Fault Rupture in the Iranian (Dasht-e-bayāz) Earthquake of August 1968

Abstract

A FIELD study after the destructive Iranian earthquake sequence beginning at 10 ^h 27 ^m GMT on August 31, 1968, has brought to light a major fault rupture. The precise extent and nature of the rupture are important to theories of earthquake mechanism. The main shock, which had a magnitude of 7.7 (estimated at Berkeley), caused severe damage over 20,000 km² and was felt over twenty times this area, in the Khorassan province of Iran. Towns and villages which suffered heavily were Dasht-e-bayāz, Kakhk, Khezri, Miam, Beynavāch, Boskabad, Charmeh and Ferdows (Fig. 1). Kakhk, with a population of more than 7,000, alone accounted for one-third of the estimated 12,000 to 14,000 killed. Damage was, however, more complete in the village of Dasht-e-bayāz, where all buildings (including a mosque, estimated to be 800 yr old) were levelled and about 85 per cent of the population of 2,400 were killed. Earthquakes have struck the area before and people are familiar with the sensation caused by the ground shaking at the time of weaker earthquakes. The most recent earthquake still remembered by many is that of September 23, 1947, which destroyed Doulatabad, about 25 km south-east of Sarayān (Fig. 1), and left more than 400 dead.