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| Titel |
The contribution of engineering surveys by means of GPS to the determination of crustal movements in Istanbul |
| VerfasserIn |
M. Özyaşar, M. T. Özlüdemir |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 11, no. 6 ; Nr. 11, no. 6 (2011-06-17), S.1705-1713 |
| Datensatznummer |
250009490
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| Publikation (Nr.) |
 copernicus.org/nhess-11-1705-2011.pdf |
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| Zusammenfassung |
| Global Navigation Satellite Systems (GNSS) are space based positioning
techniques and widely used in geodetic applications. Geodetic networking
accomplished by engineering surveys constitutes one of these tasks. Geodetic
networks are used as the base of all kinds of geodetic implementations, Co from
the cadastral plans to the relevant surveying processes during the
realization of engineering applications. Geodetic networks consist of
control points positioned in a defined reference frame. In fact, such
positional information could be useful for other studies as well. One of
such fields is geodynamic studies that use the changes of positions of
control stations within a network in a certain time period to understand the
characteristics of tectonic movements. In Turkey, which is located in
tectonically active zones and struck by major earthquakes quite frequently,
the positional information obtained in engineering surveys could be very
useful for earthquake related studies. For this purpose, a GPS (Global
Positioning System) network of 650 stations distributed over Istanbul
(Istanbul GPS Triangulation Network; abbreviated IGNA) covering the
northern part of the North Anatolian Fault Zone (NAFZ) was established
in 1997 and measured in 1999. From 1998 to 2004, the IGNA network was
extended to 1888 stations covering an area of about 6000 km2, the whole
administration area of Istanbul. All 1888 stations within the IGNA network
were remeasured in 2005. In these two campaigns there existed 452 common
points, and between these two campaigns two major earthquakes took place, on
17 August and 12 November 1999 with a Richter
scale magnitude of 7.4 and 7.2, respectively. Several studies conducted for estimating the horizontal
and vertical displacements as a result of these earthquakes on NAFZ are
discussed in this paper. In geodynamic projects carried out before the
earthquakes in 1999, an annual average velocity of 2–2.5 cm for the stations
along the NAFZ were estimated. Studies carried out using GPS observations in
the same area after these earthquakes indicated that point displacements
vary depending on their distance to the epicentres of the earthquakes. But
the directions of point displacements are similar. The results obtained
through the analysis of the IGNA network also show that there is a common
trend in the directions of point displacements in the study area. In this
paper, the past studies about the tectonics of Marmara region are summarised
and the results of the displacement analysis on the IGNA network are discussed. |
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