What is the difference between Mach cone and shock wave in aerodynamics?

[TimeRip496]

Is mach cone the area of the shock wave or the wave front of the Mach wave?
Usually the diagram for mach cone is this,

However I still see some author states that the Mach cone is the shock wave. Shouldn't the shock wave be at the intersection(between the circles) and if the Mach cone is about the shock wave, shouldn't the diagram be like this instead?

 

[A.T.]

However I still see some author states that the Mach cone is the shock wave. Shouldn't the shock wave be at the intersection(between the circles)

Imagine there are not just 3, but many more circles (the sound is generated continuously). Where would their intersection lie?

 

[lekh2003]

Try drawing a thousand circles in your cone. Where is the intersection now? Unless of course, sound is only generated a three intervals.

 

[CWatters]

Take a look at the bow wave on a boat. It extends out in a v shape just like the shock wave of an aircraft. The resulting wave eventually reaches the bank where it appears to move along the water's edge in much the same way that a shock wave passes over the ground.

The circles on the drawings of a shock wave don't really exist because the process is continuous.