The Spitak cluster was formed around the M6.0 December 7, 1988, earthquake near Spitak, Armenia but it includes earthquakes into southern Georgia. It was built around a subset of mostly small events that have good local coverage to constrain focal depths and velocity structure. These were relocated with free depth. Larger events were added to provide coverage at regional and teleseismic distances. It is often difficult to include older events in calibrated clusters because of connectivity problems but many of the seismic stations in this region have operated for a long time and this cluster includes a 1961 event (as well as several other events from the 1960s and '70s) that locates close to the eventual source region in the 1988 sequence.
Number of events: 62
Calibration type: direct calibration using data to 0.6 degrees; hypocentroid calibration level = 0.9 km
Epicentral calibration range: 1 - 3 km
Date range: 19611203 - 20160721
Latitude range: 40.763 - 41.593
Longitude range: 43.458 - 44.463
Depth range: 5.0 - 22.8
Magnitude range: 2.4 - 6.0
