Re-thinking Marmara and 17 August Earthquake on Its Anniversary
Aug 17, 2016

20 years ago today, on August 17, 1999, at 03:02, a natural disaster struck northwest Turkey. With the 7.4-magnitude Marmara Earthquake that lasted 45 seconds and resulted in major loss of lives and property, we all had to confront the reality of earthquake hazards in Turkey. After that unfortunate night when we lost ten thousands of lives, as a society living on a quake belt, we tried to be more aware of earthquakes and various research institutions, universities in particular, accelerated their research activities in this field.

It was the North Anatolian Fault Line that triggered 17 August Earthquake, and ITU has been the major contributor from Turkey to the research efforts focusing on North Anatolian Fault Line’s remaining seismic gap under the Marmara Sea. For an evaluation of the current state of the earthquake research that has been carried out for the past 17 years and the extent of measures taken against the earthquake – whether or not Turkey as a country is prepared for a possible earthquake-, we interviewed our professors who have been actively involved in both the research on the Marmara Sea since 1999 and almost all the international projects on the issue. Interviews that will provide important insights into the earthquake reality of our country were conducted with Prof. Â. M. Celal Şengör of the Eurasia Institute of Earth Sciences and Department of Geological Engineering; professors from the Department of Geological Engineering such as Prof. Namık Çağatay, Prof. Ziyadin Çakır, and Assist. Prof. Gülsen Uçarkuş; and Assoc. Prof. Sinan Özeren of ITU Eurasia Institute of Earth Sciences

17 years have passed after 17 August 1999 Earthquake. What is the current situation of earthquake research after 17 years?

Prof. Â. M. Celal Şengör:
After the 1999 Earthquakes that cost the lives of many Turkish citizens and the properties of even more, we have witnessed a surge of interest worldwide in the Marmara Sea, and all of a sudden it has become the most extensively known inner sea throughout the world. As an Arabic proverb says, “No great work is possible without shedding tears.” Sadly, this is true for the geological research carried out on Marmara Sea since the year 2000. Among the Turkish institutions, Istanbul Technical University has assumed the greatest responsibility in these studies in which various institutions from many countries participated. Most of these studies were initiated and coordinated by ITU. Drawing on the findings of these studies, Kandilli Observatory and Earthquake Research Institute coordinated the work that aimed to increase the disaster preparedness of the city. The coordinated work between these two institutions should serve as an example to similar large-scale projects.

The major finding of the studies was that one or two disastrous earthquakes in Istanbul are imminent within the next few decades. If a single earthquake is to occur, the magnitude it can reach at most is 7.6. This means that its intensity in coastal lines can be as high as 10. Two different scenarios exist for two possible earthquakes. One is that both earthquakes can occur in a lateral motion. This is a weaker probability though. Another scenario involves a large, uniform, lateral motion with a magnitude of 7.6 followed by a rupture of the normal faults in the south of Cinarcik basin, resulting in a 7-magnitude earthquake. Such an earthquake would impact inner areas of Istanbul as well, just like what happened in 1894.

In any case, earthquake(s) will affect the coastal districts of Istanbul the most. Studies show that a major fault exists in the north of Çınarcık basin. An earthquake can happen as a result of a rupture in this fault.

Another hazard is ground displacements that could be facilitated by an earthquake under the Marmara Sea. These displacements can trigger tsunami. A study scrutinizing Yesilköy has shown that the height of tsunami on the shoreline can reach up to 7 meters.

Prof. Dr. Namık Çağatay: Following the 1999 Earthquake, various EU funded projects on Marmara Sea were carried out under the leadership of ITU. The most important of them are ESONET NoE (European Seafloor Observatory Network, Network of Excellence), EMSO (European Multidisciplinary Seafloor and Water-column Observatory), MARNAUT, and MARSITE projects. The aim of these projects broadly is to assess the earthquake risk in the Marmara Sea, mapping the faults, and exploring the past and present activities of various types of faults. The ultimate goal is to establish seafloor observatories that would enable long-term, multidisciplinary observations in order to observe the fault movements and research the relationship between earthquakes and the composition and amount of gases and hydrates.

Recently, in the EMCOL Research Centre at ITU, a project supported by Turkish National Geodesy and Geophysics Union researched and dated the sedimentary properties of turbidities in the Marmara Sea and their association with past earthquakes. This study yielded crucial insights into the activities of various faults on the seafloor over time; in other words, the prospect of them facilitating an earthquake.

Istanbulites are disquieted by even small-scale and medium-scale earthquakes in the Marmara Sea. Can these earthquakes be a sign of the expected Marmara Earthquake?

Prof. Ziyadin Çakır: Such small-scale earthquakes can happen at any spot in the Marmara Region, where the North Anatolian Fault Line extends over a large area. For this reason there is no scientific ground in claiming that such small occasional earthquakes could be the foreshocks of the expected big Marmara Earthquake. Increasing seismic activity in a small area can possibly be a foreshock, but such activities tend to be short lived and disappear without triggering a major earthquake. Hence, it is not possible to tell before an earthquake if these are foreshocks or not. It is a scientific fact that a large earthquake will happen in the Marmara Sea. However, no scientific prediction exists as to when it will hit although each passing day means an increased probability of earthquake.

We know that various international projects about earthquakes have been carried out in the Marmara Sea in the past 10 years. Could you inform us a little about the recent projects?

Prof. Ziyadin Çakır: The aim of the ongoing MARSITE project is to bring together scholars of different disciplines and coordinate the monitoring of various earthquake-related activities in the Marmara Sea and its surrounding. The project is coordinated by Bogaziçi University, and ITU is a project partner. Our chief responsibility as ITU is to re-assess the seismology and tectonics of Marmara Region in the light of new data and observations. To this aim, a database that contained information on active faults and researches in Marmara Region was created. Historical earthquakes that occurred in the past two thousand years are now being re-assessed in order to better our understanding of earthquake risk in Marmara Region.

Assoc. Prof. Sinan Özeren: In addition to the work carried out by Japanese scientists, a crucial contribution in MARSITE project was the establishment of seafloor observatories for the first time in the Marmara Sea, which will enable off-shore measurement of the fault activities. With satellite measurements in GPS-related work, it was already possible to monitor the activities of the North Anatolian Fault Line in the land. However, we lacked the measurements for the parts of this fault line that ran across under the sea. No study in the Mediterranean Sea has so far dealt with this issue, and it is being carried out in the Marmara Sea for the first time. Findings of this study will enable us to make direct measurements related to the activities of the North Anatolian Fault Line.

Gas-seepages in the Marmara Sea have recently attracted popular attention. Could you inform us a little bit about the issue?

Assoc. Prof. Sinan Özeren: We conducted the most comprehensive study on gas-seepages at the seafloor with our French partners during the MARNAUT Cruise in 2007. During the dives carried out by the submarine ship NAUTILE, in which ITU professors also participated, we observed the gas bubbles. We observed that it was predominantly biogenic gases that seeped along with fresh water (since Marmara Sea used to be a lake twelve thousand years ago, it has fresh water at the bottom levels). It would be wrong to associate gas-seepages with earthquakes, but it could be linked to the state of the fault at that moment. Seepages might have increased due to the increasing tension in the faults below the sea in the aftermath of the 1999 Earthquake. In other words, tension might have arisen in response to the structural changes in the area.

Have we learned to live with earthquake?

Assist. Prof. Gülsen Uçarkuş: It seems that we have not. The public should stop being preoccupied with questions such as “Is an earthquake going to hit?”, “When is that going to happen?”. Turkey is located on an active fault belt, which means that small-scale and medium-scale earthquakes can happen any time in this zone, and we have to learn to live with this reality. Many other countries on active fault lines such as the USA, Japan, China, New Zealand, and Chile are also living with earthquake risk.

I think media has a crucial role in this respect, and its mission should be to provide the public with correct information. One thing that could be done is to consult the experts on issues related to earthquakes and avoid featuring ungrounded discussions and opinions. For instance, the disinformation during post-1999 earthquake period showed us that public opinion can be easily manipulated via the media. Scholars also have a crucial role in that they should take into consideration the public sensibility while giving interviews.

In the past decade about fifteen large-scale international projects have been carried out in the Marmara Sea, which made it possible to gather highly sophisticated data sets. Various crucial implementations related to earth sciences have been executed; some of these are manned and unmanned dives in the Marmara Sea, obtaining high resolution bathymetric and seismic reflection data, and withdrawing sediment carrot in order to assess the records from previous earthquakes. These data sets enabled us to uncover various unrevealed facts related to the North Anatolian Fault Line and resulted in tens of graduate theses and hundreds of scientific publications. In this regard, Sea of Marmara has become an international laboratory, and we keep producing information related to the issue.