Figure Captions:
Figure 1 . (a ) Seismotectonics of the study region.
Stars show the 2012 AVD hypocenter locations, and the related focal
mechanisms are by Momeni & Tatar, (2018). Faults are in lines. Vectors
are geodetic surface deformation rates by Masson et al., (2006), fixing
the central Iran block. Hexagons are historical earthquakes (Ambraseys
& Melvile, 1982; Berberian & Yeats, 1999, 2001). Circles are
instrumental earthquakes by Engdahl et al. (2006). Dashed ellipses show
affected regions by the 1593, 1721, 1780, and 1786 historical
earthquakes. Fault names are: ASF: Astaneh, WAF: West Alborz, SQF: South
Qoshadagh, GCF: Goshachay, NBF: North Bozkosh, SBF: South Bozkosh, NMF:
North Mishu, SMF: South Mishu, MGF: Maraghe, NKH: Nakhjavan, KHF:
Khajeh, and NHF: Nehram. NTF is in thick solid line. (b )
Circles: Seismicity recorded in IRSC network from 2006 until before the
AVD. Colors represent hypocentral depths. Faults are the same as (a).
Focal mechanisms with label are from the GCMT catalog until August 2020.
Those labeled M6.1 ARD, M6.5 AVD1, M6.3 AVD2, and M5.9 TKC are from the
1997 Ardebil, 2012 AVD doublet and 2019 Mw5.9 Torkamanchay earthquakes.
Triangles are the Tabriz permanent seismic sub-network stations belong
to IRSC.
Figure 2 . Seismicity along NTF and NMF. (a ): black
circles are the earthquakes from 2006 to before the 2012 AVD and white
circles are the earthquakes that occurred after 2012 AVD until 2019 TKC.
Ellipse is the estimated cumulative slip model for the creeping segment
of NTF near SND from 1721 AD historical earthquake until AVD. The dashed
circle is the thermal area (after Ghalamghash et al, 2019). (b )
up: histogram showing seismicity selected in distance of 5 km from NTF
and NMF shown in (a). NMF stands for North Mishu Fault. down: Diagram of
cumulative scalar seismic moments along NTF and NMF.
Figure 3 . Transferred Coulomb stress field from the
creeping segment of NTF on the (a ) AVD ruptures and
(b ) the Western and Eastern segments of the creep segment of
NTF, where high seismic activity was observed. The shown Coulomb stress
fields are for the depth of 6 km. Circles along NTF are earthquakes from
2006 until AVD. The rest are early aftershocks of the AVD (IRSC). Dashed
circle is the thermal area by Ghalamghash et al., (2019). Solid large
circle shows the area of neo-Sahand young craters near Bostan Abad (BA).
Dashed line marked A is the position of vertical cross sections shown in
Figures 5 and 6.
Figure 4 . (a ): Transferred Coulomb stress
fields from AVD ruptures on NTF (up: EV#1, down: EV#2). (b ):
Transferred Normal stress fields from AVD ruptures on NTF (up: EV#1,
down: EV#2). The shown stress fields are for the depth of 10 km.
Figure 5. Schematic plot illustrating the relation between SND
magmatic activity, NTF creeping segment, and AVD ruptures (marked AV#1
& AV#2). Low and high velocity areas are from Bavali et al., (2016),
Rezaeifar et al., (2016), and Ghalamghash et al, (2019) studies. Stars
are the 11 August 2012 M6.5&M6.3 mainshocks centroids. Thick dashed
line is the NTF. Horizontal dashed lines are crustal velocity layers
from Momeni & Tatar, (2018).
Figure 6. Graphic illustration of triggering of the 2012 AVD by
the transfer of Coulomb stress field produced by the central NTF
creeping segment. Stars are the mainshocks hypocenters. Rupture models
are from Momeni et al., (2019). Horizontal dashed lines are crustal
velocity layers from Momeni & Tatar, (2018).