Magnitude 7.7 Earthquake in Balochistan; over 350 dead and new island created.

The United States Geological Survey recorded a Magnitude 7.7 Earthquake at a depth of 15 km in Baluchistan Province in southeast Pakistan, slightly before 4.30 pm local time (slightly before 11.20 am GMT) on Tuesday 24 September 2013. This is an extremely large and dangerous Earthquake, and was felt as far away as New Delhi and Dubai. Over 350 casualties have been recorded already, a number which is likely to rise sharply, and buildings have been destroyed across Arawan District, where the quake occurred. Villages close to the epicenter are said to have had around 90% of homes destroyed; building collapses are a particular danger in Baluchistan as many buildings are made of mud bricks, which can liquify in Earthquakes forming a fine dust which asphyxiates people trapped beneath fallen structures. There have been a number of aftershocks in the area, several of which have been Earthquakes in excess of Magnitude 5.

Villagers in Labach in Arawan District forced to sleep outside following the destruction of their homes by the 24 September 2013 Earthquake. Arshad Butt/AP.

The quake also lead to the formation of a new island off the coast of Gwadar, roughly 400 km to the southwest of the event's epicenter. This is roughly 18 m high and covers an area of approximately 30 by 76 m. Earthquakes on thrust belts can form hills and islands by forcing rock formations up over other rocks (this is how most mountains are formed, though not by single events), but on this occasion the new island is thought to be the result of a mud volcano, according to geologists from the Pakistan Navy. Mud volcanoes are not true volcanoes (caused by hot magma from deep within the Earth) but are the result of liquids or gasses being released suddenly from rocks into soft sediments, resulting in dramatic upwelling of mud and gas. In this gas the new island has been found to be venting methane in a number of places, leading to the conclusion that a sudden change of pressure caused methane ice buried in the mud to thaw, causing it to expand rapidly and raise sediment to form the new island. Frozen methane in marine sediments is quite common, as the gas freezes at quite high temperatures under pressure. Mud volcanoes are a fairly common occurrence in Baluchistan, though where they occur offshore, as is the case with this one, they are often eroded away by the sea fairly quickly.

Residents of Gwadar investigating the new island on 25 September 2013. Behram Balochi/AFP/Getty Images.

The quake occurred directly on the Makran Fault, along which the Arabian Plate to the south is being subducted beneath the Eurasian Plate to the north. The Arabian Plate is being pushed northward by the movement of the African Plate to the south, as well as expansion beneath the Red Sea caused by the formation of new oceanic crust. To the west the continental portion of the Arabian Plate is in contact with the Eurasian Plate, causing folding and uplift that is leading to the formation of the Zagros Mountains. In the east oceanic crust attached to the Arabian Plate is being subducted beneath the Eurasian Plate, causing uplift on the Iranian Plateau, which underlies Baluchistan, eastern Iran and the southwest of Afghanistan. This subduction is not a smooth process, with the rocks constantly sticking together then breaking apart as the pressure builds up. 

The approximate location of the 25 September 2013 Baluchistan Earthquake. Google Maps.

See also Magnitude 4.5 Earthquake in the Zagros Mountains of western Iran, Magnitude 4.8 Earthquake in the Zagros Mountains of western Iran, Magnitude 4.1 Earthquake in western Iran, Magnitude 4.5 Earthquake in southern Fars Province, Iran and At least 12 fatalities after a Magnitude 5.6 Earthquake in eastern Afghanistan.

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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.

See also Earthquake on the Kyrgyzstan/Uzbekistan Border, Earthquake in the Gulf of Corinth and Earthquakes on Sciency Thoughts Youtube.