SSD of GSI preliminary report number: 17-01, ver.01

shahryar.solaymani@gmail.com

Preliminary report on geological features of the Ezgaleh-Kermanshah earthquake

(M~7.3), November 12, 2017, West Iran

Dr. Shahryar SOLAYMANI AZAD, N. Saboor, M. Moradi, A. Ajhdari, T. Youssefi, Dr. M. Mashal, Dr. M. Roustaie

At 21:48' (local time), on November 12, 2017, a strong quake of magnitude 7.3 struck

the region west of Kermanshah city (within Zagros structural domain), in western Iran.

The death toll in this event has risen to at least 400. The powerful earthquake caused

vast destruction in the region given the number of cities and villages located within

the affected area. Refer to historical earthquake catalogue (e.g. Ambraseys and

Melville, 1982), the area had been subjected at least to two moderate-strong

earthquakes in 958 and 1150 AD.

Fig. 1 The recent seismotectonic map of Iran, presented by the Seismotectonics and Seismology

Department of Geological Survey of Iran (Oveisi et al. 2017) and the domain of West Kermanshah-

Ezghaleh earthquake (black rectangle; Fig. 2).

Fig. 2 The domain of West Kermanshah-Ezgaleh earthquake presented in the seismotectonic map of

the area. Epicenter from IIEES.

InSar imagery and interferometry analysis and active tectonic field studies have been

undertaken to assess the causative fault and the probable co-seismic surface faulting.

All the first and secondary orders co-seismic geological features (e.g. seismogenic

cracks, dynamic rockfalls, major triggered landslides, stone jumping, etc.) have been

studied to assess the meizoseismal area of the quake and its causative fault zone. In

general view, the Zagros structural domain is located in the central portion of the

Arabia-Eurasia young collision zone (e.g. Berberian, 1995; Agard et al., 2005; Oveisi

et al., 2009). The affected zone of this strong seismic event contains the MFF

(Mountain Front Fault) and HZF (High Zagros Fault) of main Zagros structures.

Within the study area, these two active fault zones are located closer to each other in

the NW. In Zagros structural domain, the MFF is a basement thrust fault (dipping NE)

and the HZF is a reverse fault with a small dextral component (dipping NE).

Fig. 3 Vast surface deformation zone of the West Kermanshah-Ezgaleh earthquake on interferometry

maps and section.

Fig. 4 Huge landslide-rock avalanche triggered by the strong earthquake of West Kermanshah- Ezgaleh

within the meizoseismal zone, near Palan Sofla village (looking south).

Fig. 5 Rockfall triggered by the strong earthquake of West Kermanshah- Ezgaleh within the

meizoseismal zone, near Marshayer village (looking east). The large boulder (in the left side) has been

displaced about 200 meters.

Fig. 6 Scars of the impacted boulder shown in Fig. 4 (about 25m3 in volume & 60 tonnes in weight),

within the meizoseismal zone of the seismic event, near Marshayer village. Note to decreasing in the

jumping distance and the depth of impact scars of the boulder.

Fig. 7 Landslide failures which formed by West Kermanshah-Ezgaleh strong seismic event, near

Cham-Zereshk village (looking south).

Fig. 8 Stone jumping caused in the meizoseismal area of the earthquake, near Bezmirabad village.

Fig. 9 Water and sand boiling occurred within the meizoseismal area of the West Kermanshah-Ezgaleh

earthquake, near Palan Olia village (looking north).

The assessment was mainly focused on the Sarpol-e Zahab region and Ezgaleh city

due to the extent of destruction and that being relatively close to the source of the

earthquake (MFF and HFZ). Our preliminary assessment highlights the concentration

of the secondary order co-seismic geological features on the hanging wall of the MFF,

close to the HZF zone. In general view, most of the Zagros active thrust faults play a

role as blind faults (e.g. Berberian, 1995). However, taking into account the

magnitude of the earthquake occurred at a shallow depth, there could be a possibility

of forming a co-seismic surface faulting. The recent studies (e.g. Oveisi et al., 2009;

Palizvan, 2016; Motaghi et al., 2017; Solaymani Azad et al., 2017) reveal the

detachment depth of 15-18 km in the basement within this sector of the Zagros

domain. This is more or less in agreement with the focal depth of the recent

earthquake. Hence, it is possible for the quake not to be accompanied by surface

faulting.

Fig. 10 The epicentral domain of the West Kermanshah-Ezgaleh strong earthquake located on the

hanging wall of the MFF, within Zagros domain. Accordingly, it is possible for the quake not to be

accompanied by surface faulting. Epicenter from IIEES.

Fig. 11 The hypo & epicentral zones of the West Kermanshah-Ezgaleh strong earthquake located on

the hanging wall of the MFF, within Zagros domain. The recent studies (e.g. Oveisi et al., 2009;

Motaghi et al., 2017) reveal the detachment depth of 15-18 km in the basement within this sector of the

Zagros domain. This more or less is in agreement with the focal depth of the earthquake.

References:

Agard, P., Omrani, J., Jolivet, L., Mouthereau, F., 2005. Convergence history across the

Zagros (Iran): constraints from collisional and earlier deformation. Int. J. Earth Sci. 94, 409–

419.

Ambraseys, N.N., Melville, C.P., 1982. A History of Persian Earthquakes. Cambridge

University Press, New York.

Berberian, M., 1995. Master “blind” thrust faults hidden under the Zagros folds: active

basement tectonics and surface morphotectonics. Tectonophysics 241, 193–224.

Geological map of Qasr-e Shirin (Scale 1:250,000), 1963, The British Petroleum Company.

Oveisi, B., Lave, J, Van Der Beek, P., Carcaillet, J., Benedetti, L and Aubourg, Ch ,2009,

Thick and thin-skinned deformation rates in the central Zagros simple folded zone (Iran)

indicated by displacement of geomorphic surfaces, Geophysical Journal International, VOL

176, Issue 2, page 627-654.

Motaghi, K., Shabanian, E., Kalvandi, F, 2017, Underplating along the northern portion of the

Zagros suture zone, Iran, Geophysical Journal International 210 (1), 375-389

Palizvan, 2016, Mechanism of Quaternary faulting in west of Kermanshah and the

relationship with local seismicity. Master's thesis. Institute for Advanced Studies in Basic

Sciences, Gava Zang, Zanjan, Iran, (in Persian).

Solaymani Azad, S., Saboor, N., Moradi, M., Ajhdari, A., Youssefi, T., Mashal, M., Roustaie,

M., 2017, Preliminary report on geological investigations of the Ezgaleh-Kermanshah

earthquake (M~7.3), November 12 2017, West Iran, Website report of the Geological Survey

of Iran, (in Persian).

Acknowledgments: We are grateful to Dr. Esmail Shabanian, Dr. Mohammad Foroutan, Dr. Behnam

Oveisi and Rambod Amigh for their insightful comments and discussions.