My impression is that GPS shows little or nothing in the way of anomalous deformation before the mainshock - the large foreshocks did not trigger a large slow slip event, for example.

Also, these same people have been claiming an anomaly for EVERY earthquake recently, seemingly, and no good evidence has yet been presented to back up any of those claims.

One can always hope the latest claim is different, and can be backed up, but their track record argues against it.