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Avellanes seismic station (CAVN)

Code: CA.CAVN Name: Les Avellanes 

Latitude: 41.8815 N Longitude: 0.7506 E Height: 634 m

Local depth: - m

Owner: Institut Cartogràfic i Geològic de Catalunya

Subsoil features

Lithology

Period

Vs30 (m/s)

Classe EC8

F0 (Hz)

Lutites and carniola gypsums

Triassic

891

E

6.0

Instrumentation by channels and periods

Channels

Start date

Sensor type

Digitizer type

Instrumental response

HHZ, HHN, HHE

01/06/1999

Broadband velocimeter

24 bits

[StationXML]

Geophysical characterisation

H/V Spectral ratio from seismic noise

H/V Spectral ratio from seismic noise records of Les Avellanes seismic station. A peak around 6 Hz is observed which can be related to the soil fundamental frequency and, therefore, a contrast of acoustic impedance in the subsoil is expected.

H/V Spectral ratio curve using seismic noise records from Les Avellanes seismic station.

H/V Spectral ratio curve using seismic noise records from Les Avellanes seismic station.

P-waves velocity  model

The P-waves velocity model, obtained by seismic tomography technique, provides information of the subsoil up to 12 meters depth. A first layer is observed, about 8 meters thick, characterized by velocities lower than 2500 m/s that is interpreted as an unconsolidated soil. The underlain layer withf higher velocities (Vp>3000 m/s) is associated with non-rippable fresh rock.

P-waves velocity model of Les Avellanes seismic station, obtained by seismic tomography technique.

P-waves velocity model of Les Avellanes seismic station, obtained by seismic tomography technique.

S-waves velocity model

From the surface waves analysis (MASW) a vertical shear wave velocity profile (Vs) is retrieved. Three layers are identified: (1) a near-surface layer about 2 meters thick with a very low velocity (Vs=225 m/s) is observed, which indicates the presence of uncompacted material, related to the presence of filling material; (2) then we find a low velocity zone (Vs=650 m / s) that reaches 8 meters depth and that is interpreted as an unconsolidated soil; (3) the underlain layer is characterized by and a velocity increment (Vs>2000 m/s) that is associated with non-weathered rock.

S-Waves velocity model of Les Avellanes seismic station, obtained from the analisi of surface waves (MASW).

S-Waves velocity model of Les Avellanes seismic station, obtained from the analisi of surface waves (MASW).

Electrical tomography

The geoelectrical model resulting after inverting the electrical resistivity (electrical tomography) shows a structure of three layers that can be related to changes in propagation velocity: (1) a first resistive layer of 2 meters thick (1000-2000 Ω·m) that correlates with the low-velocity and low-compacted stratum; (2) a second layer of medium resistivity (200-400 Ω·m) that reaches 8 meters depth and that is associated with unconsolidated soils, and finally, (3) a resistive layer is detected (500-3000 Ω·m) related to the velocity increase and interpreted as bedrock. 

Surface electrical resistivity model with the location of Les Avellanes seismic vault

Surface electrical resistivity model with the location of Les Avellanes seismic vault