A dense small-scale seismic network in the Ngorongoro Conservation Area (northern Tanzania)

Laura Parisi*1, P. Martin Mai1

1PSE Division, King Abdullah University of Science and Technology, Saudi Arabia (laura.parisi@kaust.edu.sa)

A temporary deployment consisting of seventeen broadband seismic stations was conducted between June 2016 and May 2018 in the Ngorongoro Conservation Area (NCA, Northern Tanzania), located at the boundary between the Tanzanian Craton and East African Rift. A deep knowledge of the tectonics of the area is needed to better understand the contribution of the synsedimentary faults to the deposition of the Olduvai and surrounding basins affecting the landscapes of the Homo Habilis first settlements.  Complex fault systems have been mapped in the field but their connection, especially at depth, is not well known.

Stations were equipped with Nanometrics Trillium Compact Posthole 120 s sensor and Centaur digitiser recording continuously at 200 Hz. The whole network covered 1400 km2and station interspace ranges from 8 to 15 km. We analyse probabilistic power spectra densities of the seismic noise to obtain insights of its origin and test the performances of the stations.

We also present the first seismicity map of the NCA. We detect events with ML ranging between 0.7 and 3.3. While the well-known faults in the northern part of the NCA show a very low seismic activity, the southern part of the NCA, where major fault systems have not been mapped at the surface yet, shows a moderate level of seismicity. The link between newly imaged faults and the active rift is still not clear.