La Rabassa seismic station (ARBS)
Code: CA.ARBS Name: La Rabassa Latitude: 42.4344 N Longitude: 1.5337 E Height: 2145 m Local depth: 30 m Owner: Institut d'Estudis Andorrans |
| Soil features | ||||
|---|---|---|---|---|
| Lithology | Period | Vs30 (m/s) | Classe EC8 | F0 (Hz) |
| Slates | Upper Ordovician | 476 (0 m) >1014 (-27 m) | B (0 m) A (-27 m) | 1.5 (0 m) 2.5 (-27 m) |
| Instrumentation by channels and periods | ||||
|---|---|---|---|---|
| Channels | Start date | Sensor type | Digitizer type | Instrumental response |
| HHZ, HH1, HH2 | 01/10/2009 | Broadband velocimeter | 24 bits | [StationXML] |
Geophysical characterisation
H/V Spectral ratio from seismic noise
H/V Spectral ratio using seismic noise records from La Rabassa seismic station, with sensor installed 30 meters deep. A peak around 2.5 Hz is observed that can be related to the fundamental frequency of the ground. Therefore, an acoustic impedance contrast is expected.
H/V Spectral ratio of seismic noise records from La Rabassa seismic station
P-waves velocity model
The P-waves velocity model, obtained by seismic tomography technique, is characterized by significant lateral variations along the seismic profile. A package of low-velocity materials (VP <2000 m/s) is observed that extends to almost 30 meters deep and is located only 5 meters deep on the northwest side of the profile. The depth of investigation of the seismic profile, with a maximum of 30 meters, is not sufficient to detect materials with velocities greater than 2500 m/s, which are usually associated with unweathered non-ripable rock and which can be interpreted as the bedrock.
P-waves velocity model of La Rabassa seismic station
S-waves velocity model
In the shear wave propagation velocity (VS) model obtained by seismic refraction tomography it is characterized by an extensive layer of low velocity materials (VS <1000 m/s) with variable power. The depth of the isolines that is usually interpreted as the bedrock (VS = 1000 m/s) varies between about 40 meters on the southeast side of the seismic profile and less than 15 meters at the northwest end of the profile. Even, a superficial layer of unconsolidated materials (VS <500 m/s) of a 10-meter thickness is observed. In the seismic well area, the bedrock (VS = 1000 m/s) is located at a depth of approximately 40 meters.
S-waves velocity model of La Rabassa seismic station