Bulletin of the Seismological Society of America, Vol. 89, No. 1, pp. 120-139, February 1999
Patterns of Historical Earthquake Rupture in the Iranian Plateau
by Manuel Berberian and Robert S. Yeats
"Destruction occurred within a radius of 12 farsangs [-72 km] from Tabriz city;
•.. very long fissures developed in most mountains, the fissures extended for approximately
7 farsangs [--42 kin] along the road to Shebli [located along the North
Tabriz active fault line]..." (Zonuzi, 1801 describing the 1780.01.08 Tabriz earthquake
of I o - IX +, Ms - 7.4 + ).
•.. very long fissures developed in most mountains, the fissures extended for approximately
7 farsangs [--42 kin] along the road to Shebli [located along the North
Tabriz active fault line]..." (Zonuzi, 1801 describing the 1780.01.08 Tabriz earthquake
of I o - IX +, Ms - 7.4 + ).
Abstract
The Iranian plateau accommodates the 35 mm/yr convergence rate between
the Eurasian and Arabian plates by strike-slip and reverse faults with relatively
low slip rates in a zone 1000 km across• Although these faults have only locally been
the subject of paleoseismological studies, a rich historical and archeological record
spans several thousand years, long enough to establish recurrence intervals of 1000
to 5000 yr on individual fault segments. Several clusters of earthquakes provide
evidence of interaction among reverse and strike-slip faults, probably due to adjacent
faults being loaded by individual earthquakes. The Dasht-e-Bayaz sequence of 1936
to 1997 includes earthquakes on left-lateral, right-lateral, and reverse faults. The
Neyshabur sequence of four earthquakes between 1209 and 1405 respected the segment
boundary between the Neyshabur and Binalud reverse fault systems. The two
pairs of earthquakes may have ruptured different faults in each segment, similar to
the 1971 and 1994 San Fernando, California, earthquakes. The 1978 Tabas reversefault
earthquake was preceded by the 1968 Ferdows earthquake, part of the Dashte-
Bayaz sequence. The North Tabriz fault system ruptured from southeast to northwest
in three earthquakes from 1721 to 1786; a previous cluster may have struck this
region in 855 to 958. The Mosha fault north of Tehran ruptured in three earthquakes
in 958, 1665, and 1830. Five large earthquakes struck the Tehran region from 743
to 1177, but only two that large have struck the area since 1177. Other earthquakes
occurred in pairs in the Talesh Mountains near the Caspian Sea (1863, 1896), the
Iran-Turkey border (1840, 1843), and the Nayband-Gowk fault system (both in
1981). Other historical events did not occur as parts of sequences•
The historic seismic moment release in Iran accounts for only a small part of the
plate convergence rate, which may be due to aseismic slip or to the Iranian historical
record, long as it is, being too short to sample long-term deformation across the
plateau. No historic earthquakes of M _--__ 8 have struck Iran. However, several long,
straight strike-slip faults (Doruneh, West Neh, East Neh, and Nayband) have not
sustained large historical earthquakes, raising the possibility that these long faults
could produce earthquakes of M = 8, thereby removing at least part of the apparent
slip deficit•
An increased understanding of Iran's seismic hazard could be obtained by an
extensive paleoseismology program and space-geodetic arrays, supplementing the
abundant historical and archaeological record.
the Eurasian and Arabian plates by strike-slip and reverse faults with relatively
low slip rates in a zone 1000 km across• Although these faults have only locally been
the subject of paleoseismological studies, a rich historical and archeological record
spans several thousand years, long enough to establish recurrence intervals of 1000
to 5000 yr on individual fault segments. Several clusters of earthquakes provide
evidence of interaction among reverse and strike-slip faults, probably due to adjacent
faults being loaded by individual earthquakes. The Dasht-e-Bayaz sequence of 1936
to 1997 includes earthquakes on left-lateral, right-lateral, and reverse faults. The
Neyshabur sequence of four earthquakes between 1209 and 1405 respected the segment
boundary between the Neyshabur and Binalud reverse fault systems. The two
pairs of earthquakes may have ruptured different faults in each segment, similar to
the 1971 and 1994 San Fernando, California, earthquakes. The 1978 Tabas reversefault
earthquake was preceded by the 1968 Ferdows earthquake, part of the Dashte-
Bayaz sequence. The North Tabriz fault system ruptured from southeast to northwest
in three earthquakes from 1721 to 1786; a previous cluster may have struck this
region in 855 to 958. The Mosha fault north of Tehran ruptured in three earthquakes
in 958, 1665, and 1830. Five large earthquakes struck the Tehran region from 743
to 1177, but only two that large have struck the area since 1177. Other earthquakes
occurred in pairs in the Talesh Mountains near the Caspian Sea (1863, 1896), the
Iran-Turkey border (1840, 1843), and the Nayband-Gowk fault system (both in
1981). Other historical events did not occur as parts of sequences•
The historic seismic moment release in Iran accounts for only a small part of the
plate convergence rate, which may be due to aseismic slip or to the Iranian historical
record, long as it is, being too short to sample long-term deformation across the
plateau. No historic earthquakes of M _--__ 8 have struck Iran. However, several long,
straight strike-slip faults (Doruneh, West Neh, East Neh, and Nayband) have not
sustained large historical earthquakes, raising the possibility that these long faults
could produce earthquakes of M = 8, thereby removing at least part of the apparent
slip deficit•
An increased understanding of Iran's seismic hazard could be obtained by an
extensive paleoseismology program and space-geodetic arrays, supplementing the
abundant historical and archaeological record.
Tabriz
"The Sorkhab Mountain [in north Tabriz] was faulted
by deep fissures of 2 zars [-2 meters] wide and 2 farsangs
[-12 kin] long trending southeast [along the
North Tabriz fault]..." (Donboli, 1813 A.D., describing
the 1780 Tabriz earthquake).
The Tabriz region is located in the Araxes structural
block of northwestern Iran, southwest of the continuation of
the western Alborz Mountains toward the Caucasus. The
North Tabriz fault (NTF) is a complex northwest-trending
structure that contains evidence of right-lateral strike-slip
displacement observed on aerial photographs, and vertical
displacement with the north side up (Fig. 7; Berberian and
Arshadi, 1976; Berberian, 1997; Berberian and Qorashi,
1987, 1999b). The NTF merges northwest with a zone of
reverse faults that turns to the west-southwest in the area
north of Lake Urumiyeh (Sufian and Tasuj faults; Fig. 7),
and it merges southeast with another zone of reverse faults,
which turns to the east-northeast (South and North Bozqush,
Duzduzan, and South Sarab faults; Fig. 8).
The NTF system and adjacent reverse faults ruptured
from southeast to northwest in three earthquakes in 65 yr:
the Shebli earthquake (M - 7.3) in 1721 on the southeastern
NTF with a surface rupture >35 km long as reported by
Brydges (1834); the Tabriz earthquake (M -- 7.4) in 1780
on the northwestern NTF, with surface rupture >42 km long
and 2- to 4-m vertical separation as reported by al-Omari
(1795), Zonuzi (1801), Donboli (1813), and Drouville
(1825); and the Marand-Mishu earthquake (M -- 6.3) in
1786 on the Mishu reverse fault and the Sufian segment of
the NTF. A fourth earthquake of M -- 5.5 struck the Tasuj
reverse fault farther west in 1807. A fifth earthquake of M
6.7 took place along the South Bozqush reverse fault farther
southeast in 1879 (Fig. 8; see discussion later). The
earthquake segment boundaries correspond to geometric discontinuities
such as stepovers (overlaps, offsets) and abrupt
changes in strike. The boundary between the Tabriz and
"The Sorkhab Mountain [in north Tabriz] was faulted
by deep fissures of 2 zars [-2 meters] wide and 2 farsangs
[-12 kin] long trending southeast [along the
North Tabriz fault]..." (Donboli, 1813 A.D., describing
the 1780 Tabriz earthquake).
The Tabriz region is located in the Araxes structural
block of northwestern Iran, southwest of the continuation of
the western Alborz Mountains toward the Caucasus. The
North Tabriz fault (NTF) is a complex northwest-trending
structure that contains evidence of right-lateral strike-slip
displacement observed on aerial photographs, and vertical
displacement with the north side up (Fig. 7; Berberian and
Arshadi, 1976; Berberian, 1997; Berberian and Qorashi,
1987, 1999b). The NTF merges northwest with a zone of
reverse faults that turns to the west-southwest in the area
north of Lake Urumiyeh (Sufian and Tasuj faults; Fig. 7),
and it merges southeast with another zone of reverse faults,
which turns to the east-northeast (South and North Bozqush,
Duzduzan, and South Sarab faults; Fig. 8).
The NTF system and adjacent reverse faults ruptured
from southeast to northwest in three earthquakes in 65 yr:
the Shebli earthquake (M - 7.3) in 1721 on the southeastern
NTF with a surface rupture >35 km long as reported by
Brydges (1834); the Tabriz earthquake (M -- 7.4) in 1780
on the northwestern NTF, with surface rupture >42 km long
and 2- to 4-m vertical separation as reported by al-Omari
(1795), Zonuzi (1801), Donboli (1813), and Drouville
(1825); and the Marand-Mishu earthquake (M -- 6.3) in
1786 on the Mishu reverse fault and the Sufian segment of
the NTF. A fourth earthquake of M -- 5.5 struck the Tasuj
reverse fault farther west in 1807. A fifth earthquake of M
6.7 took place along the South Bozqush reverse fault farther
southeast in 1879 (Fig. 8; see discussion later). The
earthquake segment boundaries correspond to geometric discontinuities
such as stepovers (overlaps, offsets) and abrupt
changes in strike. The boundary between the Tabriz and
Marand-Mishu earthquakes corresponds to the boundary between
the NTF and the Mishu fault (Fig. 7).
The Tabriz-Dehkharqan earthquake (M -- 6.8) in 1641
(Melville, 1981) was south of the boundary between the
Shebli and Tabriz earthquake. The earthquake was witnessed
and documented by the Armenian celibate priest Arakel Vartabed
Tavrizetsi (1670) and also by Mohammad Nassir
(1641), who was assigned by the government to evaluate the
damage and death toll. The northeast-trending meizoseismal
zone of the earthquake does not correspond to any mapped
fault. The southeastern continuation of the NTF has had historical
earthquakes only smaller than M 6, which is also the
case for the northwestern continuation of the Mishu-Sufian
reverse faults
Prior to the 1721 to 1786 earthquake sequence, Tabriz
was struck by earthquakes in 858 (M - 6.0), 1042 (M
7.3; with ground fracture witnessed by Qatran Tabrizi,
1042), 1273 (M ~ 6.5; witnessed by Bar-Hebraeus, 1286),
and 1304 (M - 6.7; Fig. 8). However, the meizoseismal
zones of these older earthquakes are not known well enough
to speculate on which faults were responsible for them. The
1273 and 1304 earthquakes are a temporal cluster like the
1721 to 1786 events, but the direction of propagation is not
known (Berberian, 1997).
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