Crustal context of the Fagradalsfjall eruption: shear-wave velocity structure of the Reykjanes Peninsular from receiver function analysis

Abstract

Detailed investigation into local seismicity and geochemical analysis of erupted products from the 2021-22 Fagradalsfjall eruption has already provided new insights into the deep magma plumbing system beneath the Reykjanes Peninsular. Here we focus on producing a detailed regional-scale shear wave velocity model of the Reykjanes to provide wider scale crustal context for these results. Utilising seismic data from 105 stations operated by numerous groups on the peninsular from 2013 to present day, we use recordings of distant teleseismic earthquakes to observe P to s converted phases that provide insight into crustal structure through receiver function (RF) analysis. The total data set of nearly 3000 RFs is computed in several frequency bands. Small subsets of RFs from common backazimuths and epicentral distances displaying high waveform similarity are jointly inverted with surface wave dispersion measurements to produce approximately 300 individual velocity models across the area. These are migrated to depth within a 3D volume to define a single regional velocity model. Major interfaces such as the Moho and base of the upper crust are extracted to produce maps of peninsular wide variation. Computed velocity model inversion results are compared to  RF waveforms combined in multi-phase common conversion point stacks. We compare the velocity structure and interface depths extracted beneath Fagradalsfjall to magma depth estimates from geochemistry and potential structural changes hypothesised from local seismicity linked to the 2021-22 eruption.