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9. Establishment of the Integrated Seismic Observation System around Istanbul and the Marmara Region


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9.Establishment of the Integrated Seismic Observation System around Istanbul and the Marmara Region

9.1.Purpose, Necessity and Tectonic Background < TC "Purpose, Background and Necessity of the System">

9.1.1.Purpose and Necessity


Reducing earthquake hazards and preparation against disasters require precise and detailed information of earthquakes, education and response. Due to insufficient network coverage and number of seismic stations in and around Istanbul and Marmara Region, the present status of stress levels and earthquake hazard potential can not be determined. In order to obtain precise determination of hypocenters of seismic events and to increase the number of well determined focal mechanisms the number of seismic stations should be increased. The well determined hypocenters will provide very crucial information about various topics in earthquake process, focal mechanism solution, attenuation property of the seismic waves and seismicity. The well located hypocenters provide a vital data base for scientific research. For instance, the collection of focal mechanism can be interpreted in terms of average stress tensor acting in the region. This information together with other seismological, geophysical and geological observations (GPS, seismic refractions, neotectonics, etc), contribute to a better understanding of the mechanisms of deformation, to the identification of seismic gaps in detail along main faults and to correct evaluation of seismic hazard in the Marmara Region and Istanbul. Precise seismic data is essential in order to conduct micro regionalization, attenuation properties of the crust, creating more real scenario earthquakes and city planning studies. Main aim of the monitoring earthquake activity continuously for a region is to get precise information about how and in which depth they are occurring. The distribution of hypocenters and source mechanisms of earthquakes are essential to understand what is going on under ground. Also scientists can get lots of information about the structure of the Earth’s crust by using seismic waves generated by these earthquakes. Whenever scientists need to say something about seismic activity and seismic risk of a region it is necessary to have a complete and good quality digital data set.

Precise earthquake location of micro earthquake data is also essential to understand seismicity patterns of a region and therefore seismicity patterns such as clustering and quiescence should be monitored in detail for a better understanding of forecasting of a strong earthquake. Recent studies showed that there are two notable locations of high seismic activity in the Marmara Sea. The eastern one is just after the 17 Aug. 1999 Izmit earthquake and it is concluded that this activity was triggered by the Izmit earthquake. However, in view of clustering activity in the epicentral area of the Izmit earthquake some decades before the mainshock, seismologists should carefully monitor this activity in relation to a future large earthquake nearby Istanbul in the Marmara Sea region. A high seismicity area is also seen in the west of the Marmara Sea. This area is located in the eastern extension of the 1912 earthquake of M7.4. This activity should also be carefully monitored. In the area between these two high seismicity areas, seismicity is rather low. In the western part of the North Anatolian Fault Zone, two seismic networks have been in operation; they are MARNET surrounding the Marmara Sea and IZINET in the east of the Marmara Sea. Due to insufficient seismic stations and not enough digital data availability of permanent networks the data quality was not so high and this data can not be used for solving seismological and earthquake engineering problems of Istanbul. By increasing the number of seismic stations in the Marmara Region and combining all available online (real-time leased line and radio-link seismic stations) seismic station in one integrated system has a lot of advantages in real time seismology. In this project, the main idea was to increase the number of seismic stations in the vicinity of Istanbul with the financial support of JICA, increase of seismic stations around Istanbul and Marmara Region with equipments from local resources. In view of high potential of large earthquake occurrence in this area, the system is extremely important for monitoring of seismic activity. The second idea is to collect all available data in the same hardware, software and format so seismologist can use automatic location by using computers and display results in a graphical environment through internet very quickly.

This project will also help to collaborate with scientists from Istanbul Municipality and other scientific communities in Turkey. This new system will provide digital and complete data sets for earthquakes for Istanbul and the Marmara Sea region and these data sets will be available to the scientific community to conduct detailed research in seismology and earthquake engineering.

In this project following scientists have been worked:

Serif BARIS, Project Coordinator

Assoc. Prof., Department of Geophysics, Kandilli Observatory and Earthquake Research Institute, Bogazici University, Turkey.

Yoshimori HONKURA

Prof., Earth and Planetary Sciences Department, Tokyo Institute of Technology-Tokyo, Japan

Akihiko ITO

Assoc. Prof., Utsunomiya University, Japan

S. Balamir UCER

Prof., Dept. of Geophysics, B.U. Kandilli Observatory and E.R.Inst.

Nafiz KAFADAR

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Dogan KALAFAT

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Yavuz GUNES

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Pinar DENIZ

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Feyza Nur BEKLER

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Alev BERBEROGLU

Seismological Obs., B.U. Kandilli Observatory and E.R.Inst.

Toshio KONO

Tohoku University, Japan

Mahmut BAS

Istanbul Metropolitan Municipality(IMM), Soil and Earthquake Research Department

Suleyman BUYUK

IMM Soil and Earthquake Res. Dept.

Kemal DURAN

IMM Soil and Earthquake Res. Dept.

Oner TAYMAZ

IMM Soil and Earthquake Res. Dept.

Enver SAYAROGLU

IMM Soil and Earthquake Res. Dept.


9.1.2.Tectonic Background in and around the Marmara Region


Northward motion of the Arabian plate relative to the Eurasian plate and the retreating subduction boundary along the South Aegean Trench result in westward motion of the Anatolian block (McKenzie, 1972). The right-lateral North Anatolian Fault (NAF) is the northern boundary of the Anatolian block. It extends more than 1400 km from east to west. The Marmara region, between Izmit and Dardanelles, belongs to the North Anatolian Fault system (NAF). The Marmara region is an active tectonic zone characterized by a transitional regime in between dextral strike-slip regime of the NAF to the east and the extension regime of the Aegean Sea to the west. Tectonics in this region is characterized by the splitting of the NAF into three branches running all which trend in an East-West direction (Figure 9.1 .1).

The rate of displacement of the Anatolian block with respect to Istanbul, as obtained from GPS observations of displacement (Barka and Reilinger, 1997), is around 2.4 cm/year in a WSW direction, a higher value then expected. The northern branch is the most active one, and this is most remarkable when the whole set of known historical earthquakes is taken into account. Many historical destructive earthquakes occurred in the Marmara Region causing major damage to Istanbul city (Genc and Mazak, 2001). Figure 9.1 .2 shows historical seismicity and fault ruptures of the Marmara Region for the last five centuries. The figure clearly shows that the unbroken segment of the NAF is located south part of Istanbul with an estimated length of 160 km. In addition detailed micro-earthquake studies show that the northern branch is more active than the other two branches (Baris et al., 2002).



Figure 9.1.1 Tectonic sketch of Turkey. NAF represents the North Anatolian Fault system and EAF represents the East Anatolian Fault System. Arrows indicate the direction of plate motions. The fixed Eurasian plate is located north of NAF (Woith, H., personal communication).



Figure 9.1.2 Historical seismicity of the last six centuries together with fault traces. Dashed lines show submarine proposed faults (Woith, H., personal communication).

The westward migration of a series of strong earthquakes which started with the Erzincan 1939 earthquake (estimated Mw between 8.0 and 8.3) ended with the 17 August 1999 Izmit earthquake with Mw 7.4. West of Izmit earthquake projecting into the Marmara Sea, there is an unruptured 160 km fault segment or in other words seismic gap. In the 20th century the NAF ruptured from eastern Turkey to Izmit Bay in a sequence of eight M>7 events, the Izmit and Duzce earthquakes (12 November 1999) being the most recent (Figure 9.1 .3). In the decades to come, it is likely that rupture of fault segments within the Marmara Sea Region will complete this sequence.

Figure 9.1.3 Migration of earthquakes sequence with M>7 along the NAF in the last century showing year and magnitude of event. Please note that there are unbroken segments (seismic gaps) in the Marmara Sea and east of Erzincan on the NAF. (Woith, H., personal communication).

Seismic risk in the Marmara Region is high due to the presence of several large cities (Bursa with a population of 2 million, Tekirdag with a population of 1 million, Izmit with a population of 2 million, Yalova with a population of 1 million, Balikesir and Canakkale with a population of 1 million and the largest Istanbul with a population of 12 million). An important percentage of Turkey’s industrial and communication facilities are also concentrated within the Marmara Region. Istanbul was the capital city of Byzantine and Ottoman Empire; therefore it has a lot of very important historical monuments, and cultural heritages. Istanbul is also rapidly growing city that has been heavily damaged by earthquakes twelve times during the past 15 centuries. The 1894 earthquake (with an estimated moment magnitude of 7.0) has been the last historical earthquake to affect Istanbul and its surroundings (Ambraseys and Finkel, 1987). Parson et al., 2000, studied the last 600 years of seismicity and calculated probability for a strong earthquake for Istanbul. According to whose study, seismic vulnerability of Istanbul is growing and there will be a strong earthquake with 62±15% probability within 30 years and 32±12% during the next decade. Figure 9.1 .4 and Figure 9.1 .5 summarize their results. As also pointed out in the same paper after the 17 Aug.1999 Izmit earthquakes, Coulomb stress has increased for the west of the rupture region (Figure 9.1 .6 and Figure 9.1 .7).

Figure 9.1.4 Location of large historical earthquakes since 1500. Blue dots indicate95% confidence bounds on epicenter from historical records. Green dashed contours give maximum length of ruptured areas due to earthquakes. Red hashed contours show the moment magnitude M needed to satisfy the observations for a given locations (Parson et al., 2000).



Figure 9.1.5 This figure shows calculated probability of an M≥7 earthquake (equivalent to MMI≥VIII shaking in greater Istanbul) as a function of time. The large but decaying probability increase is caused by the 17 August 1999 Izmit earthquake. Background tracks the probability from earthquake renewal; interaction includes renewal and stress transfer. Light blue curve gives the probability had the Izmit earthquake not occurred.



Figure 9.1.6 Stress changes after the 17 August 1999 Izmit earthquake for Istanbul. White circles show Izmit aftershock detected by IZINET (first 12 days). White rods indicate ruptured faults and yellow star denotes the mainshock. Grey solid lines represent unruptured faults in the region (Parson et al., 2000).



Figure 9.1.7 Coulomb stress calculation for co-seismic changes. Red regions show increasing stress regions. White and grey lines indicate faults and dots denote aftershocks of Izmit earthquake (Parson et al., 2000).


9.2.Existing Seismic Networks


Seismological Observatory of Kandilli Observatory and Earthquake Research Institute (KOERI), Bogazici University, is operating national seismic network in whole Turkey. In Marmara Region there are two seismic networks. The first one is called MARNET seismic network and the second one is called IZINET seismic network. The IZINET and MARNET networks are the first networks recorded two large events on the NAF with background seismicity and aftershocks in Turkey. These two networks have been operated with different hardware, software and technology up to March 2000. After the 1999 Izmit earthquake, Ito et al., 2002, installed the same data acquisition system for both networks. They were, however, still operated as an independent network to each other until this project was established.

9.2.1.MARNET Network


The MARNET network was installed in 1976 (Ucer et al., 1985) with nine single- component radio-telemetry stations around Marmara Sea and operated by Seismological Observatory. This network is operated continuously by the Seismological Observatory and it plays an important role in the national seismic network of Turkey. Before the 17 August 1999 Izmit earthquake the number of stations increased to 16 adding new leased line and radio-telemetry seismic stations. Since then the network size has been increased to 19 stations. The seismic signals has been centrally digitized since 1978 and recorded in digital form up to 1991. The digital recording was stopped in 1991 due to hardware failure. Digital recording of records earthquakes is started in 2000 again. Only the MARNET network has provided continuous seismic information for the Marmara region after its installation. Figure 9.2 .8 shows the present situation of seismicity in the Marmara Region. Note that the seismicity is diffuse due to insufficient station distribution and doesn’t show precise locations of earthquakes. Site selections of new stations are still continuing and new seismic stations will be installed in the near future.

Figure 9.2.8 Seismic activity of Marmara region for earthquakes magnitude is equal and larger than 3.0 for the period of 1900-2002. Seismic stations in Marmara Region operated after 1976 and therefore above seismicity map demonstrates dominantly seismic activity of last 25 years.


9.2.2.IZINET Network


The IZINET network was installed in August 1992 with six seismic stations in order to monitor the microearthquake activity and seismicity patterns around Iznik-Mekece fault in the south-eastern Marmara Region. It was installed east adjacent region where MARNET was covering. Due to increasing earthquake risk on the western extension of the NAF (Toksoz et al., 1979) the number of seismic stations increased to 16 before the Izmit earthquake so that it covered all three branches of the NAF in the studied region.

This network has one cable connection and 15 telemetric stations. The central station is located in Kiblepinar-Yenisehir-Bursa. This network was using 12 bit centralized A/D converter and recorded earthquakes in digital form by using IASPEI software (Baris et al., 1996, Baris et al., 2002). IZINET was the first attempt to install the PC based data acquisition system in the Marmara region and it provided the great contribution to us when two strong earthquakes occurred in 1999. However, the technology of data acquisition and analysis system has gotten old and we needed to change it into new system.

After having two strong earthquakes in and nearby the network, we have installed a new up-to-date hardware and software system for seismic data acquisition, named EQDAQ system, in both of IZINET and MARNET in March 2000. The new system can record earthquakes in digital form by using 16 bits A/D converter up to 32 channels. Thus, two systems can record earthquakes with the same data format and any seismologists in Kandilli can analyze data in the same format with the same analysis software.

In the year 2000, a fiber-optic communication system was installed between the base station of IZINET and Kandilli Observatory, Istanbul for getting data at any time. Currently, all data of triggered events at IZINET are coming to Istanbul within a couple of minutes after the occurrence of each event. When this fiber-optic backbone system was designed in Kandilli it is also planned to implement real-time data transferring in future. Therefore, this project needs a fast and high quality connection in order to realize the real-time data transferring. The structure is right now four 2 Gb/s capacity with six lines fiber optic cable for the new seismic stations proposed in this project. And the communication capability can be expanded very quickly if necessary by installing new devices and cards into the fiber optic system.

Since the IZINET has been installed more detailed seismic information and clearer clusters in the south-eastern part of the Marmara Region has been obtained. Seismic activity detected by the IZINET in the last seven years for the eastern Marmara region is given in Figure 9.2 .9 and Figure 9.2 .10. Figure 9.2 .9 shows earthquakes detected by the IZINET and MARNET. Figure 9.2 .10 displays only the IZINET stations’ locations. Note that there are five clustering regions observed in the eastern Marmara region and the 17 August 1999 Izmit earthquake occurred at the western tip of the Izmit cluster (region B in Figure 9.2 .9). This phenomenon may be an important pattern for the NAF and this type of seismic activity should be inspected carefully to understand the relation between clusters and future strong earthquake location.

Figure 9.2.9 Seismicity detected by IZINET and MARNET seismic networks for the eastern part of Marmara Sea Region for the period of 1993-16 Aug., 1999. Rectangular regions show clustering areas except region F which shows seismic quiescence. Please note that the 17 Aug, 1999 Izmit earthquake occurred on the western tip of the cluster in Region B.



Figure 9.2.10 Seismicity detected by IZINET for the eastern part of Marmara Region for the period of 1993-16 Aug, 1999. Earthquakes are plotted only by using IZINET stations and good quality solutions. Red star indicates mainshock of the 17 Aug., 1999 Izmit earthquake. Solid lines show proposed active faults.


9.2.3.Data Acquisition algorithm for MARNET and IZINET


The data acquisition system is computer based system and it has 16 bits Analog-to-Digital Converter (A/D). In the acquisition system it can be used 32 seismic channels up to 500 sample/seconds for each channel. Project members have two sets such acquisition system for IZINET and MARNET networks. In this system, acquisition software is running in Windows NT or Windows 2000 operating system in a solid state personal computer (PC) and time is collected by GPS receiver which synchronizes with the Central Processing Unit (CPU) time of the PC. The detection algorithm runs continuously and uses Short Term Average/ Long Term Average (STA/LTA) algorithm. Software is checking the signal level for each channel namely for each station and it compares with other channels. If predefined number of channel or more channels than this value (for instance 3 channels used in general) has some energy changes according to input parameters software is triggering this behavior as a seismic event and records into the hard disk. Acquisition PC has a large hard disk and this disk is divided into 3 partitions. In the first partition operating system and acquisition software is running. In the second part of the hard disk continuous data is recorded into the ring buffer, and triggered data is stored into the third partition. PC has two Ethernet card and two serial ports. These ports are used as a communication link between the A/D converter and the PC, and the base station of network is sending data by internet to the data center for automatic analysis. Acquisition system of ISTNET is based on WIN acquisition system and consists of two different PC with Linux operating system. All out stations sending digitized data trough leased line and receiving site has modems, router and hubs. The data coming in UDP packets and software is accessing data trough serial port and network port trough PC. The first PC is used for storage and analysis and second one is a mirror image of the first PC. Thus, this PC can be used either analysis or storage and backing up the acquisition. The team installed another PC which converts IZINET and MARNET data into WIN system and sending a server PC in the center. This server PC stores all data and has a sharing file system. Thus, any seismologist in Kandilli can access and use all combined data.

9.3.New Seismic Observation Network

9.3.1.Data acquisition


Figure 9.3 .11 shows present permanent seismic station distribution in the Marmara Region. These stations are operated continuously by Kandilli Observatory and Earthquake Research Institute (KOERI). Although the Scientific and Technical Research Council of Turkey (TUBITAK) is also operating seismic observations in the Marmara region, those stations are not permanent. In addition, Istanbul Municipality has deployed several seismic stations in and around Istanbul. However, those stations are offline stations and data is not available in real-time. This figure clearly indicates that seismic station coverage for Istanbul is very poor and researcher can not derive enough information about crustal properties by using data from the current network configuration. New seismic stations in and around Istanbul should be installed and operated continuously.

Figure 9.3.11 Online seismic stations running before installation of ISTNET stations in 2001 in Marmara Region. Most of the stations are single component and radio-link connections. Western part of Marmara Region and Istanbul city has not enough seismic stations.



Figure 9.3.12 This map shows all available seismic stations at present and planned seismic stations in 2003. Please note that Municipality stations are offline (not real time) seismic stations and data from these stations can not be used for real time seismology.

The project team installed six online 3-component seismic stations on March, 2002. The locations of those new seismic stations are shown in Figure 9.3 .12 with existing seismic stations and several planned stations for future. Location of those stations was selected by taking into account all fault segments, earthquake clusters and available seismic stations nearby Istanbul.

These seismic stations have a 3-component short period (L22, Mark Products) seismometer and data logger (LS7500, Hakusan Corporation) with GPS time correcting device. The Seismic signals are digitized at each station with 100 Hz sampling frequency and sent to Kandilli Observatory in digital form by using leased line connection to the Kandilli Observatory. The precision and dynamic range of the A/D converter is more than 20 bit. This new observation system provides us higher quality digital seismic signals compare to the existing seismic networks in the Marmara region.

The data sent to Kandilli Observatory are collected by a UNIX data acquisition system, named WIN system (Urabe, T, 1997), and recorded continuously in a hard disk. The computer is equipped 30 GB hard disk and capable to keep data for two weeks. While collecting the continuous data, the WIN system makes trigger files when it detects seismic events. This is a kind of smart technique. Even if the WIN system failed to trigger an event, seismologist can remake the trigger file for that event manually from the continuous recording data.

Another advantage of this system is the flexibility. Anyone can add new seismic stations very easily only by preparing another equipment and leased-line connection without any modification of hardware at the central station. .


9.3.2.Data Integration


At the moment the team installed the WIN system for ISTNET, the different data acquisition system, EQDAQ, were operated for MARNET and IZINET with different format of digital wave form data. Therefore, it is necessary to integrate every seismic data into one system. This was realized through the internet connection of computer network.

The server computer of the WIN system is always monitoring incoming data packet with UDP protocol from six ISTNET stations. This mechanism can be used for the real-time data integration. Only what is needed to establish the real-time data integration is to transform the seismic data in EQDAQ format to WIN format in real-time and to send it to the WIN server by using UDP protocol. In order to execute these jobs the project team installed in another FreeBSD computer on the LAN of Kandilli Observatory.

The data transmission for MARNET, therefore, is very easy, because the computer of MARNET data storage is on the same LAN on which the WIN server is working. For IZINET, the fiber optic telecommunication system mentioned in the previous section of this report is used. The team put a FreeBSD computer in the IZINET base station as well as for MARNET for the data transformation and data transmission. The FreeBSD computer is sending a UDP packet once in a second to the WIN server in Kandilli Observatory. The IZINET base station is connecting by the fiber optic cable both to Iznik Center and Istanbul Kandilli. Iznik center has another connection to Kandilli Observatory. Thus, the IZINET data is reaching to Istanbul Kandilli without any interruption as long as one of two routes of data is in operation. This provides us a kind of fail-safe system. The block diagram of present network system is shown in Figure 9.3 .13.

Now every digital seismic signals in WIN format at Kandilli Observatory in real-time can be obtained. This improves the accuracy of event detection significantly, because the integrated network has more than 40 seismic stations and is covering almost whole Marmara region. Furthermore, it makes every analysis easier compare to the previous situation.

New stations connected into this system and the right side of the Figure 9.3 .13 explains the structure of the telecommunication system used in this project. The upper part is present structure of the system and now it is used by the IZINET, MARNET and other online national seismic stations operated by Seismological Observatory.

Figure 9.3.13 Graphical sketch of telecommunication infrastructure of real time data for seismological online stations in Seismological Observatory, KOERI.


9.3.3.Data Analysis


At present project members have been using data analysis software is written by Dr. Ito from Utsunomiya University and WIN system by Dr. T. Urabe (1997) from Earthquake Research Institute of Tokyo University. Dr. Ito has been using these programs for many years and installed this software in March 2000. Since then project members are using it for data analysis. Both programs are user friendly and project members have trained in Turkey and in Japan in order to use it efficiently. Analysis software is written in C language and runs in Linux system. This software has also some other useful programs for data analysis and interpretation. Whenever acquisition software has detected and sent data into the analysis software it is also sending an e-mail to the user that a new event has arrived into the analysis system. The new system has automatic location software and this software automatically reads earthquake phases from each channel and makes hypocenter determination. It is also putting these results into an earthquake catalog. There is another software is written for updating the internet environment and web page of the epicenters maps routinely. In this project results of hypocenter locations are displaying by using web pages through the internet. Web software has capability of displaying epicenter maps of the earthquakes for different time scales, namely daily, weekly, monthly and yearly for web page display. So people can access and monitor recent seismic activity in and around Istanbul at any time at any place where internet is available. A private web server was proposed and bought already to realize this procedure for the project. When the number of channel is increased detection software will not provide expansion. This increment of seismic stations and combination of different networks can be realized by using the WIN system which is widely used by Japanese networks and agencies. By using this software can collect any number of seismic networks and there are no limitations of number of seismic stations. For example Disaster Prevention Research Institute of Kyoto University is using this system with 2,000 seismic stations and Sendai University is using it for almost 320 seismic stations. Soon, we will implement this software into our new detection system. Actually, WIN software was used to make analysis for the data collected by Nakamura et al. 2002, for the aftershock study of Izmit earthquake with project members in Turkey. The project members therefore have experience with the WIN system. Dr. Ito developed a new software and installed it into EQDAQ system of MARNET and IZINET. The software transmits the MARNET and IZINET data as UDP packets with the same format of WIN system in real time to the WIN server. Then, the WIN server will store all data from ISTNET, IZINET and MARNET networks in an integrated continuous form. WIN system has an automated hypocenter determination routine in it. So, any seismologist can realize the automated hypocenter determination system in WIN system. This new system has been implemented into the Seismological Observatory and project members and other seismologists are using it routinely. Thus, any seismologist can determine earthquake parameters within a few seconds and they can get final solution within a few minutes. Results can be seen in the web right after the final solution.

9.3.4.Data Base and Data Dissemination


At present the new system is running and all seismic data from IZINET and MARNET networks are stored in large capacity DAT and DLT tapes in continuous form and event trigger basis. Data storage combines raw data and earthquake data. These earthquake data are available for any scientific research. The new system has WIN format data but it has also data conversion software for widely used international formats such as SAC and SUDS. Now, the system store data in SAC format. If someone needs to convert data into different format they should do it by themselves. Earthquake catalog data is freely distributed and it can be accessible through the internet. The new system is using internet facilities widely for data distribution purposes. The computer systems designed for this purposes and data storage environment and security of the systems and data are taken into consideration seriously. The web server will act as an FTP and Web server as well. All of acquisition, storage and analysis PCs are located in a secure network environment. IP access is forbidden into these systems so no one can alter the data collection procedure. The project team put the web server behind a hardware firewall including proxy server and installed another software firewall to the server. Operating system is installed as Linux for security reasons and more advantageous for running as a server. In the server systems also RAID system is used so operating system will not stop due to hard disk failure. Thus, anyone can access to our web page without interruption. In the near future the project members in KOERI will install clusters of PCs into the server system so if access is very high due to intensive internet traffic or due to other moderate earthquakes in Marmara Sea the server can distribute surfing people on the project web page into clustering PCs. As similar web server will be located in the Municipality building as a mirror. So, data access will be more secure. The project members also are planning to connect second internet access this system. The structure of the networking is given in Figure 9.3 .14 and Figure 9.3 .15. Most of the acquisition PCs and analysis PCs are in the private network which means are closed to internet traffic due to security reasons.

Figure 9.3.14 Block diagram of new system in KOERI. Numerals indicate private network IP numbers used in this secure network system.



Figure 9.3.15 Block diagram of network diagram of IZINET network and connection to KOERI. Numerals indicate IP address of each device in the network. Please note that left lines on the routers carrying data signal to KOERI, Istanbul.

Due to some technical problems internet traffic is slow or even interrupted at Kandilli. Overcoming this problem it is necessary to install second internet line for this project and it will be available continuously. Necessary router and devices are already implemented into the communication infrastructure and in near future it will have extra internet connection. The second internet access will be at least 1 Gb/s capacity and will serve only for seismic data and web access. These two internet access locations will be used not for only distributing data and information but also will be used for training and education of people for disaster preparedness and mitigation.

In this project all available digital data from IZINET and MARNET is collected by computers and have installed one data acquisition hardware and software provided by KGC Company in Japan. This company has also changed their data format and data transfer routine for adaptation of WIN system and their system. The data process and automatic location program is written by Dr. A. Ito and project team was used up to August 2002. For collecting ISTNET digital data and combination of other available data sets the project group is using WIN system. WIN system has also automatic location and acquisition software. This system has also some other facilities in acquisition and analysis purposes such has mapping and focal mechanism solution programs. Seismologists are now using the WIN system in Kandilli Observatory using MARNET, IZINET and ISTNET data sets. In August 2002, WIN system is installed for data combination of different networks and processing. The WIN system is a very flexible system and many observatories in Japan have been using widely this system for ten years. After automatic location of the seismic events the results will be displayed through internet for daily, weekly and monthly seismic activity maps and as well as earthquake catalogs trough our Web Server. These maps will be displayed in the entrance of Istanbul Municipality Headquarter so people can monitor recent seismic activity continuously on the large screens. This will also increase the level of earthquake information of public.


9.4.Site Selection and Installation


New stations are able to send data by using leased telephone lines and they also have radio-link or fiber optic facilities provided by Turkish Telecom. Ordinary telephone lines are available on each village but they can not be used for data transmission for seismic studies. Unfortunately all villages do not have leased line facilities even in Istanbul. New sites were selected due to available leased line connection for telecommunication, considering good station coverage for the region, location of fault lines, earthquake clusters in land and in sea, high signal/noise ratio, easy access for installation and maintenance of seismic stations and bedrock properties of the sites in and around Istanbul. Site selection and information collection about telecommunication infrastructure providing online data transmission from the Turkish Telecom for the villages in Istanbul and the Marmara Region has been completed. As pointed out above, Figure 9.3 .12 shows the distribution of all available sites and proposed station locations for ISTNET, IZINET and MARNET stations. This project is not at the final stage for installing new seismic stations and in the future seismologist in KOERI will try to increase number of online seismic stations for Marmara Region. After site selection was done the seismologists participated in this project made detailed signal/noise analysis and testing bedrock properties. For this purpose, a portable 3-component seismometer system with gain adjustable up to 10,000 was used for site selection of ISTNET stations. This test has been done for different gains for each site. Final decision of the site selection has been made after making this analysis and then seismometer vault and huts have been installed. Photo 9.4 .1, Photo 9.4 .2, Photo 9.4 .3 and Photo 9.4 .4 show a seismic vault and the basement of the building, two different station huts and installed seismometer, respectively.

Photo 9.4.1 An example of a seismic vault and the basement of the seismic building.(Büyük Sinekli Station-Silivri)



Photo 9.4.2 A typical seismic station hut (Kilyos Station).



Photo 9.4.3 Another type of seismic station building (Büyük Sinekli)



Photo 9.4.4 An example of seismic vault and installed 3-components seismometer in the station hut (Büyük Sinekli).

All the seismic stations of ISTNET contain a voltage regulator, an UPS, a surge protector, a leased-line modem and a data logger (HAKUSAN LS 7000) that is combined with an Analog-Digitizer capability. Photo 9.4 .5, Photo 9.4 .6 and Photo 9.4 .7 show regulator, recording system with UPS and data-logger, surge protector and modem

Photo 9.4.5 A high Voltage regulator used each ISTNET stations.



Photo 9.4.6 An example of installed surge protector (AC and telephone line).



Photo 9.4.7 A leased-line modem, UPS and data logger.


9.5.Operation and Mainenance


This project’s output will be used by the staff of Seismological Observatory of KOERI not only for daily seismological detection purposes but also for producing new scientific results for the entire scientific community in Turkey and in the World. The MARNET and IZINET network data are used to locate earthquakes in Marmara Region for last seven years and the new system will be widely used for routine work in Kandilli because of many advantages of the system. Seismological Observatory of KOERI is working on 24 hours, 365 days basis and has seismologists on duty all the day. This system will be used for locating earthquakes. It will also be used to announce earthquake parameters to media and public. In this section of the KOERI more than 20 seismologists and 3 technicians are working for installation and maintenance of seismic stations in Turkey. This system will reduce the time for detecting earthquake parameters into several seconds to couple of minutes. In the past 10 to 25 minutes were required for locating the earthquakes manually by using paper drum records. The new system has been working completely since August 2002 and some examples of recorded events and automatic locations and epicenter maps are given in Figure 9.5 .16 to Figure 9.5 .20. These figures demonstrate the output of the new system containing seismograms, automatic location results which are displayed as a map. The project team will continually operate and maintain the new system. This new system’s both hardware and software are unique to Turkey and the success of this system will be a model for other institutions and projects. For this reason, project team and other staff of KOERI are giving a higher importance for the system and trying to keep it running smoothly. Due to increasing probability of forthcoming strong earthquake in Marmara region Turkish Telecom (TT) is also giving a higher importance and support to our works in Marmara and Turkey. Seismologists in Kandilli have close contact with technicians and engineers from TT and they are helping to establish new fast line and increase line quality for all seismic stations.

.

Figure 9.5.16 A screenshot from WIN system combining seismic stations from 3 different networks. For instance, KYK belongs to ISTNET, YEL belongs to IZINET and CTT belongs to MARNET networks.



Figure 9.5.17 Same earthquake record as above with some of selected stations displayed in order to arrival times of seismic waves to the stations.



Figure 9.5.18 A screenshot of automatic location results for a recorded earthquake.



Figure 9.5.19 Automatic location results from WIN system for one month period.

Figure 9.5.20 Automatic location results with EQDAQ system for 6 days.



On the other hand, the project team had a contract with a professional telecommunication company to run our fiber optic and telecommunication systems for ISTNET and IZINET networks. This company will continue to support and maintain all available data lines. According to agreement, every day they are inspecting quality of the telephone lines and if the signal is weak they are making necessary corrections. In ISTNET another computer company is agreed to support hardware and software problems if any occurs. The three project members are also living in the Kandilli Campus and if the system has some problems it is sending an alert by mail and telephone and the system can immediately be inspected. Project members have collaboration with Prof. Y. Honkura, Dr. A. Ito and with many other Japanese scientists for at least 3 more years and hope this collaboration will continue with new projects in the future. Both IZINET and a new system will be planned together with our Japanese colleagues and have full support in every aspects of projects. The system can also remotely control acquisition by PC in IZINET or MARNET base station with the help of a remote control software. After installing the fiber optic telecommunication system in the IZINET base station and Iznik center, the system had a continuous internet access for these regions in 2000. Japanese project members can access to the acquisition and analysis software from Japan for technical support and data retrieval purposes at any time.

9.6.Web Page and Internet Connection


As part of this project, project team has attempted to establish the presentation of seismic information in Istanbul and the Marmara Sea region on the Web sites at the Istanbul Municipality office and also at the Kandilli Observatory. The web page is designed in Turkish and English. Basically, the system relies on the automatic hypocenter determination for the WIN format data from integrated observation system. The hypocenter information displayed four figures of seismicity for one day, the past one week, the past one month and the past one year for both regions. More information such as the origin time, location of the epicenter with the depth of certain magnitude events can be obtained by just clicking the epicenter of the event of interest. This information can also be accessed from any internet connection point at any time to monitor recent seismic activity of Istanbul and Marmara Sea region continuously. This web presentation should be very useful for monitoring seismic activity in Istanbul and the Marmara Sea region not only for research purposes but also for disaster prevention efforts of the Istanbul Municipality office. Also, such information can be used for educational purposes to Istanbul citizens including school children, through the enhancement of knowledge on earthquakes. The system completed and announced public and media. The addresses of these web pages are given below for Istanbul and the Marmara Sea region.

For Istanbul:


http://www.koeri.boun.edu.tr/geomap/istanbul/en/index.html

For the Marmara Region:


http://www.koeri.boun.edu.tr/geomap/en/index.html

Figure 9.6 .21 through Figure 9.6 .26 display some seismicity maps and station distribution figures from web pages for Istanbul. Same type figures can be monitored for the Marmara Sea region in above URL. All available seismic stations used in this project are given in Figure 9.6 .27.



Figure 9.6.21 A screenshot of seismicity map for last 24 hours in the vicinity of Istanbul from the new Web page.





Figure 9.6.22 A screenshot of seismicity map for the last 7 days in the vicinity of Istanbul from the new Web page.



Figure 9.6.23 A screenshot of seismicity map for the last one month in the vicinity of Istanbul from the new Web page.



Figure 9.6.24 A screenshot of seismicity map for the last one year in the vicinity of Istanbul





Figure 9.6.25 A screenshot of detailed information about selected one modarate size (M4.5) earthquake occurred nearby Istanbul on Oct. 1, 2002 at 04:21 GMT. Star indicates the mainshock and red circles represent the past one year seismic activity in detail.

Figure 9.6.26 A screenshot of seismic station distribution in the vicinity of Istanbul.



Figure 9.6.27 A screenshot of all available permanent seismic stations used in this project.


9.7.Acknowledgement


The project team would like to acknowledge the support from all the people and companies during site selection, installation and operation of this project. Especially we are thankful to the former director of B.U. Kandilli Observatory and Earthquake Research Institute, Dr. A. Mete Isikara who has always encouraged and supported us. All members also would like to thank the Seismology Laboratory staff for their past and daily support of the 3 networks mentioned above. The following is a list of people and organizations who have given their support:

JICA
PAD A.S.


Turkish Airlines Administration Council
Turk Telekomunikasyon A.S. Directorate of Anadolu District
Turk Telekomunikasyon A.S. Directorate of Istanbul District
Ataturk Airport Customs Directorate
Yaran Bilgisayar Ltd. Sti.
Uzmanlar Tic. A.S.
HAKUSAN Corp.
Prof. Dr. Ken Sudo
Prof. Dr. Omer Alptekin
Prof. Dr. Metin Ilkisik
Yakup Gezdirici
Silivri Municipality
Sile Municipality
Kiyiköy Municipality
TURKCELL

References

Ambraseys N.N., and Finkel, C.F., 1995, The Seismicity of Turkey and Adjacent Areas. Eren Yayincilik, Istanbul, Turkey.

Barka, A. and Relinger, R., 1997. Active tectonics of the Eastern Mediterranean region: deduced from GPS, neotectonics and seismicity data., Ann. Geofis. 40 (3), 587-610.

Baris, S.; Ucer, S. B.; Ito, A.; Kafadar, N.; Alcik, H.; Pinar, A.; Gurbuz, C.; Honkura, Y.; Isikara, A. M., 1996, Local Microearthquake Network in the Western Part of the North Anatolian Fault Zone, Japan Earth and Planetary Sciences Meeting, March, 26 - 29 1996, Osaka, Japan.

Baris, S., Ito, A., Ucer, S.B., Komut, T., Kafadar, N., Ito, A., Pektas, R., Honkura, Y., and Isikara, A. M., 2002, Microearthquake activity in the western extensions of the North Anatolian Fault Zone in the eastern Marmara region, Turkey (1993-1998), Bull. Seism. Soc. Am., 92, pp. 394-405.

Genc, M., and Mazak, M., 2001, Istanbul Depremleri, IGDAS Publication, Istanbul, Turkey.

Ito, A., S. B Ucer, S. Baris , A. Nakamura, Y. Honkura, T. Kono, S. Hori, A. Hasegawa R. Pektas, T. Komut, and A.M. Isikara, 2002, Aftershock activity of 1999 Izmit eaerthquake, Turkey, revealed from microearthquake observations, Bull. Seism. Soc. Am., 92, pp. 418-427.

McKenzie, D.P., 1972, Active Tectonics of Mediterranean region, Geophys. J. R. Ast. Soc., 30, 109-185.

Nakamura, A., Hasegawa, A., Ito, A., Ucer, S.B., Baris, S., Honkura, Y., Kono, T., Hori, S., Pektas, R., Komut, T., Celik, C. and Isikara, A.M., 2002, P-wave velocity structure of the crust and its relationship to the occurrence of the 1999 Izmit, Turkey earthquake and aftershocks, Bull. Seism. Soc. Am., 92, pp. 330-338.

Parsons, T., S. Toda, R. S. Stein, A. Barka, and J. H. Dieterich, 2000, Heightened odds of large earthquakes near Istanbul: An interaction-based probability calculation, Science, Vol. 288, 661-665.

Toksoz, M.N., A. Shakal, and A.J. Michael, 1979, Space-time migration of earthquakes along the North Anatolian Fault Zone and seismic gaps, Pure Appl. Geophys., 117, 1258-1270.

Ucer, S.B., Crampin, S., Evans, R., Miller, A. and Kafadar, N., 1985, The MARNET radio-linked seismometer network spanning the Marmara Sea and the Seismicity of Western Turkey, Geophys. J.R. Ast. Soc., 83, 17-30.

Urabe, T., 1997, WIN system user manual, Hakusan Corporation.

Woith, H., READINESS Project web page, GFZ, Potsdam, Germany.



Establishment of the Integrated Seismic Observation System around Istanbul and the Marmara Region




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