The circuit uses IC CD4060 which is Binary counter with 10 outputs. Each output goes high one by one in a binary fashion. That means, second output remains high with double time than the first one and so on. The IC oscillates with the capacitor connected to its pin 9 and the resistor (VR1) to its pin 10. The oscillations are fed to the input pin 11 through the 1 Meg resistor. Out of the 10 outputs, only two outputs (Pin 6 and 7) are used to drive two NPN transistors.LED is connected to the collector of T1 through the 100 Ohms current limiting resistor. T1 and T2 are wired as amplifiers. Reset pin 12 of IC is grounded via resistor R1.
So at power on, IC oscillates and first output turns high after few seconds and triggers T1. After few seconds, second output turns on and T2 conducts. The synchronous actions of T1 and T2 give the Strobe light effect from the LED.