The M5.0 Turkana Rift Mainshock-Aftershock Sequence, E. Africa

The volcanically and seismically active Main Ethiopian and Eastern (Kenya) rifts are linked in a complex zone within the Turkana Depression bounded by the Ethiopian plateau to the north and East African plateau to the south. Subsurface imaging beneath Lake Turkana and surrounding sub-parallel basins reveals multiple half-graben basins bounded by N-S striking normal faults. Lake Turkana includes at least 3 Quaternary volcanoes within the central rift basins. The 32-station Turkana Rift Array to Investigate Lithospheric Structure (TRAILS) project recorded the May 3, 2020 M5 event and its aftershocks. Our objective is to use the mainshock and aftershock distribution to analyze the main rupture fault plane and surrounding minor rupture planes. The aftershock occurrence is related to Omoris Law which explains the rate at which they decay, and it informs probabilistic hazard models. The TRAILS data and a permanent GEOFON station, LODK, are used to relocate the mainshock and aftershocks, and determine the focal mechanism solutions for the largest events. The data is analyzed using SEISAN software to precisely relocate the events using double difference methods and obtain the fault plane solutions. The aim of this analysis is to develop improved statistical models for assessing earthquake hazards and do a comparison of the earthquake locations to mapped syn-sedimentary and basement faults.