ORI GIN AL PA PER

October 23, 2011 Turkey/Van–Ercis earthquake:structural damages in the residential buildings

Erkan Celebi • Muharrem Aktas • Naci Caglar • Askın Ozocak •

Mustafa Kutanis • Necati Mert • Zeki Ozcan

Received: 27 January 2012 / Accepted: 26 October 2012 / Published online: 16 November 2012� Springer Science+Business Media Dordrecht 2012

Abstract On October 23, 2011, a magnitude of Mw 7.2 earthquake struck the Van

province in eastern Turkey which caused approximately 600 life loss and 4,000 injured

people. Although the recorded peak ground accelerations were relatively low (0.15–0.2 g)

compared with that of other recent destructive Turkish earthquakes and the code-based

design response spectrum, a large number of reinforced concrete buildings with 4–6 stories

and non-engineered masonry buildings were either heavily damaged or collapsed in the

region. Based on the post-earthquake technical inspections, the goal of this paper is to

introduce major reasons for structural damages in the disaster area and to discuss these

failures along with the approaches given in the design code which is renewed after August

17, 1999 Marmara Earthquake. Some remarkable lessons learned from earthquake-induced

failures and damages specific to building construction techniques are presented in this

paper.

Keywords Van earthquake � Structural failures � Reinforced concrete structures �Masonry buildings

1 Introduction

After the earthquake of Marmara (on August 17, 1999), during the last decade, Turkey has

suffered several destructive seismic events (Afyon Sultandagi Mw 6.1, 2002; Bingol Md

6.4, 2006; Elazig Kovancilar, ML 6.0, 2010; Kutahya Simav ML 5.7, 2011) that caused life

loss and injuries. On October 23, 2011, at 10:41:20 UTC, a magnitude of Mw 7.2 earth-

quake struck the Van province in eastern Turkey. The Earthquake Department of the

Disaster and Emergency Management Presidency (AFAD) reported the earthquake’s

epicenter as 38.689 N–43.465E with the depth of 19.02 km. The fault rupture propagation

was along the northeast and southwest directions, and the faulting mechanism was reverse

E. Celebi � M. Aktas (&) � N. Caglar � A. Ozocak � M. Kutanis � N. Mert � Z. OzcanDepartment of Civil Engineering, Engineering Faculty, Sakarya University,54187 Esentepe-Sakarya, Turkeye-mail: muharrema@sakarya.edu.tr

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with a fault surface area of 60 km 9 20 km. The average displacement on the fault surface

at a depth of 10–15 km was 2 m (KOERI).

Earthquake epicenter was located directly between Ercis district and Van City. The

officially reported populations of Van City and Ercis district are 367.419 and 77.065,

respectively. The total population of Van province has been estimated around 1.035

million. Ercis district was the most heavily damaged area in this earthquake. The

total number of 548 citizens in Ercis district and 61 citizens in Van city are confirmed

death.

This paper presents the on-site structural investigations of a team consist of 7 acade-

micians from Civil Engineering Department of Sakarya University, Turkey after Van

earthquake.

2 Tectonic settings overview

General tectonic setting of Eastern Anatolia is mainly controlled by collision of unevenly

moving Arabian plate to the north with the Anatolian plate along a deformation zone

known as Bitlis Thrust Zone (Fig. 1). The collision leads westward extrusion of the

Anatolian plate along the two notorious transform faults with different sense of slip, the

dextral North Anatolian Fault and the sinistral East Anatolian Fault Zones, which join each

other in Karlıova Triple Junction (KTJ) in the Eastern Anatolia (Fig. 2). In the east of KTJ,

however, the collision-caused deformation is largely accommodated within the Eastern

Anatolian Block through distributed NW–SE trending dextral faults and NE–SW trending

sinistral faults representing escape tectonics, and shortening of the continental lithosphere

along the Caucasus thrust zone. East–west trending Mush-Lake Van and Pasinler ramp

basins constitute other conspicuous tectonic properties within the Eastern Anatolia (Utkucu

2006).

The faults are seismically active and they form the source for many earthquakes. Some

of the major earthquakes in the twentieth century are September 13, 1924 Pasinler

(M = 6.8), 1975 Lice (M = 6.6), November 24, 1976 Caldıran (M = 7.3), October 30,

1983 Horasan–Narman (M = 6.8), May 5, 1986 (M = 5.8) and June 6, 1986 Dogansehir

(M = 5.6) earthquakes (Bozkurt 2001).

3 Strong ground motions and response spectra

Turkish National Strong Ground Network operated by AFAD recorded the strong ground

motion data for calculating the peak acceleration values for 23 October Van earthquake.

The peak acceleration values recorded at Muradiye Station were 178.5, 169.5 and

79.15 cm/s2 in north–south, east–west and vertical direction, respectively. Time history

plots for earthquake records are given in Figs. 3, 4, 5.

Figure 6 provides a comparison of response spectra of N–S and E–W components of

Muradiye station records with the code-based spectrum. Both components are below the

design spectra defined for high-seismic zones in Turkey. In Fig. 6, it is observed that both

response spectra components are below the design spectra and the range of frequencies

which are bounded approximately by 2 and 4 Hz are very close to fundamental period of

damaged structures in Ercis.

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4 Geological and geotechnical overview

4.1 Geological overview

Van Lake Basin is originated with rock groups of different origins and wide range age of

Paleozic age to actual deposits (Fig. 7). South of the basin is formed by the metamorphic

rocks belonging to Bitlis Massive, and west and north of the basin is covered with the

young volcanic and volcaniclastic rocks. The east part is covered with Mesozoic aged

oceanic cover, and complex (melange)-structured rocks were formed. Small basins located

in east–west direction are full of young-actual alluvial and lacustrine deposits and car-

bonates, related to neotectonic event at Senozoic period (Ciftci et al. 2008).

In Degens et al. 1978, it is stated that Van Lake reached its maximum level 16,000 years

ago and draw back 10,000 years ago. Researchers claim that marine environment left its

place to terrestrial environment at the late of Miosen.

Faults and opening cracks appeared, and volcanos in East Anatolia are presented in

neotectonic period (Fig. 8). Alive fault map of Van zone was presented in Fig. 2. There is

no live fault in Fig. 2, but existence of embedded faults can be seen near the epicenter of

the 2011 earthquake with the dashed line in Fig. 8. According to this phenomenon, it may

be thought that magmatism may still be active in this region.

Fig. 1 Major tectonic elements of Eastern Turkey that taken from (Saroglu et al. 1992). MRB Mus RampBasin, PRB Pasinler Ramp Basin, KTJ Karlıova Triple Junction. Large rectangle encloses the map areashown in Fig. 2, black filled triangles show the location of Suphan and Nemrut volcanoes (SV and NV,respectively), and large arrows indicate relative plate motions (Utkucu 2006)

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4.2 Geotechnical overview

Old lacustrine deposits that form the Van plain consist of uncemented gravelly, sandy and

silty levels. The most encountered form of soil is sand and silt in the area. Gravelly and

clayey levels are observed generally in thin bands. Lacustrine deposits are observed at

1,800 m level.

Fig. 2 The map showing tectonic features, M C 4.0 seismicity and known source mechanism solutions ofLake Van area along with the bathymetry of Lake Van. The M C 5.0 earthquakes after 1860 are shown withwhite and black filled stars (macroseismic and instrumental epicenters, respectively). The 4.0 B M \ 5.0earthquakes after 1970 are denoted by black and dark gray filled circles. Black filled circles with assignednumbers show the 4.0 B M \ 5.0 earthquakes selected for the correlation with the water-level changes ofLake Van. Large open triangles indicate the location of the Nemrut and Suphan volcanoes. The faultslabelled as I, II, III and IV were adapted from Ketin (1977). SBF Southern Boundary Fault, NFZ NorthernBoundary Fault, C¸FZ C¸ aldıran Fault Zone, MF Malazgirt Fault, TF Tatvan Fault, KFZ Karayazı FaultZone, EFZ Ercis Fault Zone, TFZ Tutak Fault Zone, TB Tatvan Basin, DB Deveboynu Basin (Utkucu 2006)

Fig. 3 October 23, 2011 Van earthquake acceleration time history N–S component for Muradiye (6,503)station

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Definition of Van formation (Tmv) was first done for the formation pattern at the east of

Van Lake. Van formation is originated by generally fragmentally rocks and by thin-

medium, rarely thick-layered sandstones and thin-layered shales. Foliation is seen at some

sections because of the tectonic affects.

Sand dimensioned material is generally silty and poor-graded class in lacustrine

deposits. Gravels of maximum grain size 5 cm are formed by partly merged ophiolitic

pieces. There are 7�–24� of slopes formed to settle through Van Lake at lacustrine and

alluvial deposits. This slope does not have tectonic basis that took place during the sedi-

mentation (Aksoy 1988).

During the site observation at the city center of Van, it was seen that clay additively but

not fully uncemented sand–gravel layers under the organic soil could hold up itself at 90�in a 1.5-m-deep open foundation pit that is located near the building completely collapsed

Fig. 4 October 23, 2011 Van earthquake acceleration time history E–W component for Muradiye (6,503)station

Fig. 5 October 23, 2011 Van earthquake acceleration time history vertical component for Muradiye (6,503)station

Fig. 6 Damped linear response spectra [5 %] for Muradiye station records obtained during October 23,2011 Van earthquake and comparison with the code-based spectrum

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in the earthquake. There was no soil problem noted down for collapsed, heavily damaged

and undamaged buildings in the city center of Van.

Also, in the district of Ercis, there were no structural deformations related to soil

properties under the structure. In the area, soil can be classified as hard clay and clayey

sand–gravel levels, and it supplied enough bearing capacity and met the settlement criteria

for the buildings which generally have 4–8 stores (see Fig. 9). For example, in Van city

center, there was no deformation observed in 10-m-deep excavation which was supported

by poor anchoraged piles (see Fig. 10).

Sand cones which signed the liquefaction phenomena were observed in the wide pasture

field of Topaktas village which is close to the city center (Fig. 11a). The pasture field is a

wide flat area near the Mermit stream that gets a lot of water when the stoppers of

Sarimehmet Dam are opened. According to a resident from Topaktas village, during the

earthquake, there were sand and water gushing out and reaching up to 5 m from the ground

at this pasture field. He also added that he did not meet the sand layer when he bored a well

at the area before the earthquake. Thus, liquefiable sand layers are located more than 7-m

depth. Grains of gravel dimension are also seen in the same area. This also supports the

Fig. 7 Geological map of Van Lake Basin (Ciftci et. al. 2008)

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Fig. 8 Volcanos appeared atneotectonic term in East Anatolia(Bol 1993)

Fig. 9 Soil section of an open foundation pit (Ercis District)

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idea of gravel liquefaction. Moreover, lateral spreading deformations resulting with liq-

uefaction were also observed on the field (Fig. 11b).

In addition to this, landslides were observed at the natural slopes which the Mermit

stream flood near its skirt and artificial slopes which were formed near the sand quarry

(Fig. 12a, b).

5 Structural failures of the reinforced concrete structures

5.1 Poor concrete quality

In the Turkish Earthquake Code, it is clearly expressed in section 3.2.5 of that the mini-

mum characteristic strength of concrete must be at least 20 MPa for reinforced concrete

structures to be built in earthquake active zones (TEC 2007). However, in Ercis district, the

characteristic strength of concrete for the most damaged RC buildings is well below that

value. Diyarbakir Chamber of Civil Engineers (DCCE) investigated the characteristic

strength of concrete by drilling cores from 6 destroyed RC buildings and conducting

compression tests on them. It is reported by DCCE that the characteristic strength

of concrete varied between 4.70 and 15.60 MPa with the average value of 9 MPa

(Bedirhanoglu 2011).

At the field investigation, it is found that the handmade concrete is generally used and

sand obtained from dried river bed is used without processing it to be suitable for concrete

production (Fig. 13). In other words, aggregates containing high percentage of organic

materials and washable particles like clay and silt with coarse material are used in concrete

production. Moreover, it is observed that the aggregate used in most buildings did not

possess a particle size distribution. The aggregate dimensions are observed to be around

4–5 times larger than the maximum aggregate diameter allowed for concrete (Fig. 14).

Fig. 10 Deep excavation with poor anchoraged piles (Van City center)

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5.2 Poor reinforcement detailing

The most critical regions in a structure subjected to earthquake are column ends and beam–

column joint connections. Therefore, Turkish Earthquake Code has significant limitations

about the dimensions and reinforcement details of these regions in order to improve the

strength and ductility of the structural elements and structure. It was observed that the

confinement reinforcement such as cross-ties did not exist in the first 30–40 cm region at

column-foundation connections (Fig. 15) and the beam–column connections (Fig. 16).

Fig. 11 a Sand cones, b gravelcones and lateral spreadings metat Topaktad pasture field

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Many of the beam–column and column-foundation connections are heavily damaged as

a result of absence of confinement reinforcement, wide spacing of the cross-ties and

insufficient lateral cross-ties at these joints. Because of these insufficiencies, spilling of

Fig. 12 a Artificial slopes, b natural slopes slided during the earthquake in Topaktas village

Fig. 13 Typical concrete quality of RC elements

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cover and core concrete and buckling of longitudinal reinforcing bars are observed in many

damaged RC buildings (Fig. 17a).

Moreover, several number of detailing deficiencies such as using inadequate hook, 90�hooks for cross-ties (Fig. 17b) and insufficient overlap lengths are also observed in the

heavily damaged buildings.

Fig. 14 Particle size distribution in concrete

Fig. 15 Column-foundationconnections

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5.3 Soft story buildings

The commercial usage of the ground stories without having reinforced structural wall

systems and unreinforced masonry infill walls, which induced soft and weak stories in

reinforced concrete buildings, is one of the substantial reasons for the heavy structural

damages and building collapses observed in earthquake region. The stores designed with

wide openings at ground floor level are generally surrounded by glass windows instead of

masonry infill walls. Upper floors considered as housing units have heavy masonry walls,

while the base floors do not have adequate shear resistance in the affected area. The high

ductility demand and overall shear forces imposed to the building, which occurred

instantaneously at the first floor during earthquake, could not be properly fulfilled by using

lateral load-resisting structural systems with having poor reinforcement detailing without

satisfying the requirements of seismic code. Because of the sudden discontinuities in the

lateral rigidity and strength between the adjacent stories, the soft story building cannot

dissipate the seismic energy as required. In this case, shearing failures such as crushing of

core concrete on column ends and anchorage dissolving with buckling of longitudinal bars

at joint connections are observed due to the demand of undesirably large drift and seismic

energy dissipation during earthquake-induced building movement.

The stability of individual column members and the entire structure are influenced by

increased number of plastic hinges, which leads to collapse mechanism in many floors due

to p-delta effects. Thus, the upper floors with limited damage are collapsed on the ground

story. The soft story effects on collapsed apartment buildings in both the center of Van and

Ercis district shared a common failure feature that can be seen from Fig. 18a, b. Turkish

seismic code has included special design provisions to avoid soft story behavior and weak-

story irregularities.

5.4 Ribbed slab construction

In the affected area, it is observed that the rib beam slab systems are widely used as floor

members in reinforced concrete building. Inspections of earthquake-induced structural

Fig. 16 Beam–column connections

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damages in the epicenter region have shown that many residential structures with one-way

spanning asmolen (lightweight gas-concrete block) slab systems creating inadequate shear

resistance, are heavily damaged. As shown in Fig. 19, four-story trade center building in

(a)

(b)

Fig. 17 Detailing deficiencies in structural elements. a Buckling of longitudinal reinforcing bars,b inadequate hook detailing

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Ercis district which was under construction during earthquake is a good example to

discuss.

In ribbed slabs, strong column–weak beams are usually formed. Thus, designer should

take actions against reduced lateral stiffness of the structure in both directions. In Van, it

was observed that the improper orientation and location of the limited number of the shear

walls with non-ductile detailing resulted in extreme failures. Asmolen floor framing pos-

sessing thin slab thickness has low lateral load carrying capacity in one-way direction,

perpendicular to the street (Fig. 20). Thus, plastic hinges are concentrated on all column

ends in the long direction (parallel to the street) of this trade center (Fig. 21). Therefore,

(a)

(b)

Fig. 18 Failures due to soft story action. a From Ercis District, b from Van City

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using shear walls for both directions in a ribbed slab system may prevent collapses or

lateral drifts. In ribbed slab system, the case of badly oriented columns and lack of shear

walls can be a reason for damage.

5.5 Strong beam and weak column behavior

In earthquake-resisting structure design, one of the important points is to avoid the strong

beam–weak column behavior. The main purpose of this approach is to enable the weak

element, that is, beams, to lose their bearing capacity initially and contrary to enable the

columns to stand for a while to provide living space for people. To achieve this behavior,

Turkish Earthquake Code section 3.3.5 requires the sum of bearing capacity moments of

columns should be at least 20 % more than the sum of bearing capacity moments of beams

at the same joint for structures which resist the earthquake effects by frames or frame–wall

combination (TEC 2007). Doing so, will create plastic hinges at the end of the beams. It is

Fig. 19 Trade center having one-way spanning asmolen slab systems

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observed that many multi-story buildings collapsed because of strong beam and weak

column type connection (Fig. 22). As mentioned in the previous section, poor reinforce-

ment detailing was also present in such connections.

5.6 Unconfined gable walls

The most common earthquake damage observed in the roofs is the collapse of the gable

walls (Fig. 23). The reason of the vast majority of the collapse of the gable walls is because

they are not adequately connected to the structure and they are constructed with missing

lintels. However, it is stated in the masonry building section of Turkish Earthquake Code

5.7.3 that in the case where the height of the end wall (gable wall) resting on the horizontal

lintel at the top story exceeds 2 m, vertical and inclined lintels shall be constructed (TEC

2007). This condition is not met for the majority of buildings that are damaged in the

Fig. 20 Shear cracks on structural walls and on columns in the short direction of the building

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earthquake region. Also, vehicles parked near the buildings are damaged and people

nearby are injured just because of the collapse of gable walls.

5.7 Large and heavy overhangs

One of the most important mistakes observed is the existence of large and heavy overhangs over

the ground floors. This type of design is permitted by the existing public building code. However,

large and heavy overhangs without perimeter frames in the structures create problems when

subjected to the seismic loads. Perimeter columns were not connected by beams for architectural

concerns. This design approach created a case in which perimeter frames were not formed. Thus,

large and heavy overhangs caused bad damages in the structure. Moreover, large and heavy

overhangs will behave as cantilever beam under the additional forces due to the vertical com-

ponent of the seismic load. Also, the center of stiffness and center of mass will not coincide

because of these overhangs. Thus, earthquake forces applied to the center of mass will create extra

moments. Damages related to the existence of large and heavy overhangs are given in Fig. 24.

6 Structural failures of the masonry structures

The buildings in rural areas were built as masonry structures, which are made of stone,

brick and adobe materials. The reason of choosing such construction materials is that they

are easily available and they are more economical when compared with reinforced con-

crete. Tough climate in the region makes these materials desirable because these materials

are naturally insulated material which keeps the structure warm in winter and cool in

summer. Pumice concrete blocks (briquettes) are also commonly used in the region

(Fig. 25). The strength of masonry often depends on the bond between brick and mortar.

This bond is often very poor when cement mortars or clay-mud mortars are used.

Another widely used material in masonry structure is stone in the region. The binder

used in such structures is low-strength cement mortar or clay. Poor quality of this binder is

one of the reasons for the structural damages (Fig. 26).

Among the masonry buildings, the most damaged ones were adobe structures (Fig. 27).

Adobe construction elements are produced as a mixture of clay-mud-straw in 10–30 cm

dimension in the earthquake-affected region.

Fig. 21 Plastic hinges at all column ends in the long direction of the building

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The roof of adobe structures is built by tree trunks which are covered with 25–30 cm

thickness of soil layer. Due to atmospheric condition in time, degradation both in material

and in connections can be observed. Furthermore, heavy roof floor supported by these

materials can cause shear failures in the walls. Also, connection between walls and roof

Fig. 22 Damages due to strong beam–weak column behavior

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Fig. 23 Damaged gable walls

Fig. 24 Damages on the large and heavy overhangs

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were not observed in most structures. Thus, due to all these reasons, damage pattern in the

structural walls was inspected as the out-of-plane failure (Fig. 28). According to the

Turkish Earthquake Resistant Design Code (2007), reinforced concrete horizontal bond

beams shall be provided at places where slabs are supported by walls, such that they shall

be cast monolithically with the slabs (TEC 2007 section 5.5.2). However, horizontal bond

beams were not used in destructed masonry buildings.

Damages on the walls are also caused by large window openings (Fig. 29). Most of the

masonry walls are constructed by using sand–cement mortar as a binder. However, in

villages, clay-mud mortar is widely used instead. These buildings were commonly

Fig. 25 Structures with briquette wall and its damages

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constructed by their own residents without any engineering knowledge. These kinds of

damages were observed in the Topaktas, Tevekli, Mollakasim and Alakoy villages.

Historical buildings also faced damages in the earthquake. A good example for this type

of damage can be seen when the pre- and post-earthquake pictures of historical tomb is

examined (Fig. 30). For instance, crack lengths are increased and separations between

stones are observed in 7.5-m height Kadem Pasa Hatun Tomb which was built in 1,458

with cutting stone technique.

Fig. 26 Damages in the stone structure

Fig. 27 Example of adobe wall damages; diagonal shear cracking, failure of corner and collapse of out-of-plane

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7 Conclusion

Making scientific observations just after earthquake is devastating. Searching the damages

and failures for possible evidence of insufficient design code and academic knowledge was

really hard. As mentioned in the above sections, reason for such damages and failures was

not surprising according to up-to-date academic knowledge and current national design

Fig. 28 Examples of openings-and out-of-plane between the structural walls

Fig. 29 Structural wall damages caused by large window openings

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code. Thus, both structural and non-structural problems observed in post-earthquake site

visit can be summarized as follows:

• Earthquake spectra calculated with the records obtained from the near site station are

well below the design spectra given in the national code. Designers of the damaged

structures either did not consider the design code or constructers did not construct the

structures as designed.

• Some part of Ercis district do have gravel liquefaction problem. Since this part of Ercis

is not well populated, damages in the structures and casualties are not severe.

• Failures in reinforce concrete structures can be grouped as

• Poor material quality,

• Poor and uninspected labor,

• Reinforcement detailing unlike the ones mentioned in the design code,

• Not considering soft story action in the design phase,

• Missing out shear walls when designing ribbed slabs,

• Not avoiding strong beam–weak column connections,

• Unconfined gable walls, large and heavy overhangs caused damages to the buildings,

but they caused more economical damages by falling onto the cars which are parked

nearby.

• Masonry structures which are mostly located in rural areas faced damages due to poor

connections and poor material quality.

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Fig. 30 Pre- and post-earthquake condition of the historical tom

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