CoreLogic estimates industry insurable losses in Turkey could exceed $4.0 billion
A sequence of powerful earthquakes struck near the Turkey-Syria border beginning late on Feb. 5 and continued through the morning of Feb. 6. Three of the earthquakes had magnitudes (M) exceeding 6.5.
Event Description and Earthquake Parameters
On Feb. 6 at 4:17 a.m. local time (1:17 a.m. UTC), an M7.8 earthquake occurred in southern Turkey near the northern border of Syria. According to the U.S. Geological Survey (USGS), an M6.7 aftershock followed 11 minutes later.
The original earthquake and subsequent aftershock struck at shallow depths of 17.9 km (11.1 miles) and 14.5 km (9.0 miles) beneath the ground surface, respectively. The event ruptured either a near-vertical, left- or right-lateral fault, striking northeast-southwest or southeast-northwest, respectively. Peak 1-Second Spectral Acceleration (SA 1.0) of up to 50% g (Figure 1, left) and 20% g (Figure 1, right) were recorded for the M7.8 earthquake and M6.7 aftershock, respectively.
Figure 1: Peak SA (1.0) maps of the M7.8 earthquake (left) and M6.7 (right) aftershock near the Turkey-Syria border on Feb. 6.
On Feb. 6 at 1:24 p.m. local time (10:24 a.m. UTC), an M7.5 earthquake struck 95 km (59.0 miles) north of the Turkey-Syria border at a shallow depth of 10.0 km (6.2 miles) beneath the ground surface. This earthquake occurred nine hours after the initial event.
According to the USGS, the M7.5 earthquake ruptured either a near-vertical, left- or right-lateral fault, striking east-west or north-south, respectively. Peak 1-Second Spectral Acceleration (SA 1.0) of up to 20% g (Figure 2) was recorded for the M7.5 earthquake.
Figure 2: Peak SA (1.0) map of the M7.5 earthquake near the Turkey-Syria border on Feb. 6.
Both the M7.8, including subsequent aftershocks, and M7.5 earthquakes occurred near the triple-junction of the Anatolia, Arabia and Africa plates within the East Anatolia fault zone. The East Anatolia fault zone extends westward from Turkey into the Aegean Sea.
Historically, the Anatolia fault zone is an active seismic region. Since 1970, there have been three earthquakes with a magnitude of six or greater within 250 km (155.3 miles) of the Feb. 6 sequence, according to the USGS. The most severe was an M6.7 earthquake that occurred on January 24, 2020. Throughout history, Aleppo, Syria, has experienced several devastating earthquakes, including an M7.1 in 1138 and an M7.0 in 1822. The latter was responsible for 20,000 to 60,000 fatalities.
The Hazard
Ground shaking with a maximum intensity of nine on the Modified Mercalli Intensity Scale (MMI) was recorded during the Feb. 6 earthquake sequence. According to the USGS, MMI 9 represents violent ground shaking that can cause considerable damage even in structures designed to mitigate the effects of earthquakes. A higher degree of damage, including partial collapse, is expected in poorly constructed buildings.
According to the USGS PAGER, approximately 5.5 million people felt ground shaking with an intensity of MMI 7 or greater, and 70,000 people were subjected to ground shaking of MMI 9. MMI 8-level ground shaking was reported in Gaziantep, Turkey, approximately 36.0 km (22.3 miles) from the M7.8 earthquake epicenter.
Residents of Aleppo, Syria, reported ground shaking with MMI 7 intensity. Shaking was reported as far as Cyprus and Ankara, Turkey. Structures in southeastern Turkey and northern Syria are predominately constructed with unreinforced brick masonry and low-rise, non-ductile concrete frames. Both construction materials are extremely vulnerable to ground shaking.
Turkey first developed building codes in 1940. The codes have since been updated, with major revisions in 1959, 1975, 1998 and 2007. However, enforcement of these codes has been minimal.
Reported Damage in Turkey and Syria
Initial reports indicate substantial damage and fatalities from the areas of Turkey and Syria that were hit hardest during the Feb. 6 earthquake sequence. As of the morning of Feb. 7, over 3,700 fatalities were attributed to the earthquake sequence. The Turkish president reported over 2,800 structures collapsed. More than 1,400 people lost their lives in Syria due to the earthquakes. These numbers are expected to rise.
RQE Model Users: Proxy Events and Modeled Insurable Loss
Clients who license the CoreLogic Turkey Earthquake Model on RQE can download proxy events from the stochastic catalog and modeled insurable loss from the Catastrophe Modeling Client Resource Center (CRC) at: https://crc.corelogic.com/.
