Strain Accommodation and Displacement of the Lake Malombe Basin Border Faults in the Malawi Rift from Electrical Resistivity Imaging

The magma-poor Malawi Rift is located at the southernmost part of the western branch of the East African Rift System. The Malawi rift extends to the south for 750 km and bifurcates in the south into a western and eastern branch around the Shire Horst. Most of the strain appears to be accommodated across the eastern branch defined by the Malombe Basin. Lake Malombe basin is located south of Lake Malawi in the central region. This basin is approximately 70km in length and 35km wide, with border faults striking roughly N-S. The border faults of the Malombe basin remain largely understudied. The objective of our study is to investigate how strain is accommodated along the border faults and to more accurately estimate the displacement of each border fault. To complete this objective we acquired electrical resistivity data along exposed fault scarps bounding the Lake Malombe basin. We used both dipole-dipole and Wenner-Schlumberger arrays with a 10 m electrode spacing for a total length profile of 710 m. Our results show that the fault scarps are approximately 600 m in the west and 500 m in the east. Resistivity data shows resistive signatures associated with the uplifted footwall block. The hanging wall is characterized by a low resistivity layer at the top and a restive layer at the bottom. We interpret the low resistivity layer as the result of alluvial sediments and the lower resistive layer as the down thrown hanging wall. Our expected results are to calculate the minimum displacement for each border fault. Additionally, this work will show the geometry of the buried scarp. This provides interesting controls for the formation of both the Lake Malombe basin and the evolution of the Malawi rift.