Friday 12 August 2011

Earthquake in Mojen, northern Iran. 12 August 2011.

Just after 2 am local time on Friday the 12 August 2011 the Iranian town of Mojen, in Semnan to the southeast of the Caspian Sea, was shaken by a large earthquake. This was registered as a magnitude 5.0 on the Richter Scale at a depth of about 10 km, by the United States Geological Survey, and a magnitude 4.9 quake by the Institute of Geophysics at the University of Tehran. There are no reports of any damage or casualties, however Mojen is built on a steep hillside, from traditional mud-brick and wood materials, and a quake of this size would have caused considerable shaking at ground level, so it is likely that damage to buildings and injuries or even deaths may yet be reported.

Short video about Mojen.

Iran is one of the most earthquake-prone countries on earth. Iran, along with Afghanistan and western Pakistan, is part of a southern extension of the Eurasian Plate caught between the northeast moving Arabian Plate and the northwest moving Indian Plate. This has lead to the creation of a mountainous, earthquake-prone region called the Iranian Plateau. Although it is called a plateau it is not flat, just uplifted.

Relief map of the Iranian Plateau. Grey areas are highest, green lowest. Red dots indicate historic earthquakes, the red star the approximate position of the August 12 quake.

Despite Iran's oil wealth successive regimes have failed to invest in earthquake protection, resulting in a long history of devastating earthquake damage.

In 2003 an earthquake hit the city of Bam killing over 25 000 people, and injuring over 30 000 more, as well as destroying most of the city. This provoked a brief thaw in relations with the west as over 40 nations sent rescue teams into the area. Many of the casualties were caused by collapsing mud-brick buildings, which when shaken disintegrated so thoroughly as to exclude all air from the collapsed building, trapping and asphyxiating the sleeping victims; like the Mojen earthquake the Bam earthquake took place at about 2.oo in the morning. This similarity of building materials and timing raises concern for people caught in the Mojen earthquake.

The aftermath of the 2003 Bam Earthquake.

A similar earthquake in the northwest of the country in 1990 caused over 40 000 deaths and 60 000 injuries. This quake destroyed the cities of Rudbar, Manjil and Lushan, as well as over 700 villages, and left half a million people homeless. Again most of the fatalities were attributed to collapsing mud-brick buildings at night; this quake to place at 0.30 am.

The aftermath of the 1990 Manjil-Rudbar Earthquake.