Structure of the Laguna del Maule Volcanic Complex, Chile, using teleseismic receiver functions

Abstract:

Uplift at the Laguna del Maule volcanic field (LdM) in the Southern Andes of Chile since 2007 occurs at a rate of >20 cm/yr (Fournier et al., 2010; Feigl, et al. 2014; Le Mevel et al., 2015; 2016). The location and dimensions of the subsurface source of uplift are not yet well constrained. Models based on InSAR interferograms estimated the uplift source to be a ~45 km² sill located at ~5 km depth (Feigl et al., 2014; Le Mével et al., 2015, 2016); surface wave tomography indicates a low-wavespeed anomaly at ~1.5-7 km depth near the center of inflation (Wespestad, 2017). In this study we use approximate source dimensions and forward modeling of expected receiver function waveforms to test the applicability of receiver function analysis to further constrain the subsurface magma chamber, and we show preliminary receiver functions sorted by back-azimuth and incidence angle. The preliminary receiver functions were calculated for 11 seismic stations using earthquakes > M6 between 30-90 degrees, a total of 233 events. Preliminary results show the main Ps phase at ~7 s consistent with a Moho at ~50 km. Current work focuses on modeling seismic phases arriving before the Moho phase, possibly related to the magmatic system. Receiver functions from the additional 37 stations and from the full two years of data (once acquisition is complete in early 2018) will increase the number of back-azimuths and angles available, and thus increase the probability that paths will cross through the spatially restricted source feature.