Crustal and Uppermantle Velocity Structure of Greenland from Ambient Noise and Earthquake Surface Wave Tomography

Abstract:

We present a seismic tomography model of Greenland from surface wave analysis. Data from regional and teleseismic events with magnitude greater than Mw 5 and recorded over the last 15 years were used. In addition, in order to better constrain the crustal structure of Greenland, we also collected and analyzed two years (2013-2015) of ambient noise data. The empirical Green’s functions for all interstation paths were calculated by ambient noise cross-correlations. A frequency-time analysis technique is applied to measure the group velocity dispersion curves of the fundamental mode Rayleigh wave for periods ranging from 20 to 200 s for earthquake data and 10 to 50 s for ambient noise. In order to focus on the group velocity dispersions within the region of study, we used a global dispersion tomography model from Ekström et al. (2011) for the path outside of our region. Assuming an isotropic structure and using a generalized least-square approach, the dispersion curves are inverted to produce group velocity maps at several discrete periods. The results of the group velocity inversion are used to build localized dispersion curves in 1° by 1° cells. A Markov chain Monte Carlo technique is then applied to invert the localized curves and estimate shear wave velocity models of Greenland up to depths of 200 km where surface wave sensitivity to shear wave velocities is large. Detailed velocity models of Greenland’s lithospheric structure should help constrain the source of a high geothermal heat flux observed in northeast Greenland and provide valuable information about the geology within Greenland’s continental margin which has previously only been sparsely investigated. All the data are obtained from the GLISN and the GSN networks. We thank the operators of these stations for their open access to the data.