Fault-Magma Interactions in an Early-Stage Continental Rift (Eastern Rift, Africa)

Sarah Jaye Oliva
Thursday, November 26, 2020 · 11:00 am
ESB 5104-06

Strain in magmatic rifts is accommodated by both faulting and magmatism, but little is known of the frequency of dike intrusions and the role of the magmatic system in the local stress field in early‐stage rifts. We use a new earthquake data set from a dense temporary seismic array (2013–2014) in the ~7‐Myr‐old Magadi‐Natron‐Manyara section of the East African Rift, which includes the carbonatitic Oldoinyo Lengai volcano that erupted explosively in 2007–2008. Using full moment tensor inversion and waveform cross-correlations, we conclude that magma‐involved seismicity probably occurs over eruptive and intereruptive cycles, suggesting that significant and persistent strain is accommodated by magmatic processes. We use analytical and numerical models of magmatic rift zones to simulate lithospheric deformation in the presence of magma bodies, crustal thinning, and topography to quantify the interactions between surface and subsurface loading on intrusions and fault kinematics in a rift setting. Our 3D static models of a weakly extended rift demonstrate how rift topography and the geometry of crustal thinning can guide magmatism and strain localization, highlighting the need for a three-dimensional treatment of rift kinematics.