Studio delle Proprietà Geotecniche e del Comportamento Dinamico dell Alta Valle del Crati nell Area Urbana di Cosenza

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1 Trieste, Novembre 2015 Studio delle Proprietà Geotecniche e del Comportamento Dinamico dell Alta Valle del Crati nell Area Urbana di Cosenza Maurizio Piersanti 1, A. Caserta 2, G. Galli 1, G. Carlucci 1, G. Della Monica 1 1 Università degli Studi RomaTre, Dipartimento di Scienze, Sez. Scienze Geologiche 2 Istituto Nazionale di Geofisica e Vulcanologia

2 Progetto Pon MASSIMO (Monitoraggio in Area Sismica di SIstemi MOnumentali) The MASSIMO project has the purpose to study and monitor the response of different types of constructions to seismic stress by different approaches Analysis of the seismogenetic sources; The surface geology, the topographic characteristics, the elastic properties of soils in relation to the monument architectural and static preservation; Monitoring and early warning products by using remotely sensed data (SAR and optical data); Earth monitoring products through aeromagnetic surveys; Monuments surveying (screening ) with proximal remote sensing instruments (laser scanner, thermal camera, sclerometer, georadar, sonic instruments, flat jack testing)

3 Geological Setting of the Study Area Crati Basin S. Agostino Church and Bretti&enotrii Museum test site Geological evolution of the Crati Basin: Metamorphic Bedrock Marine sediments on metamorphic bedrock Tectonics Fluvial erosion CASSA DEL MEZZOGIORNO ( ) Carta geologica della Calabria, scala 1:25.000

4 Arcavacata B&B Arcavacata HV Crati Basin Agriturismo B&B Piazza Haring Agriturismo Test Site Piazza Haring All the sites were studied using seismic noise array analisis (2D-1D arrays) in order to obtain a shear-wave velocity profiles

5 Results from seismic noise measurements: Bedrock Deepening Arcavacata B&B S Piazza Haring Agriturismo B&B Arcavacata N Agriturismo Piazza Haring m Test Site m LEGEND sands alluvial deposits bedrock sands and clays Dynamic models obtained with too small arrays to agree with HV picks at 0.4 Hz and 0.3 Hz, respectively

6 HV Test Site Area S3 High variability in resonance frequency Borehole site selection S4 S4 S3 test site S2 S2 Meters

7 Meters Geological Model of the Test Site Area NW SE S Crati River Test Site Busento River S3 S4 S2 A- alluvial sands S- marine sands sbg- biotitic-granatiferous schists S3 S4 test site Down-hole Test S2 High variability in bedrock velocities

8 depth (m) 0 Fill (R) Alluvial sands (A) 1 km S5 piazza Haring Site S5 20 Silts and Clays (SC) 40 Silty-Clayed Sands (SCS) silt with clays sands down hole F A SC SCS 100 silts with clayed sands Inversion Problem S2 120 sands Finding the position of the bedrock sbg

9 Bedrock Deepening N S5 210 m 1 km Piazza Haring 135 m sbg- bedrock 2 km piazza Haring S5 S Meters

10 Testing Liquefaction Risk S2 S5 Fill Fill Fill Alluvial deposits Alluvial deposits Alluvial deposits Silts and clays S3 Fill S4 Fill Simplified procedure by Andrus&Stokoee (2001) was applied for preliminary evaluation of liquefaction risk for all the study sites: Alluvial deposits Alluvial deposits Gravels CSR: Cyclic Stress Ratio CRR: Cyclic Resistance Ratio Acquifer level

11 depth (m) Site S5: RC and TTC Tests D (%) Undisturbed samples collected in borehole S5: 1. Identification of linear and volumetric thresholds 2. Decay law S5... Fill (R) Alluvial sands (A) Silts and Clays (SC) Silty-Clayed Sands (SCS) S5_C2 S5_C3 S5_C4 G/G ,2 1 0,8 0,6 0,4 0,2 0 0,0001 0,001 0,01 0,1 1 ϒ (%) S5_C4 ( m) proposed function G/G 0 =1/( ϒ% ) Finding a complete decay model: Ardin and Drevich (1972) in modified form after Yokota (1981) 0 0,0001 0,001 0,01 0,1 1 ϒ (%) S5_C4 ( m) proposed model D%=81.69 exp ( G/G 0 )

12 1D-Model: Site S5 Evaluate the seismic response of the study area Three synthetic reference earthquakes were applied to the metamorphic bedrock (sbg ) as seismic input: Ms = 7.0 with epicentral distance of 5.3 km, PGA of 0.46g, Ms = 6.0 with epicentral distance of 0.71 km PGA of 0.31g; Ms = 5.0 with epicentral distance of 18 km, PGA of 0.053g. TIBERTI M.M., et al. (Monitoraggio in Area Sismica di Sistemi Monumentali), Unità di Ricerca Analisi delle sorgenti sismogenetiche, Rapporto tecnico sugli stati d avanzamento intermedi (n.3 dal 01/06/2013 al 30/11/2013. Decay law level group lithology thickness (m) Vs (m/s) density (kg/m 3 ) Damping (%) I F fill II A alluvia III SC silts and clays IV SCS siltyclayed sands V sands VI S2 sands VII sbg altered bedrock VII sbg bedrock Half-space

13 1D-Model: Results Vertical deformation profiles versus depth Amplification functions: comparison between HV curves from seismic noise.

14 Conclusive Remarks 1. Geological reconstruction of the trend of the metamorphic bedrock in the High Crati Valley (seismic noise analysis, boreholes, lab Tests); 2. Testing Liquefaction Risk; 3. 1D-Model Outlooks Installation of permanent sensors inside the Test Site and down to the borehole depth to compare theoretical models