Serious crime in Fairfax County dropped to its lowest rate in 10 years in 1982, with the most dramatic decrease in reported burglaries, police said yesterday.

The actual number of reported crimes decreased 11.6 percent between 1981 and 1982, from 26,706 to 23,600, the lowest number of crimes reported in the past five years. Reported burglaries and murders were down slightly more than 30 percent, police records showed. Motor vehicle thefts decreased by 19 percent and 1,664 fewer houses and businesses were burglarized, police said.

Reported rapes dropped 9 percent, robberies decreased 8.3 percent, aggravated assaults were down 6.5 percent and thefts dropped 6 percent, Fairfax police records show.

The lower crime rates reflect a nationwide trend that police and other law enforcement officials attribute to greater citizen participation in neighborhood crime-watch programs, more sophisticated police crime analysis work and the increasing number of individuals serving jail terms for serious crimes.

"Police leaders are doing more to get people involved in crime solving," said Police Chief Carroll D. Buracker. "Police are changing the macho attitude that we can do everything ourselves if we just have more policemen, bigger guns and faster cars. That's not the answer."

The rapid proliferation of neighborhood crime-watch groups is primarily responsible for the dramatic decrease in burglaries and auto thefts, he said. The number of neighborhood crime-watch groups has doubled to 300 community organizations in the past year, police said.

Almost every other metropolitan area police jurisdiction also is predicting an overall decrease in reported crimes for 1982, although only Fairfax County, Fairfax City and Alexandria have released figures.

Reported serious crimes dropped almost 27 percent in Fairfax City, while preliminary reports show a 6.2 percent decrease in crimes reported in Alexandria.

When compared to the increase in population in Fairfax County, the crime rate per 100,000 residents dropped last year to its lowest point in a decade, police said. Crime decreased from 4,398 crimes per 100,000 residents in 1973 to 3,983 crimes per 100,000 residents in 1982, police said.

"I am optimistic in believing we may have turned the corner as far as crime is concerned in Fairfax County," Buracker said. Buracker added, however, that he doesn't expect the dramatic decrease in reported crimes to continue. He said police expect the crime rates to level off in the next several years.