NATIONAL OBSERVATORY OF ATHENS INSTITUTE OF GEODYNAMICS P.O.BOX 20048, 11810 ATHENS Strong ground motion monitoring in Greece in Greece. D I Dr. Ioannis S. Kalogeras i S K l Research Director
The strong ground motion networks in Greece •There are 3 main Institutions in Greece operating strong motion instruments at a national scale: Institute of Geodynamics, Nat. Observatory of Athens (NOAGI) installations mainly at urban sites Institute of Engineering Seismology & Earthquake Engineering (ITSAK) Institute of Engineering Seismology & Earthquake Engineering (ITSAK) installations mainly at urban sites Public Power Corporation (PPC) installations at dams and thermoelectric plants installations at dams and thermoelectric plants In total, about 200 instruments are in operation in Greece This means a variety of instruments and aims, thus a difficulty in cooperation: Overlaps exist between NOAGI and ITSAK. PPC needs help from NOAGI and ITSAK for maintenance and data processing. However, efforts exist, resulting to common databases, common reports for strong earthquakes, communication for new installations.
The NOAGI strong ground motion network The deployment started back to the 70s, while today consists of 78 installed instruments. Information is available at: Information is available at: http://www.gein.noa.gr/English/new-accelnet-eng/INTRODUCTION.htm The majority of the instruments are installed in urban areas taking into account the The majority of the instruments are installed in urban areas taking into account the seismicity and the urban development, while there are some of them installed at special constructions (dams, Athens metro) and at archaeological sites.
Present situation of NOAGI strong motion network From 70s to nowadays From 70s to nowadays
Local arrays have been implemented with the the support support of of other other organizations organizations (municipalities, public organizations etc).
The records are processed routinely (following the Kinemetrics’ software) and the results are published in printed and electronic formats and the results are published in printed and electronic formats (Stavrakakis et al., 1992; Kalogeras & Stavrakakis, 1995, 1998, 2001, 2007). Strong motion databases have been developed under MsAccess for an easier manipulation of the available data.
Table relationships
Table contents
It is worth to mention the developement of a unified strong motion database (HEAD v1.0) in cooperation with ITSAK and Geophysical Laboratory (Thessaloniki) including records from the networks of the ( ) f f two Institutions processed in a homogeneous manner. In total 677 3-component records from I t t l 677 3 t d f 319 earthquakes are included in HEAD, covering covering the the period period 1973-1999 1973-1999. Relocation of the events, a homogeneous g filtering g technique, q a viewer and a query machine under MsAccess and new more reliable attenuation tt ti relationships l ti hi were th the “products” of this database.
Institute of Geodynamics and SYZEFXIS y SYZEFXIS (meaning “linked together” in Greek) is financed by E.U. and Hellenic State and is implemented by the Society of Information S.A., under the Ministry of Internal Affairs. The budget of the project has been approved till 2013 (www syzefxis gov gr) (www.syzefxis.gov.gr). The hardware (routers, modems, call centers etc.) is given to the Institutions and Organizations for free and there is a Help Desk and a Forum for support on any Organizations for free and there is a Help Desk and a Forum for support on any subject concerning the network. Within the project all the Prefectures, Municipalities, Ministries, Hospitals and Within the project all the Prefectures, Municipalities, Ministries, Hospitals and Health Centers, Police stations, Fire Brigade etc. are linked and take advantage of a wide range of services (data transfer, VOIP, web pages hosting, PKI and SSL, t l teleconferencing, education, etc.). f i d ti t ) Institute of Geodynamics was the first seismological institution that joined the network covering in such a way a new subject in the frame of Syzefxis network, covering in such a way a new subject in the frame of Syzefxis.
Institute of Geodynamics & Syzefxis y y TOWN HALL KASTELLORIZO OTE KASTELLORIZO KASTELLORIZO LAN 2 Mbps/ 512kbbs Router 2 Mbps/ SDSL 4 NATIONAL OBSERVATORY OF ATHENS ATHENS BUILDING WITH SYZEFXIS CONNECTION VPN1, VPN2, …. 2Mbps 2 – 34 LAN Router Mbps SYZEFXIS NET ΣΥΖΕΥΞΙΣ Router LAN PBX 2Mbps PSTN PSTN/ ISDN 1 3 2 REMOTE ADSL
leased lines, radio links, internet connection, combinations etc. Use of different techniques:
Establishment of a system for the telemetric maintenance of the network f th t k The effort aimed to provide the necessary hardware and software in order The effort aimed to provide the necessary hardware and software in order to enhance “traditional” accelerographic instruments equipped with serial interfaces and exhibit various operational characteristics with modern network functionality. This requires not only several upgrades in terms of f f physical interconnections but designing and implementing the necessary intermediate software modules as well. intermediate software modules as well. Since routing and firewalling issues should be solved appropriately, a Central Controller Entity (CCE), hosted in a computer in NOAGI premises, in order to communicate fluently with each remote instrument, one-by-one.
The role of the CCE entity includes several modules The role of the CCE entity includes several modules concerning different purposes: � Software driver modules are used for the CCE entity to directly communicate with each remote serial device via the established IP connection and to download the serial i f information via TCP/IP sockets. ti i TCP/IP k t � A main daemon is responsible to pass any necessary command to the accelerograph of interest or to listen to any activity or response from the remote instrument. Thus the daemon acquires the operating status of the instrument, downloads any new event recorded and stores the information into appropriate log files. � A separate module synchronizes the clocks of all the instruments using an accurate p y g time reference from a GPS-equipped accelerograph, since the instrument maintenance in real-time conditions and the processing of the records are crucial for the network operational reliability operational reliability. � All the gathered information (operational status and records) is available for web access and/or further arithmetic post processing via modules that are implemented separately on a second computer which is hosted in the NOAGI premises separately on a second computer, which is hosted in the NOAGI premises.
Network #1 Accelerograph Interfacing of type A Device Accelerograph Interfacing of type N Device Monitoring … … Computer Logs Accelerograph Interfacing Commands of type A Device Accelerograph Interfacing Web Server of type N Device Network #K
The status report of the instruments
Only the instruments denoted by black triangles are not connected and they are planned to be in the near future .
Deployment of a local dense strong motion array - Athens array Athens array Started in 1996 with 10 instruments. Today includes 27 digital instruments digital instruments. During 1999 Athens seismic sequence gave a database of q g more than 300 records. Recently, two intermediate - depth earthquakes recorded (2006, M=6.9 and 2008, M=6.5) from a distance of 200km.
Athens earthquake (7/9/99, M=5.9), Kythira earthquake (8/1/06, M=6.9), Surface, near-field , Intermediate depth, long distance p , g Pga between 75 and 318 mg, for Pga between 5 and 20 mg, for distances distances between between 20 20 and and distances around 200km distances around 200km. 35km.
1000 1000 100 100 PGA cm/s/s PGA cm/s/s 10 10 P P 1 1 M=5.0 S=2 M=6.0 M 6 0 S 1 S=1 M=7.0 S=0 +/-s +/-s PGA (horizontal components) PGA (horizontal components) 0.1 0.1 1 10 100 1 10 100 R km R km Comparison of recorded pga during Athens 1999 earthquake with Skarlatoudis et al Comparison of recorded pga during Athens 1999 earthquake with Skarlatoudis et al. (2003) relations, according to magnitude and soil conditions. The higher values refer to the closest to the epicenter site (SPLB) which is located at alluvium deposits.
The lower values of pga for 2006 earthquake (M=6.5) compared to Youngs et al. (1997) relations could be attributed to the higher attenuation at the internal part of p the Aegean arc. Again the higher pga recorded at SPLB site.
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