Multi-scale Imaging of Iceland using Ambient Noise and Teleseismic Earthquakes

Iceland is one the most active tectonic regions in the world. While previous seismic tomographic models have provided insights into subsurface structure, rifting and the presence of a mantle plume and melt, these models have lacked the multi-scale resolution to connect the near surface and crustal structure to the mantle. In order to advance our understanding on the lithospheric structure and how it relates to geothermal activity we require a high resolution full lithosphere model of Iceland.

 

Using recently acquired passive seismic data, we are constructing a new surface wave velocity model of Iceland by combining ambient noise and teleseismic earthquake data derived from phase velocity dispersion. We use a database of 205 seismic stations from a variety of permanent and temporary networks recorded between 1993 and 2024. We obtain  Rayleigh and Love phase velocity dispersion curves from the cross correlograms using SeisLib (Magrini et al., 2022). For teleseismic earthquakes, we measure phase variation between nearby stations using a waveform cross-correlation method. We perform strict quality control to ensure that the dispersion measurements are robust since the instruments used are of different sensitivities, affecting the dispersion measurements at longer periods. The dispersion curves and phase variations are inverted for phase velocity maps between 4 – 100 seconds period.

 

We observe low velocity in the upper and mid crust around the Western Volcanic Zone (WVZ), Eastern Volcanic Zone (EVZ) and Northern Volcanic Zone (NVZ) following closely with the rifts in Einarsson et al. (2006), and significantly lower velocity around the western edge of the Vatnajökull icecap. We also observe low velocity in central Iceland in the lower crust and upper mantle. We invert the phase velocity maps for shear velocity models of the lithosphere. This new model will contribute to providing high resolution imaging of the Icelandic lithosphere from the crust to mantle. We will in future jointly invert the velocity model with petrological data to model the geothermal structure of Iceland with a local focus at the Krafla volcanic complex.