Investigating the effects of topography and magma reservoir structure on volcano-tectonic interactions in a youthful continental rift

Abstract:

Previous studies of active volcanic rifts have provided evidence that various localized geochemical and geophysical interactions may influence future magmatic and faulting events. In our previous work, we investigated stress interactions during the 2007-2008 Tanzanian rifting crisis in the Natron Rift and demonstrated that small stress changes (< 0.1 MPa) could promote slip on a major border fault, the Natron Fault. In this work, we use the 3D finite element code PyLith to investigate volcano-tectonic interactions in the Natron Rift by evaluating stress interactions between the active carbonatite volcano Ol Doinyo Lengai and the adjacent Natron Fault. We hypothesize that stress changes on the Natron Fault due to magma reservoir volume changes from Ol Doinyo Lengai play a dominant role in promoting or inhibiting slip during early phase rifting in this region when compared to the effects of topographic loading. We perform a suite of experiments to systematically test the effects of magma reservoir size, volume change, and topography for a deflating magma chamber beneath Ol Doinyo Lengai on the stress state of the Natron Fault and compare predicted surface displacements with GPS observations. Our preliminary results suggest the size of the deflating magma reservoir plays the more important role in influencing the magnitude and patterns of stress changes on the Natron Fault, which implies volcanic deformation can promote fault slip during early phase rifting.