The CORSSA Vertical Array Rift Soft Soil Array Infrastructure and Scientific Results

Zafeiria ROUMELIOTI1, Ioannis KASSARAS2

1Research Unit of Soil Dynamics and Geotechnical Earthquake Engineering, Dept. Civil Engineering, Aristotle University of Thessaloniki 2Dept. Geophysics-Geothermics, University of CORinth Soft Soil Array (CORSSA) LOCATION

EUROPROTEAS

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CORSSA

Installed in the frame of EU project CORSEIS, the first in a series of projects that led to the development of the Corinth Rift Laboratory (CRL; http://crlab.eu/) CORSSA Array & Geotechnical Model

Layout of the sensors of the vertical array and gross geotechnical model (Apostolidis et al., 2006)

Formation Geological Description Thickness NSPT VS Code (m) (m/sec) A Soft marine deposits consisting of sandy 20 8-14 180 silt, silt and clay B Soft sediments: clayey silt, sandy clay, 25 14-20 265 silty clay, with few gravels C Hard deposits: clayey silt, sandy clay, 55 30-45 440 silty clay, with few gravels D Very hard deposits: sandy gravels, sandy 55 >80 540 clay with few gravels E Stiff conglomerate - - 1000 Recorded Seismicity (2002-2012) CORSSA Data

716 acceleration records

ML=1.15-6.5 R=1-281 km CORSSA Web Portal: www.corssa.gr

Kassaras et al., 2016 CORSSA Data-based Publications:

• PhD Thesis: Ktenidou, O.-J. (2010). Experimental and theoretical study of seismic ground motion in the city of Aegion, Greec, focusing on local site and topographic effects, Aristotle University of Thessaloniki.

• Ktenidou et al. (2013) A study on the variability of Kappa (κ) in a borehole: Implications of the computation process. Bulletin of the Seismological Society of America. Seismological Society of America. pp. 1048-1068. ISSN 0037-1106 ISSN 0037-1106 • Ktenidou et al. (2016) Directional dependence of site effects observed near a basin edge at Aegion, . Bulletin of Earthquake Engineering. Springer Verlag. pp. 623-645. ISSN 1570- 761X ISSN 1570-761X • Kassaras, I., Z. Roumelioti, O.-J. Ktenidou, K. Pitilakis and K. Makropoulos (2016). Accelerometric data and web portal for the vertical Corinth Gulf Soft Soil Array (CORSSA), Proc. of the 14th International Conference of the Geological Society of Greece, 25-27 May 2015, Thessaloniki, Greece. • Roumelioti et al. (2018) Shear wave velocity variations at the CORSSA (Central Greece) vertical array, Proc. of the 16th European Conf. on Earthq. Eng. (16ECEE), 18-21 June 2018, Thessaloniki, Greece. Shear Wave Velocity Variations at the CORSSA (Central Greece) Vertical Array

Zafeiria ROUMELIOTI1, Fabrice HOLLENDER2, Philippe GUEGUEN3

1Research Unit of Soil Dynamics and Geotechnical Earthquake Engineering, Dept. Civil Engineering, Aristotle University of Thessaloniki 2CEA/DEN, 13108 Saint Paul Lez Durance, France // ISTerre, University Grenoble-Alpes / CNRS / IFSTTAR / IRD / USMB, France 3ISTerre, University Grenoble-Alpes / CNRS / IFSTTAR / IRD / USMB, France Seasonal Variation of Vs: 6-7% (lower bound)

Monthly mean Vs variation

Monthly mean rainfall (Triantou, 2011) Azimuthal Variation of Vs Values: 6-7%

Deep Anisotropy Prioul et al. (2004)

 Lampiri

 Kamares r ive Loggos R  nix SF oe Ph ?  ?

FF  Rododafni Neratzies 

Aliki CORSSA Lagoon Bay r  e iv R AF i s Aigio it n a g e M Variation of Vs Due to Nonlinear Response of the Soil (~20%)

10 Jan 2009; ML4.1; R = 54 km; Baz = 241° CORSSA

EQ. Epicenter

08 June 2008; ML6.4; R = 58 km; Baz = 238° CORSSA

EQ. Epicenter Variation of Vs Due to Nonlinear Response of the Soil (~20%)

Vs Variation:

 Precipitation  seasonal cycling with lower Vs during wet periods and higher Vs during dry periods. Vs variation is of the order of 6-7% within the top 15m but is expected to be quite larger at shallower depths

 Azimuth within the soil formations  Fast-shear and low-shear sectors; Soil formations distort the incoming anisotropy

 Level of excitation  lowering of Vs during strong shaking Current Status of the CORSSA Facility

• Not in operation • Need for an upgrade of the recording system (Mt. Whitney – Kinemetrics) • Boreholes, sensors and the shelter of the surface equipment are in good condition