someplace else said 7.
For those not familiar with it, this scale is logarithmic.
A 6.8 is 10 times as much as 6.7
so, a 7 is 1000 times stronger than a 6.7
It is logarithmic, but the whole numbers are the magnitude increase.
Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released, and each increase of 0.2 corresponds to approximately a doubling of the energy released.