1. Department of Geophysics, Eötvös UniversityPázmány P. s. 1/C, 1117 Budapest, Hungary (frankh@ludens.elte.hu)
2. Netherlands Research Centre for Integrated Solid Earth Sciences, Department of Tectonics and Structural Geology, Vrije Universiteit1081 HV Amsterdam, The Netherlands
3. Vanco Energy CompanyHouston, TX 77046, USA
4. Geodetic and Geophysical Research Institute, Hungarian Academy of SciencesSopron, Hungary