Hello,
As MK posted: "As long as your equation is correct and complied with project regulation, then it's ok."
So, with your project regulation, in this case UBC code, if you read it you will find the formulas to calculate the seismic factor.
Use the values defined for your specific project (ZONE, Na, etc.) with those formulas and you will achieve the value you must consider for your seismic acceleration. Maybe 0,4 G's maybe not. Just a code checking will give you the answer.
IMPORTANT: Read all the code for any clarifying notes.
Regards,
PG