By Anadolu Agency
February 23, 2023 5:35 amISTANBUL
Academicians from Istanbul Technical University (ITU) have published a preliminary investigation report on the Feb. 6 twin earthquakes, the epicenters of which were in Pazarcik and Elbistan districts of southern Kahramanmaras province.
In the preface of the report, which was released to the public Wednesday and shared with a written statement from ITU, the university’s rector, Prof. Ismail Koyuncu, noted that immediately after the earthquakes, experts from ITU in fields such as civil engineering, geological engineering, geophysical engineering and architecture carried out investigations and observations in the cities in the region in teams.
Noting that the experts who completed the first detection studies in the earthquake area prepared a preliminary report, Koyuncu said: “This report, which analyzes the (initial) earthquake in the region and examines the fault activity, is a ‘preliminary detection report’. It will also be shared with the public in the next few days.”
There were five main parts to the report, titled “Geological, geophysical, geodesical and geomorphological preliminary determinations of the earthquake” — “Evaluation of strong ground motions,” “Evaluation of structural damage,” “Evaluation of future projections, urban planning and construction techniques that can be used to meet the need for rapid housing,” “Environmental infrastructure” and “Evaluation in terms of earthquake waste management.”
The report recalled that the two earthquakes of magnitude 7.8 and 7.7 occurred at 4.17 a.m. and 1.24 p.m. and their epicenters were Pazarcik and Elbistan, respectively.
“The result of these earthquakes was mapped in satellite images over a wide area. Surface rupture is observed in certain sections. Although the tabular structure and trace of the fault are close to the known lines in the field, it is morphologically seen to progress from the ridges and slopes of the Cardak fault,” the report said.
“The terrain traces and surface fracture map of this earthquake contain brand new information. Slip distribution of interrelated segments in the region suggests that the Amanos segment was broken simultaneously by two independent earthquakes, the Cardak fault by two, the Pazarcik segment by one, and the Golbasi segment by one. Another remarkable factor is that the active fault map of Türkiye and the surface fractures do not overlap each other and pass through different areas,” the report added.
In the report, it was stated that the instrumental moment magnitudes of the Feb. 6 Nurdagi-Pazarcik and Ekinozu earthquakes were calculated as being of magnitude 7.8 and 7.7 respectively, with the joint inversion of far and near field seismological (BB and SGM) and geodetic (GPS) data and observations.
In the statement, it was noted that the rupture-slip models based on the multi-dataset gave displacement values of approximately 8-10 meters on more than one fault segment for both earthquakes and was consistent with field observations.
According to the static evaluation, the greatest horizontal displacement after both earthquakes was 4.7 meters at Ekinozu station, while the horizontal displacement values at Malatya, Gaziantep and Osmaniye stations were 69.9, 39.6 and 29.2 centimeters, respectively. In the report, it was emphasized that the results obtained from the kinematic evaluations generally supported the static evaluation results.
In the report, it was also pointed out that reliable data could not be obtained from some stations due to the damage during the earthquake of the accelerometers and the buildings they were placed in, and it was noted that the spectral acceleration, velocity and displacement magnitudes calculated using the acceleration records downloaded from the Türkiye Acceleration Database and Analysis System site of Türkiye’s Disaster and Emergency Management Presidency (AFAD) on Feb. 9 were presented.
Most obvious causes of destruction
Reminding that many reinforced concrete buildings in 10 provinces on the East Anatolian Fault Line collapsed and turned into debris in the severe earthquakes of 7.8 and 7.7 magnitudes respectively in Pazarcik and Elbistan districts of Kahramanmaras, the report added that although “many parameters are effective in the destruction of the collapsed buildings, the age of the buildings, the low bearing capacity of the floors on which the foundations are placed, the quality of the materials used in the construction, the cross-section dimensions of the columns and beams and the amount of reinforcement, and the lack of structural system elements in accordance with the regulations in force during the years they were built” were the most obvious reasons for demolition in addition to other construction defects and the different floor levels of the buildings built in the adjacent order.
“In Kahramanmaras and Adiyaman, it has been observed that the first floors of the majority of the buildings in ruins either completely or partially became a floor mechanism and (led to the) collapse of all floors on top of each other,” the report added.
“In regions such as Hatay-Antakya and Adiyaman-Golbasi, it has also been observed that the buildings collapsed in an oblique position by sinking into the ground due to the soil liquefaction effect, or either the whole of the building leaned on its side or sank into the partially liquefied ground,” said the report.
“As a result of these earthquakes, hospitals and some public buildings which were built in accordance with the projects of all structures, such as reinforced concrete buildings, in areas with high ground capacity in accordance with the regulations, have shown once again that the structural damage that may occur in buildings as a result of such severe earthquakes can be very limited,” the report further underlined.
Possible construction techniques evaluated
The report, which evaluated the pre- and post-earthquake states of the region which was affected by earthquakes and where 13.5 million people lived, also said: “Regulations that legalize unhealthy and unsafe building construction, such as zoning amnesty, which are not based on a scientific basis, should end. Natural thresholds should be taken as a basis in the reconstruction process, and construction in these areas should not be allowed except for cultural assets in the new planning process.”
In the report, it was further noted that in the houses to be built in the areas affected by the earthquakes regarding the restructuring process of the city, the advantages of the carrier systems built with tunnel formwork, prefabricated reinforced concrete houses and modular steel systems should be evaluated together, taking into account the ground conditions and many other similar conditions.
Environmental infrastructure and earthquake waste management discussed
In the report, which pointed to the damaged infrastructure as well as superstructures, it was noted that there could be acute problems in water supply and waste water removal, especially with damage to network and sewerage pipelines.
For this reason, it was stated in the report that the risk of infectious diseases with a high potential for transmission through water increased after the earthquake and that it is vital to take technical measures for safe water supply quickly in order to prevent water-borne epidemics.
Estimated waste amount calculated
In the report, it was stated that as of Feb. 16, 263,800 independent units in 61,722 buildings within the scope of damage assessment studies carried out in 13 provinces by the Ministry of Environment, Urbanization and Climate Change after the earthquakes were heavily damaged and demolished, requiring urgent demolition.
According to this, preliminary calculations of the amount of earthquake waste were made and the estimated amount of waste to be generated on a provincial basis was calculated in the report.
“The total amount of earthquake waste is predicted to be between 50 million tons and 110 million tons. The provinces where earthquake waste is expected to be the most are Hatay, Kahramanmaras, Malatya, Gaziantep and Adiyaman, which were the most affected by the earthquakes,” the report said.
“The need for landfills is at the highest level. In this respect, the remaining capacity of the existing fields should be determined primarily and new temporary and final storage areas should be determined if necessary. These provinces are followed by Osmaniye, Diyarbakir and Elazig, according to the amount of waste generated. For Adana, Kayseri, Kilis, Nigde and Saniıurfa, due to the relatively low amount of earthquake waste, it is thought that the existing sites may be sufficient. However, control of the current field capacities is still required.”
In the report, it was emphasized that necessary occupational health and safety measures should be taken during the demolition of buildings and transportation and management of waste.
“Earthquake wastes should be transported to temporary storage areas, the materials in the wastes should be separated and largely reused, recycled or recovered, and the remaining wastes should be disposed of within the framework of the provisions specified in the relevant regulations according to the level of danger,” the report said.
“Temporary and final storage areas should have the capacity to meet the amount of waste. The entrance of unauthorized persons to the areas should be limited. Due to the risk of fire, waste should not be stacked above a certain height, especially in temporary storage areas. Necessary security measures should be taken for situations such as fire risk,” it added.
The report also noted that studies should be carried out in the short, medium and long terms in order to observe and repair the social effects of the earthquake.
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