Gravity Transects across the Karonga Fault in the Northern Malawi Rift

Abstract:

The Karonga area of northern Malawi is in the hanging wall of the Livingstone border fault. While most of the strain is accommodated along the border fault, recent seismicity and remote sensing studies indicate there is strain accommodation in the hanging wall area. Gravity data were collected along two West-East transects (one in the north and the other in the south) in this region to explore this strain accommodation, locate faults, determine the thickness of sediments on the hanging wall block of the Karonga fault, and to determine the geometry of a Karoo depositional basin. Both profiles extended from the uplifted basements into the rift basin; the northern profile is approximately 30 km in length while the southern profile is 70 km. Both gravity profiles were acquired with a Scintrex CG-5 Autograv using station spacings ranging between 0.5 – 2 km. These gravity transects place constraints on the structural interpretations of the area based on previous fieldwork and remote sensing. This project uses 2.5D forward gravity modeling to test the possibility of the Karonga fault being a single fault in the north while breaking up into multiple faults further south as it responds to the weaknesses created by preexisting structures.