1968 Dasht-e Bayaz and Ferdows earthquakes

1968 Dasht-e Bayaz and Ferdows earthquakes
	Tehran
UTC time	1968-08-31 10:47:43
ISC event	818488
USGS-ANSS	ComCat
Local date	August 31, 1968
Local time	14:17:43
Duration	1–2 minutes [1]
Magnitude	7.1 Mw[2]
Epicenter	34.02°N 58.96°E
Areas affected	Iran
Max. intensity	X (Extreme) [1]
Aftershocks	6.4 Mw Sept 1 at 07:27 [3]
Casualties	15,000 August 31 [4] ; 900 September 1 [4]

The Dasht-e Bayaz and Ferdows earthquakes occurred in Dashte Bayaz, Kakhk and Ferdows, Iran in late August and early September 1968. The mainshock measured 7.4 on the moment magnitude scale and had a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Damage was heavy in the affected areas with thousands of lives lost in the first event and many hundreds more in the second strong event.

Tectonic setting

The Iranian plateau is confined by the Turan platform in the north and the Zagros fold and thrust belt and Makran Trench in the south. The Arabian Plate is converging to the north with the Eurasian Plate at a rate of 35 millimeters (1.4 in) per year, and is diffused across a 1,000 km (620 mi) zone resulting in continental shortening and thickening throughout the plateau, with strike-slip and reverse faulting present, as well as subduction at the Makran coast.[5]

In eastern Iran, the shortening is accommodate by a combination of relatively short northwest–southeast trending reverse faults, long north–south trending right lateral strike-slip faults and shorter west–east trending left-lateral strike-slip faults.[2]

Earthquakes

USGS Shakemap for the August 31 event

The first earthquake occurred on August 31, 1968, measuring 7.1 on the moment magnitude scale. The focal mechanism indicated strike-slip faulting and the observed 80 km surface rupture showed that this earthquake resulted from movement on the western part of the west–east trending left-lateral Dasht-e-Bayaz Fault. The greatest observed left-lateral coseismic offset was about 4.5 m, with 2 m being the average observed offset.[2] The western end of the Dasht-e-Bayaz Fault ruptured and produced another large earthquake in 1979.[6]

Damage

The mainshock destroyed five villages in the Dasht-e Bayaz area, and at least half of the buildings in another six villages from Kakhk to Sarayan. A strong aftershock on September 1, measuring 6.4 on the moment magnitude scale, destroyed Ferdows. More than 175 villages were destroyed or damaged in this earthquake.

References

Niazi, M. (1969), "Source dynamics of the Dasht-e Bayāz earthquake of August 31, 1968", Bulletin of the Seismological Society of America, 59 (5): 1857, 1859, Bibcode:1969BuSSA..59.1843N, doi:10.1785/BSSA0590051843
Walker, R.; Jackson, J.; Baker, C. (2004). "Active faulting and seismicity of the Dasht-e-Bayaz region, eastern Iran". Geophysical Journal International. 157 (1): 265–282. Bibcode:2004GeoJI.157..265W. doi:10.1111/j.1365-2966.2004.02179.x.
Ambraseys, N. N.; Melville, C. P. (1982), A History of Persian Earthquakes, Cambridge Earth Science Series, Cambridge University Press, p. 165, ISBN 978-0521021876
Utsu, T. R. (2002), "A List of Deadly Earthquakes in the World: 1500–2000", International Handbook of Earthquake & Engineering Seismology, Part A, Volume 81A (First ed.), Academic Press, p. 707, ISBN 978-0124406520
Berberian, M.; Yeats, R. (1999), "Patterns of historical earthquake rupture in the Iranian Plateau", Bulletin of the Seismological Society of America, 89 (1): 120, Bibcode:1999BuSSA..89..120B, doi:10.1785/BSSA0890010120, archived from the original on January 10, 2012
R. T. Walker, E. A. Bergman, W. Szeliga, E. J. Fielding (2011). "Insights into the 1968-1997 Dasht-e-Bayaz and Zirkuh earthquake sequences, eastern Iran, from calibrated relocations, InSAR and high-resolution satellite imagery". Geophysical Journal International. 187 (3): 1577–1603. Bibcode:2011GeoJI.187.1577W. doi:10.1111/j.1365-246X.2011.05213.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links

Earthquakes with 1,000 or More Deaths since 1900 – United States Geological Survey
The International Seismological Centre has a bibliography and/or authoritative data for this event.

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[Niazi-1] Niazi, M. (1969), "Source dynamics of the Dasht-e Bayāz earthquake of August 31, 1968", Bulletin of the Seismological Society of America, 59 (5): 1857, 1859, Bibcode:1969BuSSA..59.1843N, doi:10.1785/BSSA0590051843

[Walker_etal_2004-2] Walker, R.; Jackson, J.; Baker, C. (2004). "Active faulting and seismicity of the Dasht-e-Bayaz region, eastern Iran". Geophysical Journal International. 157 (1): 265–282. Bibcode:2004GeoJI.157..265W. doi:10.1111/j.1365-2966.2004.02179.x.

[Ambraseys_p165-3] Ambraseys, N. N.; Melville, C. P. (1982), A History of Persian Earthquakes, Cambridge Earth Science Series, Cambridge University Press, p. 165, ISBN 978-0521021876

[Utsu-4] Utsu, T. R. (2002), "A List of Deadly Earthquakes in the World: 1500–2000", International Handbook of Earthquake & Engineering Seismology, Part A, Volume 81A (First ed.), Academic Press, p. 707, ISBN 978-0124406520

[5] Berberian, M.; Yeats, R. (1999), "Patterns of historical earthquake rupture in the Iranian Plateau", Bulletin of the Seismological Society of America, 89 (1): 120, Bibcode:1999BuSSA..89..120B, doi:10.1785/BSSA0890010120, archived from the original on January 10, 2012

[Walker-6] R. T. Walker, E. A. Bergman, W. Szeliga, E. J. Fielding (2011). "Insights into the 1968-1997 Dasht-e-Bayaz and Zirkuh earthquake sequences, eastern Iran, from calibrated relocations, InSAR and high-resolution satellite imagery". Geophysical Journal International. 187 (3): 1577–1603. Bibcode:2011GeoJI.187.1577W. doi:10.1111/j.1365-246X.2011.05213.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)