Kinematics engine of the ongoing deformation field around Cairo, Egypt

• Autorzy: Badavy A. , Issavy E. , Hassan G. , Tealeb A.
• Języki publikacji: EN

Abstrakty

EN

Kinematics engine of the ongoing deformation field around Cairo, Egypt, has been investigated from earthquakes, repeated GPS and gravity observations. First results provided from this combined strategy are presented, by focusing on both stress field and surface kinematics. The spatio-temporal distribution of earthquakes reveals that the Cairo region has suffered not only from interplate earthquakes but also from inland seismic dislocations. Earthquake focal mechanisms indicate that the stress field around Cairo is dominated by the transtensional stress regime (normal faulting with strike-slip component). The results of deformation analysis indicate three different deformation zones in the investigated area. The northem part dominates as a compressional area with a magnitude of 0.19 microstrain/year. The compressions in this area are generally in NW-SE direction. Hwever, an extensional area a magnitude of 0.21 microstrain/year in the NE-SW direction has been observed in the southern part. The central part of the investigation area seems to be in a state of no significant deformation. Repeated gravity measurements around Cairo proved an existence of considerable temporal variations of gravity. These non-tidal changes could be explained by dynamics processes within the upper crust related to the development of local stress conditions. The comparison between the observed GPS and gravity shows a remarkable agreement and provides a convincing explanation for the observed fluctuations with seismic activity.

Słowa kluczowe

EN

earthquakes; Global Position System; gravity; deformation; Egypt

• Wydawca: Instytut Geofizyki PAN
• Czasopismo: Acta Geophysica Polonica
• Rocznik: 2003
• Tom: Vol. 51, nr 4
• Strony: 447--458
• Opis fizyczny: Bibliogr. 26 poz.

Twórcy

autor

Badavy A.

• National Research Institute of Astronomy and Geophysics 11421-Helwan, Cairo, Egypt

autor

Issavy E.

• National Research Institute of Astronomy and Geophysics 11421-Helwan, Cairo, Egypt

autor

Hassan G.

• National Research Institute of Astronomy and Geophysics 11421-Helwan, Cairo, Egypt

autor

Tealeb A.

• National Research Institute of Astronomy and Geophysics 11421-Helwan, Cairo, Egypt

Bibliografia

• 1. Altiner, Y., 1999, Analytical surface deformation theory for detection of the Earth's crust movements, Springer-Verlag, Berlin.
• 2. Badawy, A., 1996, Seismicity and kinematic evolution of the Sinai plate (Ph.D. thesis), L. Eotvos University Budapest, 115 p.
• 3. Badawy, A., 1998, Earthquake hazard analysis in northern Egypt, Acta Geod. Geoph. Hung. 33, 2-4, 341-357.
• 4. Badawy, A., 2001a, Status of the crustal stress as inferred from earthquake focal mechanisms and borehole breakouts in Egypt, Tectonophysics 343, 49-66.
• 5. Badawy, A., 2001b, The present-day stress field in Egypt, Ann. di Geofis. 44, 3, 495-509.
• 6. Badawy, A., and A.K. Abdel-Fattah, 2001, Source parameters and fault plane determinations of the 28th December 1999 northeastern Cairo earthquakes, Tectonophysics 343, 1-2, 63-77.
• 7. Badawy, A., and F. Horvath, 1999a, Seismicity of the Sinai sub plate region: kinematic implications, J. Geodyn. 27, 451-468.
• 8. Badawy, A., and F. Horvath, 1999b, Sinai sub plate and kinematic evolution of the northern Red Sea, J. Geodyn. 27, 433-450.
• 9. Badawy, A., and F. Horvath, 1999c, Recent stress field of the Sinai sub plate region, Tectonophysics 304, 385-403.
• 10. Beutler, G., M. Rothacher, T. Springer, J. Kouba and R.E. Neilan, 1999, The international GPS Service (IGS): An interdisciplinary service in support of Earth sciences. In: "IGS Directory 1999", Intern. GPS Service, Pasadena.
• 11. DeBoor, C., 1978, A Practical Guide to Splines, Springer-Verlag, Berlin.
• 12. DeMets, C., R. Gordon, D.F. Argus and S. Stein, 1990, Current plate motions, Geophys. J. Int. 101, 425-478.
• 13. Forsyth, D.W., and S. Uyeda, 1976, On the relative importance of the driving forces of plate motions, Geophys. J. R. Astron. Soc. 43, 163-200.
• 14. Groten, E., and M. Becker, 1995, Methods and experience of high precision gravimetry as a tool for crustal movement detection, J. Geodyn. 19, 141- 157.
• 15. Kebeasy, R., 1990, Seismicity. In: R. Said (ed.), "Geology of Egypt", Balkema, Rotterdam, 51-59.
• 16. Longman, I.M., 1959, Formulas for computing the tidal accelerations due to the moon and the sun, J. Geophys. Res. 64, 2351-2355.
• 17. Mobil Oil Cooperation, 2001, Geology of Egypt, A Technical Reprint, 156 pp.
• 18. Mrlina, J., 1997, Temporal variations of gravity in western Bohemia: period 1993-1996, Studia Geoph. et Geod. 41, 307-318.
• 19. Mrlina, J., 2001, Repeated measurements of gravity as a contribution to geodynamic investigations: two examples from Europe, Bull. NRIAG, 331-341.
• 20. Niebauer, T.M., and J.E. Faller, 1991, Absolute gravimetry: Environmental noise limits. In: C. Poitevin (ed.), "Non Tidal Gravity Changes, September 5-7, 1990, Luxembourgh", Cahiers du Centre Europeen de Geodynamique et de Sejsmologie 3, 39-45.
• 21. Richardson, R.M., S.C. Solomon and N.H. Sleep, 1979, Tectonic stress in the plates, Rev. Geophys. Space Phys. 17, 981-1019.
• 22. Richter, B., 1995, Cryogenic gravimeters: Status report on calibration, data acquisition and environmental effects. In: C. Poitevin (ed.), "Non Tidal Gravity Changes, September 6-8, 1994, Luxembourgh", Cahiers du Centre Europeen de Geodynamique et de Seismologie 11, 125-146.
• 23. Rothacher, M., G. Beutler, W. Gurtner, E. Borck-Mann and L. Mervart, 1996, BERNESE GPS Software (Version 4.0), Rothacher and Mervart (eds.), Astron. Inst., University of Bern, Switzerland, 417 pp.
• 24. Said, R., 1962, The Geology of Egypt, Elsevier, Amsterdam.
• 25. Shukri, N., 1953, The geology of the desert east of Cairo, Bull. Inst. Desert, Egypt 3, 89-105.
• 26. Zoback, M.L., 1992, First and second order pattern of stress in the lithosphere: The world stress map project, J. Geophys. Res. 97, 11703-11728.