Magma-tectonic interactions within Tanzania's Natron Basin constrained from satellite geodesy and seismicity
Open Access
- Author:
- Ho, Cristy
- Graduate Program:
- Geosciences
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 02, 2023
- Committee Members:
- Donald Fisher, Program Head/Chair
Christelle Wauthier, Thesis Advisor/Co-Advisor
Andrew Arnold Nyblade, Committee Member
Sridhar Anandakrishnan, Committee Member - Keywords:
- Natron Basin
Ol Doinyo Lengai
Gelai
volcano
Naibor Soito volcanic field
InSAR
InSAR time series
MSBAS
geodesy
seismicity
Coulomb stress change
volcanic deformation
crater
fissure
earthquake swarm
sill complex
rift - Abstract:
- Young active rifts experience complex interactions between volcanic activity, magmatism, seismicity, and faulting. An ideal location to study these processes is the Natron Basin in northern Tanzania, which lies on the eastern branch of the East African Rift System. The western side of the Natron Basin contains Ol Doinyo Lengai, the only volcano in the world that erupts carbonatite lava. To the east is an active field of monogenetic cones called the Naibor Soito volcanic field, and Gelai, a shield volcano that has not erupted since the Pleistocene. Although Gelai is dormant, the volcano experienced a magma-driven earthquake swarm and dike intrusions in 2007 right before the Ol Doinyo Lengai explosive eruptions which spanned 2007-2008. Evidently, investigating the entire Natron Basin is important because Ol Doinyo Lengai and Gelai are connected to an extensive magmatic plumbing system centered at an inferred sill complex beneath the Naibor Soito volcanic field. This study involves the analysis of temporally dense SAR datasets spanning 2013-2014 and 2018-2020 that overlap with available seismic catalogs. All 767 interferograms of the entire Natron Basin did not show clear deformation patterns. However, InSAR time series revealed subsidence at the North Crater near the summit of Ol Doinyo Lengai. The subsidence is likely related to the growth of a fissure on the western side of the crater and a potential ring fault system. The magma reservoir beneath Ol Doinyo Lengai was modeled using a Mogi point-source at 3 km depth based on prior studies, however results suggest that the magma reservoir is located at a shallower depth. Although the Natron Basin experienced frequent seismicity during the two investigation periods, the largest earthquakes did not cause noticeable surface displacements. Even so, the Naibor Soito volcanic field experienced many earthquakes, suggesting activity in the sill complex. Focal mechanisms were used as receiver faults to calculate Coulomb stress changes caused by a 10 km deep sill with an opening of 2 m, which could have triggered earthquakes.