T. Majidi Niri; H. Nazari; M. Ghorashi; M. Talebian; A. Kaveh Firooz
Abstract
Pishva fault with about 35km length is located between Alborz and Central Iran structural zones in southeast of Varamin. General trend of the fault is NW-SE (N38W, 33NE) which has reverse mechanism accompanied by sinistral component. Achieved Morphotectonic studies along the Pishva fault reveal its activity. ...
Read More
Pishva fault with about 35km length is located between Alborz and Central Iran structural zones in southeast of Varamin. General trend of the fault is NW-SE (N38W, 33NE) which has reverse mechanism accompanied by sinistral component. Achieved Morphotectonic studies along the Pishva fault reveal its activity. 3-5 seismic events with recurrence time of 3265 years are identified by studying on two Paleoseismic trenchs T1 and T2, The youngest and oldest events are 0.87 Ka and 29 Ka respectively. According to Wells and Coppersmith equations (1994), the biggest and smallest computed earthquake magnitudes are respectively 7.08 and 5.9. It would be possible to assign Shahr-e-Rey 1384 AD earthquake to this fault, since Event 1 is 870 years old.
Hamid Nazari; J-F Ritz; R Walker; R Salamati; A Ghasemi; A Shafei
Abstract
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 ...
Read More
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.