Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Kamal Sakr ¹

Affiliations
1 National Research Institute of Astronomy and Geophysics, Helwan, Cairo, EG

Abstract

On 12^th October 1992 the Cairo city in Egypt was hit by an earthquake with a magnitude of mb=5.8. This earthquake occurred at Dahshour area, 35 km southwest of Cairo. Monitoring of recent crustal movement by the Global Positioning System (GPS) is carried out during the period 1999-2003 in the epicentre area. The tectonics as well as seismotectonics of Dahshour area is investigated. Three seismogenic faults that trend E-W, NW-SE and NE-SW affect the area. A11 these faults are nonnal faults; tensional stresses are predominant. The results obtained from the GPS measurements show significant horizontal movements during the period of observation about 8mm/year. The observed horizontal movements are comparable with the tensional stress obtained by fault plane solutions of earthquakes. The extensional and compressional strains are estimated to be +0.4 and -0.2 microstrain/y.

Keywords

Geodetic data, Focal mechanism, Normal faults, Cairo, Egypt.

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Supriya Likhar ¹, Madhav N. Kulkarni ¹, Kamal Sakr ²

Affiliations
1 Indian Institute of Technology, Bombay - 400 076, IN
2 National Research Institute of Astronomy and Geophysics, Halwan, Cairo, EG

Abstract

After the occurrence of the 26^thJanuary 2001 Bhuj earthquake, of magnitude 76, the Global Positioning System (GPS) team of the Indian institute of Technology Bombay (IITB) set up an extensive GPS network in the Bhuj region of Gujarat. For studying the crustal deformations in this region, geodetic data was collected for three epochs, VIZ February 2001, February 2002 and February 2003, using dual frequency GPS receivers.

From the GPS data processing results using the Bernese software, the displacement velocities of the geodetic points and the strain parameters in the Bhuj region of Gujarat were derived. The maximum displacement value observed is 78 mm/year during the period 2001-2002, immediately after the occurrence of the earthquake, at the GPS station CHIT, on die east of the epicentei. This displacement value decreased and reached 9 mm/year during the period from 2002 to 2003, which indicates that the area became stable again within two years of the earthquake occurrence Compressional stram is more dominant close to the epicenter of this earthquake and an extensional strain is observed far SW to the epicenter.

Keywords

Crustal Deformation, Bhuj Earthquake, GPS Measurements, Strain, Gujarat.

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