The Afar cluster is named for the Afar region of Ethiopia, Eritrea and
Djibouti. The cluster occupies the northern part of what has been termed
the Danakil or Arrata microplate. Much of the seismicity has occurred in
swarms associated with volcanic activity. The cluster includes five
events with magnitude greater than 6.0, in swarms that occurred in April
1969 and August 1989. All but five events in the cluster were recorded
at teleseismic distances. All events have depth control from near-source
and local-distance readings or (more frequently than usual) teleseismic
depth phases. Location calibration is based mainly on a seismic swarm
that was well-instrumented with a temporary network from November 2007
to February 2009, and included events large enough to be recorded at
teleseismic distances, which established the necessary connectivity with
events that lack local observations.
