So in this scene , we see Shiki dodge an explosion at almost point blank range. It is safe to say that she outsped it given the lack of damage on her; hence, her minimum speed is the speed of the explosion.
So what type of explosive was it? Well, we don't know for sure, but we do know the guy who set it off likes to use pipe bombs . Given that pipe bombs are easy to make and prevent the cops from knowing you bought explosives, we will assume it was a pipe bomb.
Typically, inside of pipe bombs, there is gunpowder rather than a high explosive. This wikipedia article says that this speed is usually 1524 m/s, which is mach 4.44.
Now, what about if it was a common high explosive instead, like C4? Well, this page says that C4 travels at 8750m/s or mach 25.5.
So Shiki's speed is Mach 4.44-Mach 25.5, supersonic+ to high hypersonic