THE IZMIT earthquake

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I Z M I T
earthquake
I Z M I T
T H E
FINDINGS OF THE AIR POST-DISASTER
FIELD INVESTIGATION TEAM
AUGUST
17,
1999
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Results of inadequate detailing. Adapazari, Turkey
“This event presents a unique opportunity to collect and
synthesize detailed information, not only on seismic hazard
in Turkey, but on other parts of the world as well. While we
obviously cannot prevent earthquakes from occurring, the hope
is that we can apply the lessons learned from them to mitigate
their effects and, in the end, to save lives.”
Karen Clark
AIR President
“The most common types of structural failure observed
in Turkey were the result of poor quality materials, lack of
proper detailing, and failure to build to seismic code. Lack of
regulatory oversight and quality control mechanisms have been
major contributors to the magnitude of this disaster.”
Dr. Nozar G. Kishi
AIR Manager of Engineering Research
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Introduction
Introduction
• Investigate characteristics of building damage, including
On August 17, 1999,
at 3:02 a.m. local time, a major earthquake struck near
— major mechanisms of structural failure
— distribution of damage
the industrial city of Izmit, Turkey. The quake, which lasted about 45 seconds, measured 7.4 on the moment
The team consisted of both AIR professional staff and
magnitude scale. Sunrise brought with it scenes of dev-
local experts. Dr. Mohammad Zolfaghari, earthquake
astation from as far away as Istanbul, some 100 km to
engineer and engineering seismologist in AIR’s London
the west of the epicenter, and Duzce, 100 km to the
office, led the on-site investigation and was joined by Dr.
east. More than 15,000 people died. Over 300,000
Ian Nunez, senior structural engineer, also out of the
were left homeless. Over 75,000 housing units were
London office. Dr. Kemal Beyen, earthquake engineer
collapsed or heavily damaged. The total economic loss
and researcher at the Kandilli Observatory and
is estimated to be between $20-40 billion.
Earthquake Research Institute in Istanbul, provided local
expertise, as did Hafez Keypour, senior research
On August 20, just three days after the event, the AIR
engineer. Dr. Ugur Kadakal, AIR structural engineer
post-disaster field investigation team began an on-site
and citizen of Turkey, coordinated the effort out of the
survey of the damage. Their objectives were twofold:
Boston headquarters.
• Investigate the seismological and geological aspects of
the Izmit earthquake, including
— geophysical characteristics of the event
— geographical distribution of seismic-related hazard
— geographical extent of the affected area
Distribution of damage in the areas affected by the Izmit earthquake.
Over 75,000 housing units were collapsed or heavily damaged,
leaving more than 300,000 people homeless.
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C o l l a p s e d
b u i l d i n g s .
Adapazari, Turkey.
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Seismicity in Turkey
Earthquakes are a relatively common occurrence in
strike-slip faults. That is, as you face the fault from either
Turkey. Since 1900, an average of about 12 earthquakes
side, the side opposite is moving laterally to your right.
of magnitude 5.0 and greater have occurred there every
Both faults are roughly 1,000 km in length and have
year. Events of magnitude 6.0 and greater have
similar slip rates.
occurred, in the same time period, at a rate close
to one per year. The explanation for Turkey’s seismicity lies in the tectonics of the region.
Turkey lies at the juncture of three of the world’s
major tectonic plates. The Eurasian plate, to the
north, is a relatively stable plate, exhibiting little
movement. The African and Arabian plates are
moving north. These three giants are squeezing
the minor Turkish plate, which is wedged between
them, to the west. One of two faults that dominate
seismicity in Turkey, and the one that produced
Since 1939, major earthquakes in Turkey have occurred sequentially
from east to west. Many scientists believe that Istanbul is at risk from
the next big one.
the Izmit earthquake, is the North Anatolian Fault
(NAF). In many important respects, it bears a striking
resemblance to the San Andreas Fault (SAF) in California.
A major difference between the NAF and the SAF, how-
Both lie along plate boundaries. Both are right lateral
ever, is their tendency to produce major earthquakes.
Since 1900, the San Andreas Fault
has produced only two major
(M ≥ 7.0) events: the San Francisco
earthquake in 1906 and the magnitude 7.1 Loma Prieta earthquake
in 1989. In the same period, the
North Anatolian Fault has produced
eight earthquakes of magnitude
7.0 and greater, thus making it an
ideal laboratory for scientists and
engineers to study ground motion
and its effect on structures — and
perhaps to draw lessons that are
transferable to California and
elsewhere.
Seismicity in Turkey is governed by the convergence of three major tectonic plates.
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R e d u c e d
t o
r u b b l e .
Golcuk, Turkey.
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The Izmit Earthquake
The earthquake that occurred in the early morning hours
of August 17 caused surface faulting that extended 110
km. Evidence suggests that the actual rupture continued
underwater 50 to 60 km west of Golcuk, which
would mean that the total rupture length was
about 160 to 170 km. The earthquake originated at a depth of 17 km and caused right-lateral
displacement of over four meters in places, with
an average displacement of about three meters.
Surface faulting destroyed hundreds of buildings, cut through roads and pipelines, and
collapsed one bridge.
A major contributor to the enormity of the losses that resulted from the Izmit earthquake was
its location. The quake cut through seven heavily populated provinces. Indeed, these seven
provinces, which account for just 6.5% of
Turkey’s total land area, are home to over 15
million people, or 23% of Turkey’s population.
The seven provinces affected by the earthquake are among Turkey’s
most populous.
They account for 20.3% of Turkey’s building
stock and 35% of its gross domestic product, or GDP.
Most of the damage resulted from ground shaking. Other
The concentration here of people, houses and industrial
hazards were evident, however, and scattered across the
facilities guaranteed that losses would be significant.
affected area were instances of damage from surface
faulting, liquefaction, landslide, fire
following, and even flooding. The
AIR post-disaster field investigation
team set out on a systematic
survey of the effects of this earthquake, both geotechnical and
structural.
Map showing distribution of
hazard in the area affected by
the Izmit earthquake. While
most damage resulted from
ground shaking, there were
also instances of damage from
surface faulting, liquefaction,
landslide, and fire following.
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Surface Faulting
The Izmit earthquake caused as much as 110 km of surface
faulting, which tore through buildings, port facilities, and highways. The rupture primarily caused lateral displacement,
although in areas around Golcuk, AIR seismologists observed
vertical displacement of up to two meters.
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AIR Survey Methodology
The AIR field investigation team spent more than two
made of the overall architectural plan of each building,
weeks in Turkey following the August 17 earthquake, col-
the structural system, number of stories, level of dam-
lecting data and documenting damage. They visited two
age, and failure mechanism as judged by AIR structural
hundred locations spread throughout the affected area
engineers. Of almost equal importance, however, was to
and conducted systematic block surveys using sophisti-
note what did not fail and to determine what common
cated statistical sampling techniques.
structural characteristics the undamaged buildings
shared, if any.
At each location, the team mapped a grid overlay. A single city block was randomly selected from each grid cell.
At the end of each day, data and photos collected from
For each selected city block, the team surveyed every
these block surveys were transmitted electronically back
building within the block and collected data on the
to Boston for analysis and eventual incorporation into
geological characteristics at the site as well. Note was
damage curves.
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Over 200 locations were surveyed across the affected area.
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Izmit
Korfez
Kosekoy
Golcuk
Block surveys were performed in over 200 locations across the
affected area. At each location, blocks were selected randomly.
For each building within
the block, the team collected data on a wide
variety of structural characteristics — including
construction type, number of stories, structural
system, as well as on the
failure mechanism and
overall level of damage.
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The Team’s Findings
A striking feature of the built landscape in Turkey is the
relative uniformity of construction type. One underlying
reason for this uniformity has, at its root, Turkish eco-
practices were often shoddy and building materials often
nomic policy of the early 1980s.
of poor quality. Since 1975, Turkey has had quite good
seismic code, incorporating ductile design principles.
In 1981, the government of Turkey made the decision to
Relatively little effort has been made, however, to comply
open the economy, and the country underwent a trans-
with code and enforcement has been lax.
formation from an insular, state-run economy to one
open to trade and investment. The benefits have been
considerable. Real GNP has grown an average of 4.8 %
Building Characteristics
annually since 1981, the highest growth rate of any
The typical building in urban Turkey is five or six stories
OECD country. During this period, Turkey experienced a
tall and of reinforced concrete construction. The unifor-
huge migration from rural to urban areas, leading to a
mity of building height is not accidental. Land prices in
major building boom. This has several implications. One
the cities are high while labor, particularly unskilled labor,
is that much of the housing stock in Turkish cities is of
is cheap. In order to maximize the return on a construc-
roughly the same generation, of similar construction type
tion project, therefore, the tendency is to build up rather
and architectural plan, and built using similar construc-
than out, that is, to increase the number of stories. On
tion practices.
the other hand, local regulations dictate that buildings
with more than five or six stories (depending on the
Another consequence of the mass migration to urban
locale) must also be equipped with an elevator. Elevators
centers was that, because demand for housing was so
and their installation are very expensive. Thus we see
urgent, apartment
a clustering
blocks were put up
35%
very quickly. In the
30%
rush to complete pro-
25%
jects, construction
20%
Typical Building
Height
of
building
height around
five
and
six
stories.
15%
10%
05%
0%
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Number of Floors
Most buildings in the affected areas were between five and six stories tall.
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