess-2023-233
https://doi.org/10.5194/nhess-2023-233
26 Jan 2024
 | 26 Jan 2024
Status: a revised version of this preprint is currently under review for the journal NHESS.

The quest for reference stations at the National Observatory of Athens, Greece

Olga-Joan Ktenidou, Antonia Papageorgiou, Erion-Vasilis Pikoulis, Spyros Liakopoulos, Fevronia Gkika, Ziya Cekinmez, Panagiotis Savvaidis, Kalliopi Fragouli, and Christos P. Evangelidis

Abstract. The assumption of reference station conditions is investigated for the first time across 60 rock stations belonging to the broadband and accelerometric networks of the National Observatory of Athens. We select the stations based on the established belief that they lie on rock, and provided their data are publicly available through EIDA/NOA and have been for long enough to yield a substantial number of recordings. No site effects studies have been conducted before for the ensemble of the stations under study. Furthermore, no ad hoc field campaigns have been performed to characterise them, save in 2 cases. The first step is to compile all existing information for these stations from all publicly available sources and past studies, including geology, topography, station installation, Vs30 estimates and any other known metadata. The second step is to compile ad-hoc information from maps combined with the operator’s first-hand experience of the sites, to better describe the geological unit and age, along with other characteristics such as station installation and morphology. The third and largest step is to compile the first Greek ground-motion dataset on rock and perform a detailed analysis of the recordings to estimate site-specific transfer functions and hence assess local site response characteristics for each station. A strong-motion dataset of 6840 recordings is developed and curated for this purpose, visually inspected and processed in the time and frequency domains. Single-station amplification functions (horizontal-to-vertical spectral ratios, HVSR) are estimated from the seismic data, and the site resonance characteristics are assessed, not only in the conventional way of combining components, but also assessing directional sensitivity. ‘True’ reference site behaviour implying low, flat amplification with no directional dependence, these elements these transfer function characteristics are combined with the compiled existing and new metadata, to evaluated the stations’ capacity as reference sites. The stations are grouped in terms of behaviour and the preferred ones are recommended, hoping to facilitate the better use of data in future hazard applications.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Olga-Joan Ktenidou, Antonia Papageorgiou, Erion-Vasilis Pikoulis, Spyros Liakopoulos, Fevronia Gkika, Ziya Cekinmez, Panagiotis Savvaidis, Kalliopi Fragouli, and Christos P. Evangelidis

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on nhess-2023-233', Alexandra Moshou, 01 Feb 2024
    • AC1: 'Reply on CC1', Olga-Joan Ktenidou, 03 Jul 2024
  • RC1: 'Comment on nhess-2023-233', Chuanbin Zhu, 17 Mar 2024
    • AC2: 'Reply on RC1', Olga-Joan Ktenidou, 03 Jul 2024
  • RC2: 'Comment on nhess-2023-233', Giovanni Lanzano, 05 Apr 2024
    • AC3: 'Reply on RC2', Olga-Joan Ktenidou, 03 Jul 2024
Olga-Joan Ktenidou, Antonia Papageorgiou, Erion-Vasilis Pikoulis, Spyros Liakopoulos, Fevronia Gkika, Ziya Cekinmez, Panagiotis Savvaidis, Kalliopi Fragouli, and Christos P. Evangelidis
Olga-Joan Ktenidou, Antonia Papageorgiou, Erion-Vasilis Pikoulis, Spyros Liakopoulos, Fevronia Gkika, Ziya Cekinmez, Panagiotis Savvaidis, Kalliopi Fragouli, and Christos P. Evangelidis

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Short summary
Greek seismic data are valuable in European and even global databases, due to its high seismicity and numerous seismic stations. Seismic data coming from stations that lie on rock (i.e., not soil) sits are particularly valuable in seismology to define reference ground conditions and ground motions. However, little knowledge exists yet on how rock stations in Greece behave. This is the first time the network of the National Observatory is studied systematically to reveal reference stations.
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