Mortgage applications fell slightly this past week after experiencing a dramatic 15% rise just seven days earlier, the Mortgage Bankers Association said Wednesday. The market composite index — a measure of loan volume — decreased 0.7% on a seasonally adjusted basis  for the week ending March 11. On an unadjusted basis, the index fell 0.5% when compared to the previous week. The four-week moving average for the seasonally adjusted market index is up 4.9%, while the four-week moving averages for the purchase index and refinance index are up 1.6% and 6.6%, respectively. Refinancing activity during the period increased to 66.4% of total applications, compared to 65.5% a week earlier. Meanwhile, the average interest rate for a 30-year, fixed mortgage dropped to 4.79% from 4.93% a week earlier. In addition, the average rate for a 15-year, fixed-rate mortgage declined to 4.03% from 4.17%. Write to Kerri Panchuk.