In Kachchh (Gujarat) Earth Quake region, yesterday at 3pm we observed heavy blast sound, what may be the cause

at presently since 2-3 weeks we are observing the small earthe quakes and such sounds what may be the reason for this. The area is Mandvi , Bhuj (small Rann area). Earthe quake is the reason or any other reason may cause this type of Blasting sound and vibration. Yesterday (on 13/03/2008 at 3. 00 pm) we have observed heavy blast type sound. Please note that vibration and motion was very minor but sound was high.