The Algiers cluster is named for the capital city of Algeria, on the
southern coast of the Mediterranean Sea. It includes two M6 earthquakes,
both a short distance off-shore, Mw 6.0 on October 29, 1989 and Mw 6.7
on May 21, 2003. All events are observed to at least 6° epicentral
distance and most are observed teleseismically. The seismograph network
is very dense and well-placed to calibrate this cluster, but it reports
virtually no S arrivals. The P-arrivals are very good, however, and
provide a strong location calibration. All events have depth control,
mainly from near-source and local-distance readings, but many also have
constraint from teleseismic depth phases. The region is quite
seismically active and many more events could have been included in the
cluster. The ones chosen are generally the largest and best-recorded,
and provide a robust and representative sample of seismic observations
(except Sg and near-regional Sn) from the source region.
