Hmm... I really don't think the blurring is down to the shutter speed.

In ye olden times (also known as 35mm photography), the shutter being open was the only time the film was exposed to the light. The shutter had two 'bits', a top shutter and a bottom shutter. The bottom shutter started fully 'up', covering the film. If you had, say, a 1 second exposure, the bottom shutter would slide down, exposing the film, and 1 second later the top shutter would slide down, covering the film. Then, winding the film on would reset the positions of both shutters.

So, the 'shutter speed' was how long the gap between the top and bottom shutters was open, letting light in to the film.

Now, a fast shutter speed could easily have the two slides moving simultaneously, so that the bottom slide was still covering some of the bottom of the film while the top slide had already started covering the top of the film. Essentially the film was being exposed in 'slices', but it was rarely a problem because it was all happening so very, very quickly.

And, getting to the point, the 'sync speed' of the camera was the fastest shutter speed at which the film was all exposed at once. Above the sync speed, the film was being exposed in 'slices'.

Now, flashes are 'instantaneous' moments of light. They're really, really fast. Really. What happens when you take the picture is the camera opens the shutter, triggers the flash, and closes the shutter. In that tiny, tiny amount of time where the shutter is fully open, the camera gives the electronic signal to the flash to, well, flash, the flash flashes, and then the flash stops flashing.

Since the flash is happening so very, very quickly, you don't get blurring because of a flash. Even very fast things are generally frozen.

With flash photography, the sync speed becomes a misleading indicator of when blurring sets in - a flash photograph at a sync speed of 1/200th will be frozen, while a non-flash photograph at 1/200th could have motion blur.

In general, the only time you get motion blurring on a flash photograph is when you get 'bleeding' from non-flash light. If your subject is lit, you're effectively taking a 1/200th picture 'on top of' the flash-lit picture. That can cause some interesting effects, if it's what you mean to do, by the way.

As I said, that's all 35mm stuff. I don't know how digital shutters work, but I'd be surprised if they were significantly different. (So go on - surprise me?)

Really, though, I think your blurring is down to focusing and depth of field. It does look like there's a 'plane of focus' in your shot, just perhaps not where you want it to be.