Lithospheric and Upper Mantle Stratifications Beneath Colombia: Using Receiver Functions from S Waves.

English Abstract:

The knowledge of the structure of the lithosphere is an important parameter to understand the evolution of the Earth and plate tectonics behavior. Seismic recordings of RSNC^*/IRIS^** stations are processed with S receiver function (SRF) technique to determinate the asthenosphere lithosphere boundary (LAB). The technique uses distant seismic events, 65° to 85° from the station, to detect the S wave and its Sp wave conversion at broadband-three component stations. To isolate the recorded phase is necessary to apply a rotation process to the components; this process takes the ZNE into the ZRT components through the back azimuth of the event, and then is necessary an extra rotation through the incident angle to obtain the LQT components. The L-component is almost free of the transverse energy from the S-wave and it is de-convolved from the Q-component to obtain the SRF. Once the FRS are gotten for all the events, it is performed a migration and move out correction to be able to stack the FRS. According to the distribution of the seismological stations, the structure of the lithosphere obtained is expected to be highly inhomogeneous; in fact the LAB depends on the azimuthal orientation. The results show that the LAB in Colombia is found between 90 and 120 km, the shallower is found under the stations located at the Caribbean Ocean and the subduction zone, whilst the deeper are on the continent. Also for each FRS appears two lobes in the records, showing two different structures that could be the Moho and the Conrad discontinuities.