Miriam Gauntlett

I am a DPhil student under the supervision of Mike Kendall. My research uses seismological observations to elucidate and understand the structure and dynamics of the crust, both on a local scale at volcanoes and on a regional scale. This has involved local earthquake velocity tomography at Nabro volcano in Eritrea; and receiver function and shear-wave splitting analyses at stations near the Afar Triple Junction.

Seismic tomography work at Nabro volcano

I carried out a seismic tomography study of Nabro volcano using a catalogue of earthquakes located by machine learning methods immediately following its unexpected June 2011 eruption. 3D seismic modelling of P- and S-wave velocities revealed the structure of Nabro’s magmatic and hydrothermal systems. My observations identified the continued presence of magma in the primary melt storage region that fed the eruption and found that degassing from the magma storage zone caused overpressure in the partially-saturated, fractured intrusive complex above. The novelty of this research lies firstly in the use of a seismic catalogue produced by a deep learning model, which has never been used as an input before in a seismic tomography study. Furthermore, it is rare to observe the post-eruptive state of a volcano, particularly one in the understudied East African Rift System. Nabro was almost completely unmonitored prior to its eruption. Other than this work, no seismic tomography studies exist for any volcano in the ~110 km long Nabro Volcanic Range. I thus provide crucial insights into the subsurface structure of a recently erupted volcano in an understudied tectonic setting. This research has been published in the Journal of Geophysical Research: Solid Earth (https://doi.org/10.1029/2022JB025742).

Receiver functions and SKS splitting in Eritrea 

I am also interested in using seismology to quantify regional volcanism and tectonics. To better understand the nature of the Eritrean crust and continental breakup, I calculated teleseismic receiver functions across Eritrea and Afar, estimating the Moho depth and bulk crustal V_P/V_S ratio for each station using the H-κ stacking method. The results provided insights into the crustal structure and composition of Eritrea and the Danakil microplate; in particular, that magma-assisted extension continues to be important in the final stages of continental breakup. I used the relationship between crustal thickness and topography to determine that the Eritrean crust is denser than average continental crust, and that the hot mantle plume beneath Africa is likely to be responsible for the strong positive residual topography in the region. I have submitted this as a publication to Earth and Planetary Science Letters, where it is now under review. Seismic anisotropy measurements offer constraints on rift processes, absolute plate motions and tectonic structure. I calculated SKS shear wave splitting parameters beneath the regional Eritrean stations and am using these observations to infer the causes of mantle anisotropy in the region. This work is currently being prepared for publication.

I am funded by NERC via the Oxford Environmental Research DTP.