The Ziarat cluster is named for the city of Ziarat in northeast
Baluchistan Province, Pakistan. The cluster includes 7.0 Ms and 7.4 Ms
earthquakes in August 1931 and the 7.1 Mw event on February 27, 1997.
The cluster is motivated by a pair of 6.4 Mw earthquakes that occurred
on October 28 and 29, 2008 and that provide a basis for location
calibration. The source region is very poorly instrumented but the 2008
sequence has been studied by several groups using InSAR to try to
unravel what is evidently a very complex faulting pattern, featuring as
many as 5 major faults with conjugate geometry. The location calibration
is done with indirect calibration, fitting the relative locations of the
mainshocks and larger aftershocks to this complex pattern. The InSAR
signal of a more recent Mw 6.0 event (October 6, 2021) helps in
constraining the calibration. Origin time is constrained by Pg and Sg
readings from the seismograph station QUE at Quetta, the only station
within local distance of the cluster. All earthquakes have depth
control, from near-source and local distance readings from QUE and for
many events, teleseismic depth phases. All events are observed at
teleseismic distances.
