TY - JOUR
T1 - New evidence for Afro-Arabian plate separation in southern Afar
AU - Ayele, Atalay
AU - Nyblade, Andrew A.
AU - Langston, Charles A.
AU - Cara, Michel
AU - Leveque, Jean J.
PY - 2006
Y1 - 2006
N2 - The May 2000 earthquake cluster, around 10° N and 41° E in southern Afar, has been studied using high quality data from 12 temporary and permanent broadband seismic stations deployed in the area. 140 earthquakes have been located using P- and S-wave arrival times, a well-constrained velocity model, and a double-difference location algorithm. Source mechanisms and moment magnitudes for the four largest events (M > 4) have been obtained from moment tensor inversion. There is no clear alignment of the epicentres along a fault zone; however, the events are clustered slightly southeast of Mount Amoissa along WNW-ESE extension of the Ayelu-Amoissa (Abida/Dabita) lineament. Focal mechanisms show fault motion along WNW-ESE to east-west striking normal faults, with extension oblique to the orientation of the Main Ethiopian Rift. The non-double-couple components of the source mechanisms range from 18-25%, suggesting that the seismic activity is of tectonic origin and not volcanic. Source depths are ≤7 km, in good agreement with estimates of the elastic thickness of the Afar lithosphere. We suggest that the Gewane earthquake swarm represents remnant strain accommodation along a previous line of weakness in southern Afar related to the separation of Arabia from Africa because the focal mechanisms show north-south extension similar to many of the events in central Afar at the triple junction where Arabia is presently rifting away from Africa.
AB - The May 2000 earthquake cluster, around 10° N and 41° E in southern Afar, has been studied using high quality data from 12 temporary and permanent broadband seismic stations deployed in the area. 140 earthquakes have been located using P- and S-wave arrival times, a well-constrained velocity model, and a double-difference location algorithm. Source mechanisms and moment magnitudes for the four largest events (M > 4) have been obtained from moment tensor inversion. There is no clear alignment of the epicentres along a fault zone; however, the events are clustered slightly southeast of Mount Amoissa along WNW-ESE extension of the Ayelu-Amoissa (Abida/Dabita) lineament. Focal mechanisms show fault motion along WNW-ESE to east-west striking normal faults, with extension oblique to the orientation of the Main Ethiopian Rift. The non-double-couple components of the source mechanisms range from 18-25%, suggesting that the seismic activity is of tectonic origin and not volcanic. Source depths are ≤7 km, in good agreement with estimates of the elastic thickness of the Afar lithosphere. We suggest that the Gewane earthquake swarm represents remnant strain accommodation along a previous line of weakness in southern Afar related to the separation of Arabia from Africa because the focal mechanisms show north-south extension similar to many of the events in central Afar at the triple junction where Arabia is presently rifting away from Africa.
UR - http://www.scopus.com/inward/record.url?scp=33745804340&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33745804340&partnerID=8YFLogxK
U2 - 10.1144/GSL.SP.2006.259.01.12
DO - 10.1144/GSL.SP.2006.259.01.12
M3 - Article
AN - SCOPUS:33745804340
SN - 0305-8719
VL - 259
SP - 133
EP - 141
JO - Geological Society Special Publication
JF - Geological Society Special Publication
ER -