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Garraf seismic station (CGAR)

Code: CA.CGAR Name: Garraf 

Latitude: 41.2933 N Longitude: 1.9137 E Height: 584 m

Local depth: 0.5 m

Owner: Institut Cartogràfic i Geològic de Catalunya

Subsoil features

Lithology

Period

Vs30 (m/s)

Classe EC8

F0 (Hz)

Limestones and marlstones 

Early Cretaceous (Berriasian) 

1993

A

-

Instrumentation by channels and periods

Channels

Start date

Sensor type

Digitizer type

Instrumental response

HHZ, HHN, HHE

01/08/2001

Broadband velocimeter

24 bits

[StationXML]

Geophysical characterisation

H/V Spectral ratio from seismic noise

H/V Spectral ratio from seismic noise records of Garraf seismic station. It is observed an almost flat curve, without any significant peak which might be associated to  the fundamental frequency of the soil. This behaviour is typical of rock sites.

H/V Spectral ratio of seismic noise records of Garraf station.

P-waves velocity  model

The P-wave velocity model, obtained by seismic refraction  tomography, is characterized by a strong velocity gradient, which goes from the surface, where 1000 m/s are detected, to about 5 meters deep, where it exceeds 3500 m/s. In the sector of the seismic station, velocities higher than 2500 m/s are reached at a depth of about 3 meters. These high velocity values ​​are associated with unweathered non-ripable rock, and can be interpreted as the bedrock.

P-waves velocity model of Garraf seismic station.

S-waves velocity model

In the shear wave (VS) propagation velocity model obtained by seismic refraction  tomography, high velocities are observed near the surface. In the area of ​​the seismic well the bedrock is reached (VS = 1000 m/s) to 2 meters of depth, and to 4 meters of depth the isoline of 1500 m/s is detected, that usually is associated to very hard rock .

S-waves velocity model of Garraf seismic station.

Images

4 multimedia

General view of different elements: Instrumental house, VSAT antenna and geodetic pillar.