Crustal tilts around the kalabsha fault, North West of the Nasser lake, as predicted by least-squares collocation of levelling data

Abstract EN

Least-squares prediction using an empirically deduced local covariance function was performed to investigate the horizontal gradient of vertical movements (tilting movements) and possible position of block boundary around the Kalabsha fault, north west of the Nasser Lake, Egypt.

Levelling data covering the Kalabsha area in the interval 1986 - 1992 were used.

First approximated a covariance function of the rates of vertical crustal movement with a Gaussian form function is estimated and used it to segregate signal (rate of vertical movement rate) and noise in observed data.

Then, the signal at grid points of 400 × 400 m2 mesh covering the Kalabsha area was estimated.

After that, the estimated signal was differentiated in space to calculate the tilting movements.

Finally, the position of possible fault zones or blocks boundaries in the Kalabsha area was delineated from the obtained continuous distribution of tilts of the deformed surface.

By the present method, the subsidence in the southern part of the Kalabsha network relative to its northern was well reproduced.

The pattern of tilt movements shows a low zone of tilt movements in the middle of the studied region surrounded by high tilt areas.

The rate of tilt movements reaches about 0.35 microradian/yr in the southern high tilt area.

Moreover, the delineated position of the fault zone or the block boundary in the area is in a good agreement with the wellknown trace of Kalabsha fault.