Modern band-limited, wide-range and broad-band electromagnetic seismometers with digital registration
Following the new worldwide trends of development of instrumental seismology, the Seismological Observatory in Skopje undertook many activities. It succeeded to be included in the UNDP project Development and installation of telemetred and computerized seismic stations network in SR Macedonia. In connectionwiththis project, LazoPekevski, then a Master ofPhysical Sciencesand an assistantinthe observatory, performed a specialization intheUS Geological Survey – USGS,inGolden, Colorado.
In 1986, the observatory submitted to the Parliament of the Republic of Macedonia a five-year Programme for Development of Seismological Service in SRM. This programmeincluded the Programme for Installation of a Telemetric Network of Seismological Stations in Macedonia. It was planned to equip the existing three seismological stations (Skopje, Valandovo and Ohrid) with new seismometers and digital recorders, and to open new telemetric stations, all connected into a network with computer acquisition and processing of seismological data.
According to an intervention law on retirement, Prof. Dragan Hadžievski, the Head of the observatory, was prematurelyretired on 5 July 1988. From then until 30 September 1989, the acting Head of the observatory is Lazo Pekevski. On 1 October 1989, Ljube Milenkovski, a Doctor of Geographical Sciences and an Associate Professor in the Institute of Geography at the Faculty of Natural Sciences and Mathematics in Skopje, was appointed Head of the observatory. On 9 July 1993, Ljupčo Jordanovski, a Doctor of Civil Engineering and Engineering Seismology, then an Associate Research Professor at the observatory, was appointed Head of the observatory.
Accepting the aforementioned Programme for Installation of a Telemetric Network of Seismological Stations in Macedonia, the Parliament of the Republic of Macedonia allowed funding for the purchase of new seismological and computer equipment. According to a project which was led by Lazo Pekevski, these funds were partly realized in 1991, when sets consisted of three short‑period electromagnetic seismometers type SS‑1 and a digital recorder type SSR‑1 (all products of Kinemetrics Inc., USA) were acquired for the seismological stations in Skopje, Ohrid and Valandovo. The installation in the seat building of the observatory in Skopje was done during March 1991, in the station in Ohrid – on 12 March 1994, and in the station in Valandovo – on 23 March 1994. The exchange of digital seismological data among these stations was realized by a modem, via telephone connections. The centre of data acquisition and analysis was set at the seat building of the Seismological Observatory in Skopje.
Thus, 23 March 1994 is the day of putting into operation of the first telemetric seismological network in the Republic of Macedonia. For some period of time, the later network operated simultaneously with the former network of analog seismological stations.
During the realization of the scientific-research project PLATO, the project partners, the Institute of Earthquake Engineering and Engineering Seismology from Skopje and the National Institute for Geophysics and Vulcanology (INGV) from Italy, cooperated with the Seismological Observatory in Skopje. As a result, a new integrated network of analog and telemetrically connected digital seismological stations was established in Republic of Macedonia. The Seismological Observatory in Skopje obtained additional modern equipment. In 1996, the short-period electromagnetic seismometers type SS-1 RANGER at the stations in Skopje, Ohrid and Valandovo were replaced by wide-range electromagnetic seismometers type WR-1 RANGER (products of Kinemetrics Inc., USA). New telemetric digital stations, each consisted of three short-period electromagnetic seismometers type SS-1 RANGER and one digital recorder SSR‑1, were installed on the Streževo dam (near the town of Bitola), on the Ratevo dam (near the town of Berovo), in the towns of Bitola, Štip, Kriva Palanka and Debar, as well in the village of Gorno Vranovci (near the town of Veles). The data from the network was exchanged with a number of institutions, such as the Strong Motion Laboratory at Institute of Earthquake Engineering and Engineering Seismology in Skopje, the Seismological Network MEDNET of the INGV in Rome and the Euro-Mediterranean Seismological Centre (CSEM) in France. The feedback information on earthquakes that occur in the territory of the Republic of Macedonia enabled much faster and high-quality investigation of the earthquakes.
The modern short-period electromagnetic seismometers type SS‑1 RANGER, set in a way to reflect the ground motions along the vertical direction and the directions North–South and East–West. The seismometersof this type were for the first time purchased by the Seismological Observatory in Skopje from Kinemetrics Inc., USA, in 1991.
Awide-range electromagnetic seismometer type WR‑1 RANGER (production of Kinemetrics Inc., USA). The seismometer contains, in fact, three wide-range electromagnetic seismometers, set in a way to reflect the ground motions along the vertical direction and two perpendicular horizontal directions. The Seismological Observatory in Skopje obtained three WR‑1 RANGER seismometers in 1996.
Due to some problems in the infrastructure, from all above mentioned stations, only the stations in Bitola, Štip and Kriva Palanka, were kept. The first two of these three stations are now permanent station in the telemetric network of Republic of Macedonia, while the station in Kriva Palanka operates as a temporary one.
The seat building of the Seismological Observatory in Skopje after its extension in 1998.
The acquiring of new equipment within the project PLATO released a part of the observatory’s finances approved previously (in 1990) by the Parliament of the Republic of Macedonia for the same purpose. The observatory made new efforts to obtain an additional budget from the Government for extension of the seat building and for upgrading the computer equipment. Thus, during 1998, with a large engagement of the Head of the observatory, Ljupčo Jordanovski, and of all other employees, an extension of the seat building of the observatory in Skopje was done. This provided additional separate offices and a room for every-day analysis of the seismological network data. Ljupčo Jordanovski was the Head of the observatory up to 9 March 2001. On 10 March 2001, this function was again assigned to Lazo Pekevski, then a Doctor of Natural Sciences and an Assistant Professor.
In 2003, a partial renovation of the seismological station in Ohrid was done using a budget obtained from the Government.
The project DIRECTE 2 (Development of Infrastructure for Rapid Earthquake Data Collection and Exchange), 2004–2005, whose leaders were Peter Labak from the Geophysical Institute of the Slovak Academy of Sciences, Bratislava, and Lazo Pekevski from the Seismological Observatory in Skopje, planned to enhance the capacity of the telemetric seismological network in Republic of Macedonia and to implement a real-time exchange of seismological data within this network, as well as with the telemetric seismological stations from abroad.,
Under this project, in 2005, with funding from UNESCO (namely from the programme Slovac Aid), the digital recorders type SSR-1 in the stations in Skopje, Ohrid, Valandovo, Bitola and Štip were replaced with digital recorders type Wave24. (Wave24, a product of the company MicroStep-MIS from Slovakia, is a seismological measuring system, which uses a 24-bit digitizer and has an appropriate data acquisition.) These stations were interlinked via Internet in a new telemetric network. Again via Internet, this network was linked with a number of seismological stations from the Balkans, which enabled a real-time exchange of seismological data. The central acquisition and processing of seismological data for the Republic of Macedonia was prescribed to seat building of the Seismological Observatory in Skopje, where new computer equipment was set and appropriate softwares in the operating system LINUX were installed. The software Seismic Handler was installed for data processing. Through the web-site of the observatory, the records of the seismological stations in Republic of Macedonia used to be available to the seismological institutions from around the world and to the public.
Modern equipment of the seismological station at seatbuilding of the Seismological Observatory in Skopje. (Up and left) electromagnetic seismometers SS‑1 (short-period) and WR‑1 (wide-range period); (up and right) the SSR‑1 digital recorder; (down and left) the Quanterra–Q330 digital recorder; (down and right) the Wave24 digital recorder and the obtained record on a computer monitor.
All new equipment is officially put into operation on 3 February 2006. On 29 July 2006, in the town of Kruševo, at a temporary location, a digital seismological station, consisted of three SS‑1 seismometers and one Wave24 digital recorder, was installed. The station was also included in the above described exchange of seismic data in real time. In 2009, the Wave24 digital recorder at the station in Skopje was replaced with a Quantera-Q330 digital recorder (a product of Kinemetrics Inc., USA).
The described new increasing of the capacity of the telemetric seismological network in Republic of Macedonia provides detailed information on seismicity of the territory of the Republic and the surrounding areas. This has a direct impact on the precision in determining the seismic hazard, and, consequently, on the input data for relevant codes of construction of buildings. The internal and external real-time data exchange of the seismological network in the country allows obtaining fast and reliable data about the earthquakes. Thus, the readiness of the Republic of Macedonia for a case of strong earthquake is particularly increased, since the fast information about a strong earthquake enables also fast actions and measures for protection of the population.
The seismological station at the seatbuilding of the Seismological Observatory in Skopje: real-time digital data from the seismological stations in the Republic of Macedonia and the Balkans (left) and their analysis with the software Seismic Handler (right).
Lazo Pekevski performs the function Head of the observatory until 14 October 2007. On 15 September 2007, Ljupčo Jordanovski, then a Research Professor, was again appointed Head of the observatory. On 15 September 2009, Lazo Pekevski, then an Associate Professor, was again appointed Head of the observatory. Ljupčo Jordanovski died on 7 October 2010. Lazo Pekevski finished his Head’s mandate on 14 September 2011, when his University title was Research Professor. On 15 September 2011, Vera Čejkovska, a Doctor of Physical Sciences and, then an Assistant Professor,was appointed Head of the observatory (her present university title is Associate Research Professor).
The Ministry of Education and Science of the Republic of Macedonia, after the visit of the Minister Nikola Todorov to the observatory on 15 March 2011, provided funds for new equipment of the observatory. Thus, during 2011, five personal computers were received, and, at the end of the same year, two modern digital seismic stations, each consisting of a package EpiSensor-Model FBA ES-T and a digital recorder type Quantera-Q330HRS (products of Kinemetrics Inc, USA) were purchased. Each package EpiSensor–Model FBA ES-T consists of three broadband seismic sensors / accelerometers EpiSensor, which reflect the ground motions movement along the vertical direction and two horizontal directions.
The observatory plans to install the new seismic stations at locations in the town of Debar and in the Delčevo-Berovo area. Unfortunately, due to very unfavorable financial situation of the observatory, driven by the continued reduction of the budget for the seismological service, these installations can not be realized soon.
According to an application project for monitoring of the regular and induced seismicity in the area around the accumulation for the Kozjak dam (the municipality of Makedonski Brod) in the period 2004–2008, the observatory maintained in 2003–2008three digital seismic stations, owned by the Macedonian Power Plants Inc. The locations of the stations were at the Kozjak dam and in the villages of Samokov and Belica. The monitoring at these stations continued, in fact, also during the period 2009–2011, at it was reported to the Macedonian Power Plants Inc.
According to a new application project for monitoring of the regular and induced seismicity in the areas around the accumulations for the Kozjakdam (the municipality of Makedonski Brod) and St. Petka dam (near the town of Skopje) in the period 2012-2014, the observatory has been maintainingthree digital seismic stations, two of which (at the Kozjak and St. Petka dams) are owned by Macedonian Power Plants Inc., and one is owned by the observatory itself.
One of the two packages EpiSensor−Model FBA ES-T provided for the Seismological Observatory in Skopje by the Ministry of Education and Science of the Republic of Macedonia in 2011.
The two digital recorders Quantera–Q330HRS provided for the Seismological Observatory in Skopje by the Ministry of Education and Science of the Republic of Macedoniain 2011.
In 2010, within an application project for seismic monitoring of the area around the accumulation for the Lisiče dam (near the town of Veles), the observatory maintained its own seismological station at the dam.
According to an application project for monitoring of the regular and induced seismicity in the area around the accumulation for the Kneževo dam (hydrosystem “Zletovica”, near the town of Probištip) from October 2012 to October 2013, the observatory has been maintaining its own digital seismic station at the Kneževo dam.