Write the value of the underlined digit 5.349

Answer is in the attachment below.

So we want to know what is the difference in magnitude of a large quake M(l) and a small quake M(s) in the Richter scale if the amplitude of a large quake A(l) is 1000 times bigger than the amplitude of a small quake A(s) and the formula is M(l)-M(s)=log{A(l)/A(s)}. So the large amplitude is 1000 bigger than the small amplitude: A(l)=1000*A(s). When we insert that into the formula we get:

M(l)-M(s)=log{1000*A(s) / A(s)}, because the A(s) cancel out, so we get: 
M(l)-M(s) = log{1000} = 3. 

So the difference in magnitude on the Richter scale is M(l)-M(s)=3.