Buin Zahra Earthquake of 1 September 1962, Ms=7.2
This large-magnitude earthquake destroyed 91 villages, killing 12,225 and seriously injuring 2800 people (fatalities represented 11.6% of the total population of 142,029 in the epicentral area of 5387 km2) in the area south of the city of Qazvin. Over 21,300 houses in 300 villages were damaged beyond repair or partially destroyed, 180 of them with loss of life. The earthquake was associated with surface ruptures of unknown length along the Ipak fault with left-lateral, oblique-reverse displacements. Bedding-plane slips with a thrust mechanism (flexural-slip faulting), landslides, and reactivation of old thrusts or beddings (in the Eocene volcanic, Cretaceous carbonate rocks, or between the Cretaceous carbonates and the Eocene volcanics; due to gravity in Chenar, Kuh-e Miyanband, and Rostamabad) were misreported as coseismic surface ruptures by almost all the authors in the early 1960s. Discontinuous ruptures deduced from a few and widely spaced observations with unconfirmed total length of 55–103 (?) km, with vertical displacements of 40–76 cm, accompanied by left-lateral horizontal slip of 15–50 cm were reported by different authors. Bearing in mind that the western and central sections of the surface rupture were not visited; the highest displacements were recorded along the eastern segment of the coseismic surface rupture during the widely spaced observation traverses. The earthquake was also associated with intense bedding-plane slip with a thrust mechanism in the heavily fissured area (6 km long*2 km wide) of the Rudak-Tufak area in the Neogene and Pliocene molasse deposits, which was not identified by the original investigators. This indicated flexuralslip folding above the blind Tufak thrust to the north of the Ipak fault.