The chairman of the D.C. board of elections said yesterday that apparent irregularities have been found in petitions and voter registration forms filed by sex magazine publisher Dennis Sobin and several of his supporters who are trying to get their names on the Sept. 9 Statehood Party primary ballot.

Chairman Edward W. Norton said during a hearing that the findings of a board inquiry may be turned over to the U.S. attorney's office for review.

"I don't say this is a trivial matter . . . . Somebody has been abusing the process," Norton said, adding later that the board would "pursue this with serious vigor."

A person convicted of fraudulently filing election documents would face a fine of up to $10,000 and one year in jail, according to the board's legal counsel.

Sobin, a candidate for mayor, and his slate of three candidates for D.C. Council seats, switched their party registration from Democratic to Statehood on the last day to file nominating petitions.

Several longtime members of the D.C. Statehood Party contend that the petitions were improperly filled out and are questioning the validity of several of the signatures.

"There is clearly forgery here," attorney Daniel Schember said during the board hearing. Schember represents the longtime Statehood Party members who are challenging the petitions filed by Sobin and his so-called "Sexcrats" slate in an effort to keep their names off the ballot.

Paul H. Kunberger, the lawyer for one of the slate candidates, Michael Jarboe, said he had not received adequate notice to prepare a case. He persuaded the board to schedule another hearing on Tuesday before taking any action.

"What we have here minimally is inconsistent signatures," Norton said after Statehood witnesses produced various documents, including postal change of address forms, mail registration applications and petition signatures that purported to be by the same person.

Witnesses challenging the slate included Alexa Freeman, a Statehood Party member and a staff attorney for the American Civil Liberties Union, and Brent Dillingham, a private investigator.

Sobin, who ran for mayor in 1982 as an independent, said in an interview, "I certainly welcome the investigation . We have determined the reason for the inconsistencies and will present our case on Tuesday."

Sobin said the signers would vouch for their signatures and explain that the differences were due to the time of day and various ailments suffered by them at different times.

Sobin suggested that private investigators used by the Statehood Party had misrepresented themselves as working for the election board in efforts to determine the legal addresses of some of his candidates and petition signers.