The distance the plates moved each year X the motion that could be released = the number of years before the next earthquake

The distance the plates moved each year X the size of the gap between the side of one plate and the other plate = the number of years before the next earthquake

The size of the gap between the side of one plate and the other plate X the distance the plates moved each year = the motion that could be released

The distance the plates moved each year X the number of years since the last big earthquake = the motion that could be released