Zenith and Azimuth Angle Dependence of Extensive Air Shower Thickness

The arrival time distribution of simulated extensive air shower particles, for 1014􀀀1016 eV showers initiated by protons, for the observation level of the ALBORZ-I array in Tehran, has been investigated. Using the standard deviation of the time dis- tribution as an indicator of the shower thickness, and dening appropriate observation zones on the ground, we found an asymmetry in the shower thickness of slanted show- ers. It seems that the early parts in the shower front are thicker than the late parts. A misinterpretation of the thickness of slanted shower fronts in an other research has been corrected. Implications for improvement of accuracy in the shower axis direction estimation have been discussed.