Patterns of cumulative and incremental fault growth in a magmatic continental rift; Manda- Hararo Rift, Afar, Ethiopia.

Abstract

A digital elevation map constructed from LiDAR imagery of the Manda-Hararo rift, Afar, Ethiopia, was used to investigate structural trends and patterns of growth for 306 normal faults in that area. Using ESRI’s ArcMap programme, faults and fault linkages were selected and properties of these structures, such as fault length, maximum offset, D-L ratios, elevation and offset profile symmetry were determined. This allowed for comparisons between different structural elements, as well as comparisons between fault properties and other features of the rift, such as the presence of volcanic edifices, the extent of the recent rifting episode, and the propagation and effect of dike injection associated with that episode. Few significant relationships could be found between properties of faults in the rift barring fault length and maximum offset, which show the same positive power-law relationship as explored in other works. Volcanic edifices were observed to have a minor effect on the orientation of faults in their vicinity, and there was discovered a slight difference in distribution of types of fault linkage. Faults mapped in this study did not show any morphology that may reflect the direction and timing of subsurface dike propagation. This could suggest that the magma source for diking events in the Manda-Hararo rift is changeable, and has not been at its current location for long enough that the cumulative offset on the regions faults refects the preferential direction of propagation of dikes from that source.