2005 Qeshm earthquake

2005 Qeshm earthquake

The Portuguese fortress in Qeshm was damaged in the earthquake.
Date	November 27, 2005 (2005-11-27)
Magnitude	6.0 Mw
Depth	6.2 miles (10 km)[1]
Epicenter	26°47′02″N 55°50′49″E / 26.784°N 55.847°E / 26.784; 55.847Coordinates: 26°47′02″N 55°50′49″E / 26.784°N 55.847°E / 26.784; 55.847
Countries or regions	Iran,  United Arab Emirates
Tsunami	none
Casualties	at least 13 dead, 100 injured

The 2005 Qeshm earthquake was a powerful earthquake that occurred on November 27, 2005, at 13:52 local time (10:22 UTC) just west of a sparsely populated area of Qeshm Island off of Southern Iran. The earthquake was the second powerful one in Iran that occurred in 2005, following the Zarand earthquake in February. It killed 13 people and devastated 13 villages. The epicenter was about 1,500 kilometers (932 mi) south of Tehran in the Persian Gulf, close to the southern reaches of Iran, and measurements showed that the earthquake was about 6.0 on the moment magnitude scale. Over 400 minor aftershocks followed the main quake, 36 of which were greater than magnitude 2.5.

Because the earthquake occurred in a remote area during the middle of the day, it did not not cause many fatalities. Iranian relief efforts in the aftermath were effective and largely sufficient, leading Iran to decline offers of support from other nations and UNICEF.

Qeshm Island is an extension of the Zagros seismic area, sharing many characteristics with the highly active region, and is cut by at least two faults. The earthquake was a result of reverse slip faulting (which shortens and thickens the crust), and it created cracks in the nearby Ramkan syncline (a type of fold in the land). As it lies in such a seismically active area, Iran is at a high risk from destructive earthquakes. With 1 in 3,000 deaths in Iran attributable to earthquakes, one geophysicist has suggested that a country-wide rebuilding program will be needed to address the ongoing public safety concerns.

Background

Iran experiences at least one minor earthquake per day on average,^[2] and this particular region is prone to earthquakes. Seismic analysis has identified more than 80 earthquakes stronger than magnitude 5 in the last 100 years^[a], with large earthquakes recorded in 1360, 1703, 1884, 1897, 1902, and 1905.^[3] The majority of Iranian quakes occur in the upper crust, close to the surface.^[4]

Geology

The Arabian tectonic plate is converging with the Eurasian Plate, resulting in powerful Iranian earthquakes.

Iran's Zagros mountains form part of the Alpine-Himalayan belt, where north-south-trending convergence between the Arabian and Eurasian tectonic plates takes place at a rate of up to 25 millimeters (1 in) annually. Earthquakes in this region are predominately a result of reverse faulting, which creates folds like synclines and anticlines.^[5] The area is known for surface faulting (visible fracture in the surface rock) as a result of tension along deep "buried" faults, rather than major zones like those in the region. Qeshm is very similar to the mainland and Zagros in geological structure, the only major difference being that its faults trend from northeast-southwest and northwest-southeast rather than north-south. The faults on Qeshm Island converge to create a complex structure in the center of the island,^[6] where much of the tension in the 2005 Qeshm earthquake was observed. Along one of these northwest-southeast trending faults were the most concentrated levels of shear and dilatancy (volume change associated with application of shear stress) observed; shear and dilation were also recorded in the fault vicinity.^[7] Uplift around Qeshm has been going on throughout the Quaternary, and has created terraces of reef and beach atop Neogene-aged sediment.^[8]

The 2005 Qeshm earthquake measured 6.0 on the Moment magnitude scale,^[1][5][9] and was the second noteworthy Iranian earthquake of the year, preceded by the 2005 Zarand earthquake on February 22.^[10] The earthquake's epicenter was offshore in the Persian Gulf 44 kilometers (27 mi) west of Qeshm, close to the northern margin of the Arabian tectonic plate and near the front of the 'Simply Folded Belt', the most seismically active part of the Zagros fold and thrust belt.^[11][12] The focal mechanism (which describes the orientation of the fault that slipped and its movement direction) of this earthquake suggests it was a result of thrusting (where older rock is pushed over younger rock).^[11] This faulting has been confirmed as reverse slip (faulting which shortens and thickens the crust).^[13] The total displacement for the region was between 4 meters (13 ft) and 8 meters (26 ft), and uplift of anticlines was as much as 20 centimeters (8 in) in some places. The earthquake probably interrupted sedimentation, and may have created a discontinuity (fracture) in the rock closer to the surface.^[13]

If the earthquake had occurred during the morning while residents were asleep, rather than mid-afternoon (1:53 pm),^[14] it could have been deadlier. This is mainly because housing in the epicentral area consisted chiefly of mud and brick.^[15]

After the earthquake, a set of cracks appeared in a "limb" of the Ramkan syncline. The cracks suggested fracture of soil and were minor, but extended for approximately 3 kilometers (2 mi). Though they were parallel to the fracture in the Ramkan syncline's main body, the cracks were oblique to the fault thought responsible for the cracks and thus suggest that something also slipped in the syncline itself.^[8] Another short fracture was observed, but may be correlated with salt settling rather than faulting.^[16]

Damage and casualties

Lasting between 10 and 30 seconds,^[2][15][17] the earthquake hit at 13:52:19 local time, or 1:52 pm (10:22:19 UTC).^[5] It killed 13 people and injured 100 locals on Qeshm Island. In Zirang, a nearby village on Qeshm, 80 percent of the buildings were demolished. Thirteen villages were destroyed including Tonban, Ramekan, Gavarzin, Khaledin, Direstan, Kushe, Karavan, Turyan, Tom senati, Gorbehdan, Ziranag, Giahdan,^[11] and Gourian,^[18] seven other villages experiencing extensive damage.^[1]Mercalli scale Intensity III damage was reported in Bandar Abbas, and in Abu Zabi, Ajman, Dubayy, al-Fujayrah and Ras al Khaymah; Intensity IV damage (moderate) occurred at Sharjah.^[b] The earthquake was reported in Oman.^[1] No major damage occurred at the epicenter;^[19] residents of the city did report that the shaking burst windows, leading citizens to evacuate their homes in fear of collapse.^[17] In total more than 2,000 people were affected.^[20]

One major hospital crowded with the injured and lacking medical supplies for treatment and an airport on the epicentral island sustained damage, and power lines on the island were severed.^[17] Buildings in Dubai, including the Emirates Towers,^[21] were evacuated because of concerns they might collapse, but no such incidents occurred. The director of Tehran's seismological building dismissed fears of a tsunami, saying that the Persian Gulf was not "deep enough" to create one.^[14] In one school, some suffered broken legs when the building collapsed, but no fatalities occurred. One woman described the locals as "panicked".^[22] Television stations throughout Iran released footage of quake damage and of injured residents being taken to hospitals.^[23]

A damaging landslide^[15] and 36 major aftershocks of more than magnitude 2.5 (in total, 400 aftershocks) followed the earthquake.^[11] Damage at the eastern wall of an old Portuguese fortress eventually destroyed it. A Portuguese admiral stationed in Qeshm had ordered the fortress to be constructed in 1507.^[24]

Relief efforts

Aid workers from the domestic region began delivering supplies such as food, blankets, and tents.^[14] Around 74,151 tins of tuna fish, 40,920 kilograms (90,200 lb) of rice, 46,700 tins of canned beans, 10,445 kilograms (23,030 lb) of sugar, 16,836 kilograms (37,120 lb) of edible oil, 5,986 kilograms (13,200 lb) of pulse, and 1,133 kilograms (2,500 lb) of tea were distributed by the Iranian Red Crescent Society (IRCS). 4,696 sets of relief tents, 5,677 sets of moquettes, 10,689 sets of blankets, 2,169 kitchen sets, 1,477 ovens, 1,250 sets of lanterns and 4,001 cartons of hygienic kits were also given out by the organization. A dispatch of 101 relief helpers, 40 of the staff of the IRCS, and 4 people from the public relations department at ReliefWeb also assisted survivors. To help provide a structure to reliving efforts, 3 ambulances, 46 trucks, 3 helicopters, 12 vans, 9 cars and 2 minibuses and 2 sniffer dogs were also dispatched to help citizens of quake-struck areas.^[25]

Injured residents were evacuated via a helicopter, and were later transported to nearby Bandar Abbas.^[21] An Iranian police official, citing concerns about possible looting, said all movement of damaged houses would require prior approval from the governor's office, the police, and the Unexpected Events Committee on the island.^[26] UNICEF (United Nations Children's Fund) offered assistance to Iran, and the official in charge of response stated, "We are preparing to respond if needed".^[27] They elaborated that Iranian authorities "appeared to have things under control".^[27]

Future threat

Iran was listed as "the worst offender" in a 2004 report on countries with poor earthquake engineering.^[28] Professor Roger Bilham of the University of Colorado at Boulder, a geophysicist who specializes in earthquake-related deformation and hazards, blames construction practices for deaths in Iranian earthquakes.^[28] Since the start of the 20th century, 1 in 3,000 Iranians has died in an earthquake-related incident. Bilham argues that "Most of Iran needs rebuilding. If the population of Iran had a choice between spending oil revenues on munitions or houses that won't kill them, I suspect they would choose a safe home. It's all a matter of earthquake education."^[28] The United Nations has prepared a Common Country Assessment for Iran, which likewise states that "While adequate building regulations exist for large cities, it is generally believed that they are not rigorously adhered to ... most of those who have suffered in recent major earthquakes have lived in small towns and villages. Earthquake-proof construction is very rare in those areas and adequate building regulations are not yet in place".^[29]

The earthquakes of Iran are of significant concern to the populace, and an impediment to economic development. Twelve earthquakes with a magnitude of over seven have occurred within the last century. Three-quarters of Iran's major cities are in areas prone to major earthquakes. The 1990 Manjil-Rudbar earthquake, with at least 42,000 fatalities, cost Iran roughly 7.2 percent of its Gross National Product (GNP) for that year, and wiped out two years of economic growth.^[29]

In 2007, the Asian Centre on Seismic Risk Reduction was formed in response to the regular earthquakes experienced by the southern, southwestern, and central Asian areas. This organization exists to "encourage regional and inter-regional networking and partnerships to reduce seismic damage". Earthquakes account for 73 percent of natural disaster deaths in the area.^[30]

See also

Earthquakes portal

• 2005 Zarand earthquake
• List of earthquakes in Iran
  

Notes

• [a] ^ The strongest of these earthquakes occurred in Bandar Abbas in 1977, measuring surface wave magnitude 6.9.

• [b] ^ The Mercalli scale measures the intensity of earthquakes, mainly by their damage and their effect on the surrounding area.

References

Bibliography

• Nissen, Edwin, Ghorashi, Manoucher, Jackson, James, Parsons, Barry, and Talebian, Morteza (May 2007). "The 2005 Qeshm Island Earthquake (Iran)—A Link Between Buried Reverse Faulting And Surface Folding in the Zagros Simply Folded Belt?". Earth and Planetary Science Letters (Elsevier) 171 (1): 326–338. Bibcode 2007GeoJI.171..326N. doi:10.1111/j.1365-246X.2007.03514.x. http://www.earth.ox.ac.uk/~johne/pdfs/nissen-etal07b.pdf. Retrieved 2 July 2011. 
• Nissen, E., Yamini-Fard, F., Tatar, M., Gholamzadeh, A., Bergman, E., and Elliott, J.R. (June 2010). "The Vertical Separation of Mainshock Rupture and Microseismicity at Qeshm Island in the Zagros Fold-and-Thrust Belt, Iran". Earth and Planetary Science Letters (Elsevier) 296 (3–4): 181–194. Bibcode 2010E&PSL.296..181N. doi:10.1016/j.epsl.2010.04.049. 
• "United Nations Common Country Assessment for the Islamic Republic of Iran". United Nations. pp. 1–82. http://www.un.org.ir/documents/CCA_document.pdf. Retrieved November 23, 2009.