Catastrophe modeling firm AIR Worldwide estimates that insured losses from the M7.2 earthquake that struck eastern Turkey Sunday, October 23rd, near the city of Van will be between 100 million TRY (55 million USD) and 300 million TRY (170 million USD). (The range in losses results from uncertainties that exist in estimating earthquake source parameters e.g., magnitude, rupture length, depth, dipping angle, etc.)
Today, the third day since the Van earthquake, aftershocks continue in eastern Turkey. At least 400 aftershocks above M 3.0 have been reported in total, with the strongest of these registering M 6.0. The Van earthquake is the largest to strike Turkey since the 1999 magnitude 7.2 Duzce earthquake, which killed more than 1,000 people and caused significant structural damage.
According to AIR, Turkey has a high rate of earthquake occurrence. Within the past twenty years alone, there have been seven earthquakes with magnitude of greater than 6.0 in the region of the Van earthquake. In Van province, the tectonic setting is dominated by the collision of the Arabian and Eurasian plates; this collision squeezes the Anatolian plate located in central and western Turkey 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.
Up to 80 multistory buildings in total-including student dormitories, apartment buildings and hotels-are destroyed in Ercis. Elsewhere, in the district of Celebibag, several buildings collapsed. The earthquake was felt not only in Van Province, but in the provinces of Bitlis, Muş, Batman, Ağrı, Diyarbakir, Mardin, Erzurum, Siirt, Sirnak, İskenderun, and Hatay. The tremor also shook buildings in neighboring Iran and Armenia, though significant damage has not been reported in either country.
Unlike urban centers in western Turkey, where construction is dominated by reinforced concrete, the majority of construction in Van province is unreinforced masonry, according to the Kandilli Observatory and Earthquake Research Institute. At the sub-provincial level, in Ercis, the majority of buildings are unreinforced masonry as well, though roughly a quarter are reinforced concrete, the latter of which better withstands earthquake ground motion. An even smaller fraction of buildings can be classified as adobe and rubble stone, both of which are very vulnerable to seismic activity. Indeed, the high vulnerability of adobe and rubble stone, as well as the slightly lower vulnerability of unreinforced masonry construction, comparatively, are partly to blame for extensive damage in Ercis.
According to the Disaster and Emergency Management Agency of Turkey as of October 24, more than 2,000 buildings have sustained damage ranging from moderate to complete; the geographical and structural distribution of affected buildings is still being determined. Despite this uncertainty, patterns discernible thus far reveal that the damage from Sunday’s quake is similar to that from past events in Turkey, marked by inadequate reinforcement, lack of confinement at beam-column connections, low quality concrete and soft first stories of buildings. In Turkey, first (ground) floors are commonly used for commercial purposes, with residential units above. The large shop windows and other openings typical in the ground floors of these buildings reduce the lateral resistance significantly, resulting in excessive deformation demands.
Based on current damage reports, the Kandilli Observatory and Earthquake Engineering Institute estimates that 3% of the buildings in the province were damaged beyond repair by Sunday’s quake.
According to AIR, a new building design code was enforced in Turkey in 1998, though there were several enforcement issues with this new code; these became evident following the 1999 Izmit and Duzce Earthquakes, during which several newer buildings sustained severe damage. In the aftermath of these earthquakes, more attention was paid to code enforcement and adoption issues. Experts believe that building design codes have been more seriously enforced since 2000.
In 2006, the Turkish Earthquake Code was updated again, but its seismic provisions are similar to the existing 1998 code. During the weekend’s earthquake, many new buildings were damaged, and thus, in the weeks ahead, as damaged buildings are inspected, questions will again be raised regarding code enforcement.
Sunday’s earthquake occurred in a broad zone of compression caused by the collision of the Arabian and Eurasian plates, according to AIR. Most of the earthquakes in eastern Turkey are strike-slip and thrust ruptures; consistent with the tectonic stress field in the region, the mechanism of the Van earthquake indicates an oblique thrust faulting system. The quake struck about 70 km from where a M 7.3 earthquake occurred in November 1976, killing thousands, and 1000 km from the devastating M 7.6 Izmit earthquake, which killed nearly 20,000 people.
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. Indeed, insurance penetration in eastern Turkey, in the areas affected by Sunday’s earthquake, are estimated at roughly 8%.
Note that AIR’s industry insured loss estimates include: * Insured physical damage to property (residential; commercial/industrial), both structures and their contents. The residential insured losses include estimated losses for the TCIP (Turkish Catastrophe Insurance Pool).
The loss estimates do not reflect:
* Losses from non-modeled perils, including landslide and fire-following;
* Losses to automobiles;
* Losses to uninsured properties;
* Losses to land;
* Losses to casualty and life lines;
* Losses to infrastructure;
* Business interruption losses;
* Loss adjustment expenses;
* Demand surge-the increase in costs of materials, services, and labor due to
increased demand following a catastrophic event.
*Conversion rate used is 1 USD = 1.77 TRY