zonal acceleration from reference PGA

 I have not come across the phrase "zonal acceleration" in relation to the PGA from earthquakes before, what is the context? How is the term being used?
I was curious so I used Chrome and Googled for the terms 'earthquake zonal acceleration' and found this entry in Google Books:
"The zonal acceleration ratio a is the ratio of the peak horizontal ground acceleration to the acceleration due to gravity"
which is on page 112, in the 2nd to last paragraph of:
International Handbook of Earthquake Engineering: Codes, Programs, and Examples. By Mario Paz
In your case the zonal acceleration ratio would be 0.323 and the zonal acceleration would therefore be 0.323 x g = 0.323 x 9.8067 m/sec2 = 3.17 m/sec2
Does that make sense for what you are trying to do?