Investigating the Effects of Earthquakes Using HEPOS.

KTIMATOLOGIO S.A. developed the HEllenic POsitioning System (HEPOS) for facilitating the establishment of the National Cadastre in Greece. HEPOS is a modern RTK-network consisting of 98 permanent GPS reference stations distributed throughout Greece. Like in any other RTK-network, the coordinates of the reference stations must be estimated with high accuracy, on the order of 1 cm. This requirement is a great challenge for HEPOS, due to the strong geodynamic effects taking place in Greece. Besides the slow displacements caused by the individual velocities of the different tectonic plates, abrupt displacements may occur as a result of strong earthquakes. During the first months of the operation of HEPOS, several strong earthquakes (ML >6.0) with different characteristics took place in certain areas of Greece. By post-processing and analyzing GPS observations of the reference stations of HEPOS, it was proved that some earthquakes have detectable effects on the positions of the reference stations. The paper describes the methodology that has been used for revealing these effects as well as the results that have been obtained. [ABSTRACT FROM AUTHOR]