Ambient seismic noise tomography of the Colima Volcano Complex

The Colima Volcanic Complex (CVC) located in the western sector of the Trans-Mexican Volcanic Belt contains the most active Mexican volcano, Volcan Colima. The CVC is located within the Colima Rift, a regional north south striking extensional structure. We used ambient seismic noise recorded by stations deployed in western Mexico during the Mapping the Rivera Subduction Zone (MARS) and the Colima Volcano Deep Seismic Experiment (CODEX). We computed the cross-correlations of the vertical component of continuous records of ambient noise data to extract empirical Greens functions. These functions provide detailed images of Rayleigh wave group velocity for different periods. Using the arrival travel time of these waves for a given period, estimates can be obtained of the lateral variations in velocity for a given period using 2D tomography. The study aims to better understand the geometry and the seismic surface wave velocity structure of the CVC and relate it to the volcanoes' structure and the geologic setting of the region. Source of low velocity anomaly over CVC is distributed fairly continuously with depth in the subsurface, which indicates magma rising along fractures. The progressive increasing toward the south in the size of low velocity anomalies indicates migration towards the south of the melting that correlates with the trend of the stratovolcanoes that form the CVC. The zone of magma generation presently fully developed under Volcan de Fuego might be starting to shift towards south to the area NW of Armería where a new void in the tear zone may be starting to form.