Document Type : Original Research Paper


1 Research institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran. Laboratoire Géosciences Montpellier, Université Montpellier, France.

2 Laboratoire Géosciences Montpellier, Université Montpellier, France

3 COMET, Department of Earth Sciences, University of Oxford, Oxford, UK

4 Geological Survey of Iran, Tehran, Iran


The Firouzkuh Fault in most of its extension is located at the southern side of Firouzkuh Valley in west of the Central Alborz.  It is a SW – NE prominent structure with a 70 km long on a sinistral –normal fault. It has been known as a south-dipping reverse fault.Paleoseismic analysis and C14 dating along the Firouzkuh left -lateral strike-slip fault indicate that Central Alborz has been shaken by large earthquakes during the Holocene. Here we present the data carried out of one of the two excavated trenches with 15 m long, 2m wide, ~ 4m deep in the east of Firouzkuh, where we found some evidence for last paleoearthquake associated to seismic re-activity  on Firouzkuh Fault in the second trench (F2) that dug across a gauge zone. The last event is evidenced by cutting young superficial deposit where this faulted unit stratigrafically covered alluvium deposits yielded dated human bones fragments. The bones found in 60-70cm-deep of trench which a C14 age of 1159 ± 28 BP. Regarding to estimated slips per event on paleoseismological log of eastern wall of trench F1, event magnitudes for each paleoearthquakes are M≈7.


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