The Kunar cluster is named for Kunar Province in the lower Hindu Kush
Mountains of eastern Afghanistan. The cluster is based on a devastating
6.0 Mw earthquake on August 31, 2025, and includes a 6.2 Mw earthquake
on February 1, 1984. Location calibration of this cluster is done with
the indirect method, taking advantage of InSAR models produced for the
mainshock and a 5.5 Mw aftershock on September 4. These models indicated
that the rupture was quite shallow, less than 10 km, a finding confirmed
by detailed waveform studies of the mainshock and largest aftershock.
The calibration shift for epicenters is 10.7 km at an azimuth of 250°.
Calibration of the origin time of the cluster is based on observations
of Pg and Sg arrivals at stations to the west (KBL and KBU) and east
(mainly CEP) of the cluster at distances of 0.5° to 1.5° epicentral
distance. The crustal velocity model was found to require a crustal
thickness of ~60 km, so direct-arriving crustal phases can be observed
at greater distances than usual. Resolution of the depth and origin time
calibration for this cluster is weaker than usual because of the
scarcity of seismological data. Resolution of relative locations is
improved for some events by the use of differential time measurements
provided by Will Yeck (NEIC). All events have depth control, mainly from
local distance arrivals.
