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|caption = Map showing the earthquake's epicenter |map alt = The earthquake's epicenter is shown in northeastern Iran. Just next to the earthquake is a mountain ridge. To the west is the Afghan border. |magnitude = 7.3 Mw |depth = |location = |type = Strike-slip |countries affected = Iran Afghanistan |damages = $100 million USD |intensity = X (''Extreme'') |casualties = at least 1,567 dead, 2,300 injured, and around 50,000 homeless〔 }} The Qayen earthquake, also known as the Ardekul or Qaen earthquake, struck Northern Iran's Khorasan Province on May 10, 1997 at 07:57 UTC (12:57 local time).〔〔 The largest in the area since 1990, the earthquake measured 7.3 on the moment magnitude scale and was centered approximately south of Mashhad on the village of Ardekul. The third earthquake that year to cause severe damage, it devastated the Birjand–Qayen region, killing 1,567 and injuring more than 2,300. The earthquake—which left 50,000 homeless and damaged or destroyed over 15,000 homes—was described as the deadliest of 1997 by the United States Geological Survey. Some 155 aftershocks caused further destruction and drove away survivors. The earthquake was later discovered to have been caused by a rupture along a fault that runs underneath the Iran–Afghanistan border. Damage was eventually estimated at $100 million, and many countries responded to the emergency with donations of blankets, tents, clothing, and food. Rescue teams were also dispatched to assist local volunteers in finding survivors trapped under the debris. The destruction around the earthquake's epicenter was, in places, almost total; this has been attributed to poor construction practices in rural areas, and imparted momentum to a growing movement for changes in building codes. With 1 in 3,000 deaths in Iran attributable to earthquakes, a US geophysicist has suggested that a country-wide rebuilding program would be needed to address the ongoing public safety concerns. == Background and geology == Iran experiences regular earthquakes, with 200 reported in 1996 alone.〔 Like dozens that had preceded it, the 1997 Qayen event was of significant magnitude. It occurred on Saturday, May 10, 1997, at 12:57 IRST in the Sistan region, one of the most seismically active areas of the country.〔 The first major earthquake in that region since 1979, it registered 7.3 on the moment magnitude scale (Mw), 7.2 on the surface wave magnitude scale (Ms), 7.7 on the energy magnitude scale (Me), and had a maximum perceived intensity of ''X'', or ''Extreme'' on the Mercalli intensity scale.〔 The earthquake was caused by a rupture along the Abiz Fault, part of the Sistan suture zone of eastern Iran. Located northeast of the main collision zone between the Arabian and Eurasian tectonic plates, the Sistan zone marks the eastern boundary of the Iranian microplate where it intersects with the Afghan crustal block.〔 Most of Iran is contained on one microplate, causing seismic activity mainly along its borders. Both the 1968 Dasht-e-Bayez earthquake (magnitude 7.3, resulting in 12,000–20,000 deaths) and the Qayen earthquake were the results of strike-slip faults, meaning that the crustal blocks on either side of the faults shifted against each other horizontally.〔 The Qayen earthquake was caused by right lateral movement along the Abiz Fault. In addition to the dominant strike-slip displacement, there was also local evidence of reverse faulting. The average displacement of about 2 m indicates a low static stress drop, more consistent with an interplate earthquake than an intraplate event.〔 The maximum horizontal acceleration during the quake was approximately 6.9 meters per second—nearly three-quarters of the acceleration an object would have in free fall—and occurred near the earthquake's epicenter. The crustal layer involved in the rupture was thick. The surface fault that caused the earthquake extended for , which was longer than would be expected given the earthquake's magnitude.〔 There were at least 155 aftershocks, reaching a magnitude of up to 5.5 on the Richter magnitude scale.〔 Many of the aftershocks occurred along the rupture up to below the surface.〔 The earthquake's epicenter was within the village of Ardekul〔 in South Khorasan Province, which borders Afghanistan. The village is isolated between mountains and hills. Although the Iranian government had distributed more than 800 seismographs throughout the country, few had been placed in the Qayen region due to its desert climate and the remoteness of the area.〔 As a result of the dry climate, timber—a main component in building earthquake-resistant homes—is scarce in Qayen; homes are instead constructed of adobe.〔 The inhabitants of the poverty-stricken region rely on subsistence farming, raising livestock and crops such as wheat and saffron.〔 When the earthquake struck, much of the population was already working in the fields; for the most part, these people survived.〔 Many of those treated for injuries were found to be undernourished.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1997 Qayen earthquake」の詳細全文を読む スポンサード リンク
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