THE INFLUENCE OF THE RED SEA RIFTS AND THE GULF OF ADEN RIFTS ON THE
LATERAL PROPAGATIONS OF FAULTS IN THE DOBI GRABEN AND ITS SURROUNDING
AREA IN THE AFAR DEPRESSION
Abstract
The Dobi graben is a NW-trending, Quaternary continental rift found
within the East-Central Block (ECB) of the Afar Depression (AD) in
northeastern Ethiopia. Extension occurs on steeply dipping faults, where
the ratio of maximum displacement to traced fault length extends to four
orders of magnitude. We conducted fault population analysis in the Dobi
graben using a 30 m resolution Shuttle Rader Topography Mission (SRTM)
Digital Elevation Model (DEM). We traced a total of 953 faults. We used
the fault displacement length profiles’ tapering directions and the
different types of fault propagations’ termination styles to
characterize the fault kinematics pattern. Our population analysis
results show that ~45% of the normal faults in the Dobi
graben are tapering towards the southeast in a manner similar to the Red
Sea Rift (RSR) regional strain gradient. On the other hand, our analysis
showed that ~40% of the faults in the Dobi graben are
tapering towards the northwest direction in a manner similar to the Gulf
of Aden Rift (GAR) regional strain gradient. We found the statistical
regression correlation coefficients (R-square value) for both the
southeast and the northwest tapering faults to be ~0.7.
Therefore, we suggest that ~85% of the lateral
propagation of the 953 faults in the Dobi graben is highly influenced by
the regional strain transfer of the RSR and GAR. Additionally, based on
the fault propagation termination styles, our faults population analysis
shows that faults which exhibit the half-restricted termination style
account for 85% of the 953 faults. The maximum displacement over the
maximum length (Dmax/Lmax) ratio of these faults is 0.03, which is in
accord with the constant displacement length fault growth model.