Mortgage rates skyrocketed for the third time in the past four weeks and are now at their highest levels since last fall.

The average 30-year fixed rate shot up by 41 basis points from the previous week, to 6.37 percent. A basis point is one-hundredth of a percentage point. This week’s 30-year fixed is at its highest level since Oct. 17, when it was 6.49 percent.

Meanwhile, the average 15-year fixed — a popular option for refinancing — also rose 41 basis points, to 5.87 percent. The average jumbo 30-year fixed rose 39 basis points, to 7.55 percent.

Adjustable-rate mortgages also moved up this week. The one-year adjustable-rate mortgage rose 10 basis points, to 5.56 percent. The popular 5/1 ARM rose 27 basis point, to 5.77 percent.

Mortgage rates have risen substantially for three out of the four weeks since Jan. 23, when the 30-year fixed bottomed out at 5.57 percent. That week, mortgage rates hit their lowest levels since March 2004.

The recent surge in mortgage rates offers more evidence that Federal Reserve interest rate cuts do not directly determine short-term mortgage rate performance. The Fed cut the federal funds rate by 75 basis points on Jan. 22 in an emergency move designed to spark the slowing U.S. economy. The Fed then slashed rates an additional 50 basis points at its regularly scheduled meeting on Jan. 30.

Some observers voiced hopes that the dramatic action would force mortgage rates lower and bring new life to the sagging U.S. housing market. However, since the Jan. 22 cut, mortgage rates have actually risen by 80 basis points. Rates have climbed by at least 18 basis points in three out of the past four weeks.

A drop in requests for mortgage loans this week also appeared to confirm that higher mortgage rates are dampening homeowner enthusiasm for refinancing. Mortgage loan application activity fell for the second consecutive week. Application volume for the week ending Feb. 15 dropped a seasonally adjusted 22.6 percent from the previous week’s reading, according to statistics from the Mortgage Bankers Association.

Refinancing activity took a particularly hard hit, dipping a seasonally adjusted 27.9 percent from the previous week.

Until the last two weeks, mortgage application activity had risen each week since the beginning of the year.