MAY 1, 2003 BİNGÖL (TURKEY) EARTHQUAKE 

Preliminary Report (Updated on May 13, 2003)

After the earthquake, teams from both the Seismology Laboratory and the Earthquake Engineering Department of KOERI have been in the field. While the preliminary report prepared by the Seismology Department reveals interesting findings about faulting and mechanism, the work of the Earthquake Engineering team concentrates mostly on strong ground motion instrumentation and damage. 

TABLE OF CONTENTS

I.       Tectonics of the Region

II.      Aftershock Activity and Earthquake Mechanism

III.    Strong Ground Motion

IV.     Historical and Instrumental Seismicity

V.       Damage

VI.     Structural Performance in 1^st May 2003, Bingöl Earthquake

VII.    Pictures

I.   TECTONICS OF THE REGION

The tectonics of the region are controlled by the collision of the Arabian and Eurasian Plates. The northward motion of the Arabian plate relative to Eurasia causes lateral escape of the Anatolian block to the west (Ketin,1948, McKenzie,1972, Sengor,1979) and the Northeast Anatolian block to the east. The Anatolian block is bounded to the north and to the south-east by the North Anatolian and the East Anatolian faults, respectively.

The North Anatolian Fault (NAF) is the most eminent tectonic feature of the region and one of the best known strike slip faults in the world. It is an about 1500 km long, seismically active right lateral strike-slip fault system extending from the Karlıova triple junction in eastern Turkey to mainland Greece. Estimations on the age of the North Anatolian Fault range from late Miocene to early Pliocene (e.g. Sengor, 1985, Barka, 1992). The total relative displacement along the fault varies from 40 km in the east, near Erzincan, to 15 km in the west, near the Marmara Sea (Barka and Gulen, 1987).

Major tectonic entities of the region

The East Anatolian Fault Zone is a 550 km-long, approximately northeast-trending, left lateral strike-slip fault zone . The fault zone takes up the relative motion between the Anatolian and the Eurasian plates and, between the Arabian and African plates. The East Anatolian Fault Zone extends from Karlıova triple junction in the northeast to the Maraş triple junction in the southwest were it intersects the Dead Sea Fault. The age of the East Anatolian Fault is also highly debated. For instance Şengör et al. (1985), Dewey et al. (1986), Arpat and Şaroğlu (1972) place its formation in the Late Miocene-Early Pliocene. Zone is Pliocene (Barka, 1992). Şaroğlu et al. (1992) argue that the fault is Late Pliocene. Westaway and Arger (1998) suggested that the East Anatolian Fault Zone became active around 3 Ma.  Suggestions for the total left lateral displacement along the fault vary between 3.5-13 km and 15-27 km (e.g. Arpat and Şaroğlu, 1972, 1975, Şaroğlu et al., 1992). Only a few major earthquakes occurred on the East Anatolian Fault during the 20^th century. These are the December 4, 1905 (M=6.8) Malatya, September 28, 1908 (M=6.7), May 22, 1971 (M=6.8) Bingöl and May 5, 1986 (M=6.0) Sürgü earthquakes. Among those,the location of May 22, 1971 Bingöl earthquake is very close to the present earthquake which is also associated with the East Anatolian Fault system. 

 II.   AFTERSHOCK  ACTIVITY AND EARTHQUAKE MECHANISM

Field observations conducted by the Seismology Laboratory team are summarized on the figure in the right (Preliminary Report  prepared by the Seism. Lab.). Here the green circles show sites where fault traces, fault breaks in the surface,  settlements, landslides and toppled rocks were observed. Brown lines show active faults in the region as compiled by Saroğlu et al. (1992). The epicentral location of the 2003 Bingol earthquake agrees well with the NW-SE trending fault shown in the figure. The report associates the present earthquake with the N-NE trending fault passing from Kurtulus-ElmaCayiri-Hanocayiri and continuing towards  Balikcay-Cimenli.

Although the aftershock distribution with M>2 exhibits a somewhat diffuse pattern, the alignment of the aftershocks with magnitude >= 4.3 is also in agreement with the suggestion of NW-SE trending fault break (Preliminary Report  prepared by the Seism. Lab.). The epicentral locations of the aftershocks with M >= 4.3 are shown in the figure below. 

III.   STRONG GROUND MOTION

The earthquake was recorded by four strong motion recording stations operated by the Earthquake Research Department of General Dir. of Disaster Affairs ( http://angora.deprem.gov.tr/sond.htm). The horizontal peak ground accelerations are presented in the following figure. To view the accelerograms, please click on the hyperlinks in the table below.

11 strong ground motion recording instruments were installed by the Earthquake Engineering team as soon as the earthquake occurred. The locations of these stations are presented in the following figure. 

   Spectral Analysis of BNG record of the Mainshock

IV.   HISTORICAL AND INSTRUMENTAL SEISMICITY

May 22, 1971 M=6.8 Bingöl Earthquake

Isoseismal map of May 22, 1971 Bingö earthquake (Seymen and Aydın, 1972)

The northeastern segment of the East Anatolian Fault between the Karlıova triple junction and Bingöl is about 60 km long and is composed of many closely spaced parallel strike-slip faults strands. The 1971 Bingöl earthquake produced surface breaks mostly along the southwestern half of this segment. The relocated epicenter for the 1971 earthquake is at the southwestern end of the surface breaks. Although the exact locations are not known, two historical earthquakes of similar size, namely the 1789 and the 1875 events, are reported to have occurred in the vicinity of this segment (Barka and Kadinsky-Cade, 1988).

The 1971 event, preceded by a few foreshocks, caused considerable damage at Bingöl and its vicinity. Death of 881 and injury of 1157 people heve been reported. 3965 buldings were collapsed, 6950 buildings were heavily damaged, 9847 were moderately and 350 buildings were slightly damaged. The earthquake produced a belt of surface breaks, approximately 38 km long,  from SE of Bingöl to Cobantasi. Both field observations on surface breaks and earthquake mechanism solutions (Dewey, 1976; Taymaz et al.,1991) reveal a left-lateral strike slip geometry (Eyidoğan et al., 1991)

V.   DAMAGE

The municipality of Bingöl announced that in the city 308 housing units were collapsed, 2566 housing units were heavily damaged and 2546 housing units were lightly damaged.

Death of 168, and injuries of 520 people have been reported by the Government sources.

Currently our team is on the field, and information about damage will be updated regularly.
 

VI.   Structural Performance in 1^st May 2003, Bingöl Earthquake

The structural type of the city is generally composed of reinforced concrete buildings up to five or six stories, himis (buildings composed of timber frames and braces with adobe infills), and un-reinforced masonry structures. Both himis and masonry buildings are concentrated in the old city part (South West part) and the reinforced concrete buildings are concentrated in the north part of the city where the housing settlement has moved after 1971 earthquake.

Damage distribution of the structures is concentrated on the both sides of the river that passes through the city by dividing it into two. Most of the heavily damaged and collapsed structures are in Saray, Inönü, Yen, and Yenişehir districts.

As a result of the site investigations in the earthquake region, it has been indicated that significant portion of the government buildings (schools, dormitories, state buildings) have the highest level of damage in reinforced concrete structures. Also it has been seen that recently built (within 5 years) do not have significant damage.

Generally the structural performance of the building in the city center was not so good in such an earthquake, which can be said to a moderate one.

1.   Performance of Himis Buildings

Most of the himis buildings are located in Mirzan, Yeni and Yeşilyurt districts. Himis is widely used structural type of building in the Eastern part of Turkey that is built by their residents without engineering considerations. A typical himis building is composed of the thick perimeter walls and heavy roofs to provide heat isolation of the structure.

The observed performances of the himis buildings are not so good. Most of them had heavy damage and a few of them have totally collapsed. The major reason of this level of damage is the brittle behavior of the structural material that they are made of and poor strength of the connection between members. Also the high mass of the structure caused high lateral forces during seismic attack. On the other hand the weak connection of the braces between the members was not good enough to resist the lateral forces caused the total collapse structure.

Another important point is that; in almost all of the infill walls, the out of plane movement was not prevented and the collapsed infills caused non-structural damage.
 

2.   Performance of Unreinforced Masonry Buildings

In addition to the himis type of structures, there were also some un-reinforced masonry buildings in different regions of the city. Although their seismic performance is not good enough during earthquakes, unreinforced masonry buildings are preferred to reinforced masonry buildings in Turkey. But in the Turkish Seismic Code this issue is eliminated to some extent by limiting the story number according to the Seismic Zones. (e.g. max. 2 stories in seismic Zone 1). In addition to this some conservative connection detailing and force reduction factors are given to overcome this handicap.

Throughout the city the unreinforced masonry structures were heavily damaged. The common damage type was the typical “x-type” shear cracks due to the brittle behavior of the construction material. And in some of the buildings infill walls were partially collapsed due to the lack of restraints in the out of plane direction. This issue caused high level of non-structural damage like in himis structures.

As the seismic behavior of the structure is not taken into account, some connections are not detailed properly and this caused local and sometimes total collapse. Another reason for the damage is that these kinds of structures are build just following the traditional rules rather than the engineering principles.
 

3.   Performance of Reinforced Concrete Buildings

Like in the most of the Turkey, reinforced concrete structures are the majorty of the total structural stock in the city. The reinforced concrete buildings are mostly composed of columns and beams and a few of them have shear walls. Most of the reinforced concrete buildings in Inönü, Saray, Yeni and Yenişehir districts were heavily damage and collapsed. And in the other districts like Bahçelievler, Düzağaç and Yeşilyurt the reinforced concrete buildings were slightly damaged.

Generally the infill walls had shear cracks in buildings as Municipality Building, Telekom Building, Grand Bingöl Hotel, Banks and some slight damage on structural members. But the government buildings like schools ( Bingöl Lisesi, Mehmet Akif İlköğretim Okulu, Anadolu Güzel Sanatlar Lisesi, etc. ) Police Offices and Telekom Buildings were heavily damaged.

Among the observed damaged buildings the common type of failure was poor detailing at the critical region of the structural elements like insufficient amount of transverse reinforcement at the end region of beams, columns and beam column joints. On the other hand these connections had insufficient lap splice and transverse reinforcement.

Another type of failure was the poor quality of concrete. It has been learned that there was only one ready-mixed concrete plant in the vicinity. And the people do not prefer to use the ready-mixed concrete just because it is too expensive. Instead they produce their own concrete by using the material they get from Murat River as aggregate.

A few number of buildings had shear walls but in some cases due to insufficient transverse reinforcement and poor concrete quality wide shear cracks occurred in the shear walls. ( e.g. Bingöl Lisesi ). On the other hand recently built residential buildings that involve shear walls in their structural system, in Yeni and Yeşilyurt district, performed well during seismic attack.

It must be pointed out that the in addition to the structural damage on the structures significant amount of non-structural damage was observed. In the residential buildings the cabinet in the kitchens and rooms, bookshelves and televisions and other furniture fell down during seismic attack. Also in the schools bookcases, the pictures on the walls and florescent lamps fell down. And the out of plane collapse of the infill walls also caused non-structural damage.

As the result of the observations; it can be said that the structural damage was consecrated on both sides of the river ( e.g Saray and Inönü districts). And it must be emphasized that the seismic performance of the government buildings were so bad that the education in schools stopped, the hospital in the city center was partially out of service and the other buildings were so heavily damaged that it is almost impossible to retrofit these structures. The residential buildings were built without any engineering service and they are not controlled during their construction process. All of the reason listed above lead us to this much damage throughout the city.

Damaged villages in the vicinity of Bingöl                                   Districts in Bingöl City center

Damage Assessment Results 
(Data from the Ministry of Public Works and Settlement)

Districts in Bingöl City center

DAMAGE  DISTRIBUTION (Districts in Bingöl City center)

DAMAGE  DISTRIBUTION ( Villages)

VII.   PICTURES

Observed shear  failure at shear wall due to insufficient transverse reinforcement and poor concrete quality

Shear failure at column base due to insufficient amount of transverse reinforcement 

Collapsed first two stories

Çeltiksuyu Boarding School (Akşam newspaper)