| dc.description.abstract | During two field campaigns in 2007 and 2010, long-period and broadband magnetotelluric measurements
were conducted in the Central Andes of northern Chile and northwestern Argentina at a latitude of 23.7°S.
The study area spans from the Precordillera over the active volcanic arc of the Western Cordillera until the
western part of the Puna. A special focus was on Lascar, a subduction related stratovolcano with an historical
activity characterized by fumarolic emissions and occasional sub-plinian eruptions, like the one occurred on
1993. The broadband instruments, covering a period range between T=0.005 s and 1000 s, were installed in
the proximities of Lascar volcano, while the long-period devices (T=10 s–10,000 s) were installed on a profile
slightly south of Lascar, crossing the Salar de Atacama basin, the volcanic arc and reaching the western
border of the Puna.
Remote reference and robust techniques were used for data processing. Induction vectors, phase tensor ellipses
and strike direction of the conductivity distribution were calculated, showing some 3-D behavior for the
Lascar sites at shallower depths, with induction vectors close to the edifice influenced partially by the topography.
3-D modeling and inversion revealed conductive anomalies beneath Lascar volcano, but also beneath
the Puntas Negras volcanic chain. For the long-period transect, the behavior is closer to a 2-D case, with
more stable strike direction coherent with induction vectors and phase tensor ellipses. The major result of
2-D inversion is a vast high-conductivity zone in the backarc crust, which seems to be the southern extension
of a large highly conductive anomaly observed in prior studies beneath the Altiplano. | |
