1958 Firuzabad earthquake
   Tehran | |
| UTC time | 1958-08-16 19:13:48 |
|---|---|
| ISC event | 884953 |
| USGS-ANSS | ComCat |
| Local date | 16 August 1958 |
| Local time | 22:43:48 |
| Magnitude | 6.7 Mw[1] |
| Depth | 15 km (9 mi)[1] |
| Epicenter | 34°17′24″N 47°52′01″E / 34.290°N 47.867°E[1] |
| Areas affected | Iran |
| Max. intensity | MMI IX (Violent) |
| Foreshocks | Yes |
| Aftershocks | Yes |
| Casualties | 132 killed, 948 injured[2] |
The 1958 Firuzabad earthquake was the second destructive earthquake to strike Hamadan province, Iran, in nine months. The Mw 6.7 earthquake occurred at a depth of 15 km (9.3 mi) on 16 August at 22:43 local time. It caused severe damage to over 170 villages in the province. Due to several strong foreshocks, most of the population fled their homes and the death toll only stood at 132 and another 948 were injured. A destructive aftershock on 21 September killed another 16 people.
Tectonic setting
[edit]
The Zagros Mountains stretching from Turkey to the Gulf of Oman, through Iran and Iraq for 1,500 km (930 mi) formed from continental collision involving the Arabian plate and Central Iran. Its formation occurred during the late-Triassic, late-Jurassic, late-Cretaceous, Oligocene and Pliocene. During its early formation, some extensional tectonics may have occurred. The mountain range is still accommodating deformation, evident from present-day seismicity. Deformation is accommodated by thrust and strike-slip faulting within the range. Parallel to major thrust faults of the mountains is the Main Recent Fault, an active right-lateral strike-slip fault.[3] Convergence between the Arabian plate and Iran occurs obliquely along the Zagros Mountains, and approximately 30–50 percent of the ~25 cm (9.8 in) per year convergence between the two plates is accommodated along the range.[4]
The Main Recent Fault delineates the northeastern boundary of the seismically active Zagros Mountains, forming between 3 and 5 million years ago. It runs parallel to the Main Zagros Reverse Fault, a suture zone separating the Sanandaj-Sirjan Zone from the fold and thrust belt. The fault comprises several segments with lengths of more than 100 km (62 mi). Southwest of the Main Recent Fault lies the continental margin of Arabia while the rocks to the northeast are of metamorphic and volcanic origin. Its southeastern segments ends in a zone of north–northwest trending strike-slip faults. The strike-slip component of this oblique convergence is accommodated along the Main Recent Fault. The southeastern segments are more seismically active in contrast to the northwestern segments.[5]
Earthquake
[edit]Foreshocks and aftershocks
[edit]Aftershock activity associated with the 13 December 1957 Farsinaj earthquake continued until mid-February 1958. On 14 August, at 14:00 local time, earthquake activity resumed with a magnitude 5.7 event that was felt strongly in Asadabad, Nahavand and Tuyserkan and scared residents. A magnitude 5.5 earthquake occurred at 19:30; described as violent, it damaged several nearby villages around the three aforementioned cities. These foreshocks had their own sequences of aftershocks with the largest measuring 4.7 and the mainshock on 16 August was preceded by a magnitude 4.5 shock two hours prior. These earthquakes caused panic among the populations and some were damaging. Tourists of Hamadan fled the city following these foreshocks. The last felt foreshock also caused minor damage to villages.[6]: 2–6
The mainshock was followed by three large aftershocks exceeding magnitude 5.0 while another 30 had magnitudes between 4.0 and 4.9. On 17 August an aftershock damaged several homes in Kangavar and two more in Karkhaneh. Several people died in Asadabad and Akbarabad when homes crumbled during an aftershock in the early morning of 19 August. The most destructive aftershock occurred in Dinavar District on 21 September, devastating a 100 km2 (39 sq mi) region northwest of the 1957 meizoseismal area. Preceded by a damaging sequence of earthquakes several hours earlier, this magnitude 5.2 shock killed 16 people and devastated Karkasar, Karaj, Balajub, Gamshah, and Kolehjub. Fifty-seven injuries were reported in the villages of Karkasar and Karaj. Homes in Karaj sustained damage including fractured walls and one home was destroyed in the prior earthquake sequence.[6]: 16
Mainshock
[edit]The mainshock and its aftershocks occurred southeast of the 1957 earthquake epicenter. Both earthquakes occurred along different segments of the Main Recent Fault. Three sets of surface rupture occurred; all trending northwest–southeast on segments of the Main Recent Fault exhibited vertical offsets. One of these ran 15 km (9.3 mi) between Givaki and Cheshmeh Mahi produced up to 2 m (6 ft 7 in) of vertical offset. The rupture extended across the Garrin segment to the southeast and Sahneh segment to the northwest. The Nahavand segment was associated with another 20 km (12 mi) surface rupture that extended form Barreh Farakh to Laylan. The third surface rupture zone ran for 8 km (5.0 mi) and coincided with the southeastern part of the Sahneh segment.[7]
The earthquake was felt for 180,000 km2 (69,000 sq mi); a significantly larger extent in comparison with the 1957 shock. Modified Mercalli intensity VII (Very strong) was assigned to the meizoseismal area although there were plausibly isolated instances of IX (Violent) effects. It was impossible to further assess the damaged adobe buildings as these structures do not remain intact beyond intensity VII. Some infrastructure in the meizoseismal zone had been damaged by the 1957 shock and its aftershock which could not be distinguished from actual damage caused by the 1958 earthquake.[6]: 18, 20
Damage and casualties
[edit]The mainshock killed at least 132 people, injured hundreds and killed 3,000 livestock. Approximately 2,500 homes across 170 villages were levelled, rendering 10,000 homeless. The low death toll was partly the result of a foreshock that kept residents alert and the hot weather that motivated people to rest on their roofs.[6]: 6, 9–13
The earthquake devastated the Khezel, Solgi and Deh Now-e Sofla districts. The meizoseismal area encompassed a 1,100 km2 (420 sq mi) area along the Gamasiab River, and damage was greatest in the northwest. Four settlements, Leylas-Leylan, Jafarabad and Litagar, situated in the northwest meizoseismal zone, experienced the greatest devastation. Located some 10 km (6.2 mi) from Deh-e Bozorg-e Firuzabad, these villages were also affected by the 1957 earthquake and its aftershocks. There, all homes were razed, and in Leylas, cows were knocked off their feet and residents had difficulty maintaining their balance. About 200 died or were injured in these villages.[6]: 6, 9–13
The village of Rudbari was damaged by landslides and slumps. All homes were flattened in Hoseynabad and Sharifabad; the latter settlement reported heavy livestock loss and 16 injuries. In Firuzabad, two people died from toppled adobe walls; several damaged homes were restored after the 1957 shock. The village of Dehkuhneh was in the process of reuilding after the 1957 shock when it was completely devastated again; there were two deaths and 23 injuries. Slumping of the riverbank near Deh-e Bozorg-e Firuzabad damaged a bridge while the village experienced widespread damage and collapses. The shaking at Asadabad, persisted for a while and many people could not walk properly. One home also collapsed in the city and buried a person. Three people died and nine were injured in the flattened town of Barfaragh.[6]: 6, 9–13
See also
[edit]References
[edit]- ^ a b c ISC (27 June 2022), ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009), Version 9.1, International Seismological Centre, archived from the original on 25 November 2016, retrieved 5 December 2022
- ^ National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K, retrieved 2022-12-05
- ^ Tchalenko, J. S.; Braud, J. (1974). "Seismicity and structure of the Zagros (Iran): the Main Recent Fault between 33 and 35° N". Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences. 277 (1262): 1–25. doi:10.1098/rsta.1974.0044. S2CID 122302270.
- ^ Yamini-Fard, F.; Hatzfeld, D.; Tatar, M.; Mokhtari, M. (2006). "Microearthquake seismicity at the intersection between the Kazerun fault and the Main Recent Fault (Zagros, Iran)". Geophysical Journal International. 166 (1): 186–196. Bibcode:2006GeoJI.166..186Y. doi:10.1111/j.1365-246X.2006.02891.x. S2CID 130787307.
- ^ Rahimzadeh, Bahman; Bahrami, Shahram; Mohajjel, Mohammad; Mahmoudi, Hossein; Haj-Azizi, Farzad (2019). "Active strike-slip faulting in the Zagros Mountains: Geological and geomorphological evidence of the pull-apart Zaribar Lake basin, Zagros, NW Iran". Journal of Asian Earth Sciences. 174: 332–345. Bibcode:2019JAESc.174..332R. doi:10.1016/j.jseaes.2018.12.017.
- ^ a b c d e f Ambraseys, N.N.; Moinfar, A.A. (1974). "The seismicity of Iran. The Firuzabad (Nehavend) earthquake of 16 August 1958". Annals of Geophysics. 27 (1–2): 1–21. doi:10.4401/ag-4910.
- ^ {Berberian, Manuel (2014). "12: 1900–1963 Coseismic Surface Faulting". Developments in Earth Surface Processes] Earthquakes and Coseismic Surface Faulting on the Iranian Plateau – A Historical, Social and Physical Approach. Vol. 17. pp. 278–280. doi:10.1016/B978-0-444-63292-0.00012-0. ISBN 978-0-444-63292-0.