Shear-wave velocity anomalies in Southern Andes within latitudes 35°S and 37°S: model and interpretations from seismic ambient noise
Abstract
The volcanic arc of the Southern Andes is linked to the oblique convergence of Nazca plate beneath the South American plate (subduction velocity of ∼ 66 mm/yr). The volcanic arc accounts for about sixty active volcanoes of Pleistocene-to-Holocene ages. Here we present a regional-scale (i.e. 35°S and 37.5°S) Rayleigh surface-wave tomography from seismic ambient noise that highligths the three-dimensional shear-wave velocity structure at crustal depths. This study is, to the best of our knowledge, the first attempt of a regional-scale Ambient Noise Tomography of a volcanic arc. We find that velocity anomalies are in agreement with the geological setting and the spatial distribution of the present-day volcanoes. The crystalline Cenozoic basement, represented by the outcrop of Mio-Pliocene plutons shows high-velocity anomalies greater than 3%. On the other hand, Descabezado Grande, Puelche and Laguna del Maule volcanic fields show low-velocity anomalies ranging within 3 - 6% located at 5 - 10 km depth. Nevados de Longaví, Chillán and Antuco volcanoes also show strong low-velocity anomalies. We interpret that mid-crustal low-velocity anomalies are associated with a mechanically weakeaned regions, due to a high porous crust or, the presence of fluids and thermal anomalies.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2017
- Bibcode:
- 2017EGUGA..1910839G