WARRENTON, VA., SEPT. 2 -- Beth Moorman, 14, a freshman at Georgetown Day School in Washington, D.C., took the blue ribbon in the Virginia Horse Show Association's hunt seat medal final today as the 91st annual Warrenton Horse Show closed.

Shannon Nutt, 13, of Middleburg, Va., won the pony equitation final.

Moorman, whose goal is to win the National Horse Show, is for now content to set her sights on the Maryland Horse Show Association finals to be held in two weeks.

Overwhelmed with her accomplishment, she said: "I've only been competing on the A circuit for a year, I can't believe I actually won."

Both the pony and the hunt seat competitions are judged solely on the rider's performance. Riding Fritz And Bill, a horse she has been training on for the past year, Moorman defeated a field of 12 by acrobatically navigating no fewer than eight 3 1/2-foot fences, skillfully performing a series of walk, trot and canter exercises and successfully performing a complicated combination of equitation maneuvers assigned by the judging panel.

According to VHSA rules, the judges can choose any of 18 different tests for the riders to perform; from mounting and dismounting their horse to jumping a sequence of fences to trading horses with the other riders in the ring. Riders must demonstrate a keen ability to control and guide their mount.

The pony and the hunt seat finals are a culmination of the 1990 VHSA show circuit. Riders participating in today's events need to qualify with a combination of points and ribbons to be eligible for the finals. RESULTS

Pony Equitation Final: 1st -- Shannon Nutt, 13, Middleburg, Va.; 2nd -- Shawna Stout, 15, Rockville; 3rd -- Holly Sorensen, 13, Fairfax; 4th -- Margaret Stewart, 12, Washington; 5th -- Kelly Thomel, 15, Virginia Beach; 6th -- Karyn Zambrano, 17, Clifton, Va.

Hunt Seat Medal Final: 1st -- Beth Moorman, 14, Washington; 2nd -- Laurel Miller, 12, Sparks, Md.; 3rd -- Alison Firestone, 13, Waterford, Va.; 4th -- Alexandra Listrani, 13, Brookville; 5th -- Katie Huber, 15, Great Falls; 6th -- Emily Epstein, 14, South Salem, N.Y.