UPDATE: Turkey Quake Toll Mounts; Rescue Work Continues; AIR Analysis

October 25, 2011

As rescue workers continued their efforts to find survivors in the debris from collapsed buildings, the death toll from Monday’s earthquake continues to rise. Local officials have said that 279 bodies have been recovered so far, but many more are feared to lie beneath the rubble. More than 1300 people have been injured.

According to catastrophe modeling firm AIR Worldwide, it is still too early to clearly assess the damages caused by the quake, mainly in the eastern cities of Van and Ercis, but it ” is widespread, and aftershocks, of which there have been more than 200, remain a concern. The U.S. Geological Survey has issued a moment magnitude estimate of 7.2 for the event and a relatively shallow focal depth of 20 km, which will have exacerbated the damage.”

Dr. Mehrdad Mahdyiar, director, earthquake hazard at AIR Worldwide explained that the “tectonic setting of Van province is dominated by the collision of Arabian and Eurasian plates. The Arabian Plate moves northward at a rate of about 15-20 mm/yr and collides with the Eurasian plate in eastern Turkey. The collision of the two plates squeezes the Anatolian plate in central and western Turkey to move westward, resulting in the formation of one of the longest strike-slip faults in the world—the Northern Anatolia fault. Many of Turkey’s most severe quakes occur on this fault, including the devastating 1999 Izmit earthquake.”

The quake lasted for more than 30 seconds and was felt throughout the country, and as far away as parts of neighboring countries of Armenia, Azerbaijan, Georgia, Iran, Iraq, and Syria. AIR said the “hardest hit areas appeared to be around the town of Ercis, where up to 80 multistory buildings collapsed, including student dormitories, apartment buildings and hotels. According to the prime minister’s emergency agency, the earthquake has destroyed or damaged 970 buildings in the region. Officials estimate the number of fatalities could be as high as 1,000.

“According to AIR, in Turkey, ground floors are commonly used for commercial purposes, with residential units above. The large shop windows and other openings on the ground floor reduce the lateral resistance significantly, resulting in excessive deformation demands. Asmolen construction, a form of reinforced concrete frame that has a joisted floor slab made of hollow cement cinderblock, is commonly used in Turkey.”

The bulletin also noted that AIR has conducted previous “post-disaster surveys in Turkey,” which found that the “blocks were often discovered to be not properly attached to the reinforced concrete floor, and floor damage such as the dislodging and falling of hollow blocks was widespread. Additional damage was observed due to structural irregularities, a lack of transverse reinforcement, and short columns.”

To correct these and other structural weaknesses, following the catastrophic Izmit earthquake that killed nearly 20,000 people in 1999, the “Turkish government introduced new construction codes that were intended to address these design deficiencies and ensure that new construction would withstand ground shaking similar to that produced by Monday’s earthquake.”

However, Dr. Mahdyiar explained that “many buildings in Van will have been built before the new code. Moreover, code enforcement has long been an issue in Turkey; it was observed after the 1999 Izmit and Düzce earthquakes, for example, that many structures built in 1999 did not follow the 1998 regulations.

“Experts believe, however, that codes have been more seriously enforced after 2000. In 2006, the Turkish Earthquake Code was updated again, but its seismic provisions are similar to the existing 1998 code. Undoubtedly, many questions will be raised regarding code enforcement in the weeks ahead.”

AIR also pointed out that, “although a national earthquake insurance pool was established in Turkey in 2000 and participation is mandatory for all general insurance and reinsurance companies, earthquake insurance penetration is still generally low.

“In collaboration with the World Bank, the Turkish government and the private insurance industry, the TCIP (Turkish Catastrophe Insurance Pool) was established as a way to provide earthquake insurance cover for residential properties. The terms of TCIP coverage are relatively simple, with the losses covered up to a maximum of TRY 150,000 [$83,033] including a deductible of 2 percent. Insurance penetration, particularly in eastern Turkey, remains relatively low—between about 2-10 percent in the area impacted by yesterday’s earthquake.”

Source: AIR Worldwide and news reports

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