Geomagnetic Measurements in Macedonia

Transcription

1 Geomagnetic Measurements in Macedonia T. Delipetrov 1*, J. Rasson 2, M. Delipetrev 1 1 Faculty of Mining and Geology, Goce Delcev Stip, R. Macedonia 2 Institut Royal Meteorologique, Centre de Physique du Globe, B-5670 Dourbes Viroinval, Belgique todor@rgf.ukim.edu.mk (Todor Delipetrov) Abstract From 2002 to 2003 the scientific team in the Department of Geology and the Geophysics at the Faculty of Mining and Geology Stip led by Dr. Jean Rasson (from the Royal Meteorological Institute - Geomagnetic Observatory in Dourbes, Belgium) developed the basic geomagnetic net of 18 measure points on the territory of the Republic of Macedonia. During 2003 surveys were carried out on all measure points of the magnetic field (T, D, I). It was the first defining of the basic parameters of normal geomagnetic field in the territory of the Republic of Macedonia. Measurements were carried out with the equipment from the Observatory in Dourbes, Belgium. The Law for Seismological Investigations with Geomagnetic Investigations which is currently in the process of amendments opens the possibility for establishing a Geomagnetic Observatory in the territory of the Republic of Macedonia. So far, detailed measurements have been carried out on several localities in order to meet the requirements of INTERMAGNET for the determination of the site for the founding of the Observatory. It was determined the construction site to be in Mt. Plackovica. Actions have also been taken with the government to obtain the site. Due to the mentioned above our presence in Kakioka will be of great. 1. Introduction Over the past years the geomagnetic measurements carried out on the territory of the Republic of Macedonia and on other territories of former Yugoslavia were conducted by the Grocka Geomagnetic Observatory in Belgrade. After the declaration of independence of the Republic of Macedonia, activities started for establishing a geomagnetic observatory in the country. In that regard, the project entitled Establishing a Geomagnetic Observatory on the Territory of the Republic of Macedonia According to the INTERMAGNET Standards started implementation as a joint project between the Faculty of Mining and Geology - Department of Geology and Geophysics and the Royal Meteorological Institute - the Observatory in Dourbes. Project leaders are Prof. Dr. Todor Delipetrov and Dr. Jean Rasson. The paper presents the results obtained during the past three years. The activities extended by Dr. Jean Rasson in the geomagnetic investigations and the creation of the net for the repeat stations and the selection of the site for the geomagnetic observatory, particularly the transfer of knowledge and training of educated people in the field of geomagnetism are worth of note. 2. General The Republic of Macedonia occupies an area of km 2 in the central part of the Balkan Peninsula. The geomagnetic observatories in neighboring countries are as follows: - Panaguriste, Bulgaria; - Pedeli, Greece; - Grocka, Serbia and Montenegro; - Aquila, Italy. 105

2 Figure 1. Geomagnetic observatories in neighboring countries The territory of the Republic of Macedonia covers a small area. Its evolution, however, is rich in geological event, in various kinds of rocks, a large number of rare minerals, volcanism, seismicity and pronounced tectonics. These characteristics make the area interesting for geological and geophysical studies. According to the global tectonic regional setting of the Balkans, the territory of the Republic of Macedonia includes part of the Rhodop mass to the east, and the Dinaride - Alpine system to the west. The territory has been divided into tectonic regional settings based on investigations carried out so far: Figure 2. Map of the regional tectonic setting - I. Cukali - Krasta; II. Western Macedonian zone; III. Pelagonian massif; IV. Vardar zone; V. Serbo - Macedonian massif; VI. Kraistide zone 106

3 3. Investigations carried out on the geomagnetic field Geomagnetic investigations can be divided into three periods: the period that commenced in the XIX century and terminated in 1945, the second period is that from 1945 to 1991 when the country was part of former Yugoslavia and the last period from the declaration of independence in 1991 to the present time. During the first period owing to the unstable political circumstances and scientific - technological backwardness of the Turkish Empire and then the Kingdom of the Serbs, Croats and Slovenians, only scientists from European countries (in rare occasions and in special expeditions) carried out investigations on the magnetic field of the Balkan area and on a small part of the territory of Macedonia. These investigations are of historic importance, but due to their incidental implementation and the rare net of observations they do not allow any deep scientific understanding of the geomagnetic field. During the period of Former Yugoslavia, a geomagnetic observatory was established in Grocka near Belgrade. It initiated and carried out geomagnetic investigations such as permanent observations of the geomagnetic field and occasional measurements all over Yugoslavia. It conducted field investigations such as defining the areas with geomagnetic anomalies. The net of geomagnetic stations included two on the territory of Macedonia, those in Ohrid and Strumica. During the 1960s the territory of Yugoslavia was investigated with relatively dense terrestrial geomagnetic point net. A map of vertical Z component of the anomalous geomagnetic field for Yugoslavia the scale 1 : was compiled. Figure 3. Map of vertical Z component of the geomagnetic field of Macedonia During the period after the independence, the Department of Geology and Geophysics purchased proton magnetometers to be used during the investigations of the geomagnetic field anomalies in respect to ore deposits. The instruments have also been used in measurements carried out on the territory in respect to archeomagnetism and structural composition of certain terrains. During the implementation of the project Establishing a Geomagnetic Observatory in the Republic of Macedonia According to INTERMAGNET Standards, a team of researchers from the Faculty received additional training in the Royal Meteorological Institute - the Observatory in Dourbes, Belgium in the period This cooperation continued during the implementation of the Tempus Project Geomagnetic Measurements and Quality Standards. According to the activities, five candidates for trainers and two professors from the Faculty in Stip attended lectures on investigations, measurements and practical exercises held by Dr. Jean Rasson from the Observatory in Dourbes. The attendance and presentation extended by the professor from ZAMG, Vienna was invaluable. 107

4 The instruments purchased and used during the Tempus Project Geomagnetic Measurements and Quality Standards includes: - Theodolite Zeiss 010 A and Theodolite Lemi 203, - Variometer Lemi 008. We are grateful to the Royal Meteorological Institute - the Observatory in Dourbes, Belgium for the construction of variometer LAMAMAK. Figure 4. From the training in Dourbes 4. Measurements in Macedonia The first geomagnetic measurements carried out in Macedonia were those in Ohrid on 20 October 2002 on Mt Galicica on a spot with coordinates as follows: Lat: 40 57'23"N Long: 20 48'51"E Alt: 1691m. The spot is more than 100 meters far from the main road that connects Ohrid and Resen. The equipment used included: 1. 1 Diflux/GPS receiver type FLM3/A serial Proton magnetometer Geometrics G816 ( electronics + sensor ) serial Geodetic Tripod 4. 1 Monocular digital compass KVH Data scope II pn# Serial Portable Dell computer The equipment measured the declination, inclination and total field. Such measurements of the geomagnetic field necessitate finding the targets first. The target should be such that will not disappear in the near future e. g. churches, big antennas, mosques etc. The next step includes finding the azimuth and description of the targets that will help future measurements on the same spot and avoid finding targets again. Normally, the researchers selected several targets. From the computer we read all data recorded by the variometer and proton magnetometer important for the declination, inclination and total field. All data collected were entered into the computer. However, in our case we did not use a variometer and proton magnetometer for the measurements in Ohrid. Instead, we used the data from the closest magnetic observatories such as the magnetic observatory of Pedeli in Greece, Aquila in Italy, Grocka in Serbia and Montenegro etc. The results obtained made it possible to carry out complete magnetic measurements. During 2003 a total net of repeat stations for Macedonia was compiled. 108

5 Figure 5. Map of geomagnetic stations 1. "Bajlovce" 2. "Crna Skala" 3. "Gradot Island" 4. "Egri" 5. "Galicica" 6. "Luke" 7. "Mavrovo" 8. "Nikolic" 9. "Plackovica" - location for geomagnetic observatory 10. "Ponikva" 11. "Prilep lake" 12. "Sv. Marija Precesna" 13. "Slivnica" 14. "Tetovo-Zelino" 15. "Vodno" Table 1. Geographic coordinates of the measured stations Measure point Geographic latitude Geographic longitude Altitude 42 o 13' 16" 21 o 55' 17" 592 m 41 o 59' 41" 22 o 47' 28" 833 m 41 o 23' 15" 21 o 57' 06" 317 m 40 o 57' 56" 21 o 26' 54" 626 m 40 o 57' 23" 20 o 48' 51" 1684 m 42 o 20' 39" 22 o 16' 29" 1180 m 41 o 42' 58" 20 o 43' 38" 1418 m 41 o 15' 54" 22 o 44' 36" 300 m 41 o 47' 41" 22 o 18' 13" 677 m 42 o 01' 35" 41 o 24' 11" 41 o 37' 38" 41 o 36' 54" 41 o 59' 09" 41 o 58' 40" 22 o 21' 29" 21 o 36' 32" 21 o 11' 36" 22 o 51' 46" 21 o 04' 46" 21 o 24' 57" 1618 m 870 m 837 m 1252 m 522 m 569 m The measurements made it possible to compile maps for the total vector T, declination D and inclination I. 109

6 Figure 6. Map of total vector, T Figure 7. Map of declination, D Figure 8. Map of inclination, I 5. Conclusion The activities carried out so far resulted in: - Final decision that Mt. Plackovica, Eastern Macedonia to be the site for the geomagnetic observatory; geomagnetic gradient at this place is 1 nt/m. - Creation of a network of repeat stations; - Compilation of maps of the total vector T, declination D and inclination I. The activities carried out are a good ground for establishing the geomagnetic observatory so that Macedonia can join the countries that give their contribution to the following and the study of the geomagnetic field. References [1] Tectonics of Macedonia - Milan Arsovski [2] Map of Z - component of geomagnetic field in Republic of Macedonia [3] Establishing a geomagnetic observatory in the Republic of Macedonia according to the standards of INTERMAGNET - Final report 110