Analysis of the Inter-Diking Deformation Pattern at the Ongoing DabbahuManda Hararo (Afar), Ethiopia Rift Segment Using GPS and InSAR Technique

The Afar Depression, in the northeastern part of Ethiopia, offers unique opportunities to study the
transition from continental rifting to ocean floor spreading. This process, which is the outcome of
tectono-magmatic events, has been under investigation using different geophysical and geological
techniques. The current study mainly focused on GPS and InSAR methods to analyze the inter-dyking
deformation pattern along the Dabbahu-MnadaHararo (Afar) rift segment. The InSAR data was used to
identify the time of dyke events and the GPS data to study the inter-diking deformation pattern.
Asequence of 12 dyke events occurred from June 2006 to June 2009 and based on the GPS data two
major pattern of deformation have been identified. These are being categorized into before and after
June 2009 dyke events. Most of the GPS stations before June 2009 showed larger displacement rate
whereas after June 2009 intrusion, the displacement in most of the stations was relatively smaller. Even
though the deformation process is still active, sites such as DAFT, DA45, DAYR and DATR indicated that
the displacement rate is relatively stabilizing in the post seismic relaxation period. Moreover, sites such
as,DA25 and DA35, had large offsets in their time series right at the time of dyking events, which is an
indication of major deformation due to the rifting process. Except the distant sites DA60 and DASM all
the other stations were mostly affected by the dyke intrusion, such that there was an offset in the data
during the dike intrusion. Stations DA25, DA35, DA45, DA60, DAFT and DAYR that are located in the west
side of the rift, where the 2005 diking event took place, showed displacement as large as ~84mm/yr,
~53mm/yr, ~46mm/yr, ~17mm/yr, ~23mm/yr,~17mm/yr and ~6.36mm/yr towards the west direction
respectively. Sites DASM, GABH and DABB have a displacement towards the North East direction. The
site GABH, which is situated in Gabh’o volcano, shows rapid inflation from January to June (2006) and
continued with a slow uplifting till February 2007. Inflation began in June 2006 in the composite volcano
DABB site while subsidence that amount of about 16mm/yr is observed in Semera station called DASM.
Key words: Afar, Deformation, Inter-Dyking, InSAR, GPS, Rifting