A massive explosion in Buenos Aires killed the 15-year-old daughter of Argentina's second-ranking admiral yesterday in an apparent revival of political terrorism just as the military rulers were taking a first step toward eventual return of civilian rule.

Vice Adm. Armando Lambrushchini, 52, who is to assume command of the navy and join the ruling junta this fall, was unhurt in the blast near his apartment although he was there at the time.

The explotion came about at 2 a.m. in an adjoining apartment building which was destroyed. An 83-year-old woman also was killed and at least 10 persons were injured as the blast shattered glass fronts along the fashionable street near the center of Buenos Aires.

Although several thousand Argentines have died in warfare between extremists of the left and right over the past six years, the pace recently had slowed to the point of having no recorded fatalities since a policeman was killed defusing a bomb May 10.

The government of President Jorge Videla declared recently that it had virtually defeated Marxist guerrilla groups that have assassinated scores of police and military officers. Civil liberties often were ignored in the government's campaign, with human rights groups accusing the military of killing and torturing thousands of persons.

Official U.S. support of these charges has strained American ties with Argentina and embittered those Argentines backing the antiterrorist effort of the military. The Associated Press quoted a woman at the scene of the blast yesterday as saying:

"There are still a few of [the terrorist] left. They have no respect for human rights. The people sleeping in those buildings have no human rights."

This week's first step toward return of civilian rule came with the retirement Monday of President Videla as commander of the army.

Formally, Argentina is now ruled by a civilian - and the change is more than symbolic. Since the military seized power in 1976. Videla has weilded power not so much as president but as the man at the pinnacle of the chain of command in the preponsderantly powerful army.

Yesterday, Gen. Roberto Veiola assumed that key post. Videla will serve at the behest of Viola, Air Force Gen. Orlando Agosti and Navy Adm. Emilio Massera. The result is to dilute the concentration of power.

All four officers have indicated that this step, made possible by the decrease in terrorism, will be followed by others bringing wider civilian participation in government.

Of the current junta, however, only Massera has persistently publicized a position in favor of human rights and rekindling of political activity that is now banned. He must retire in September and is to be replaced by Lambruschini.

Thus, while it seems clear that the admiral was the target of yesterday's explosion - the owner of the apartment house said two men claiming to be police had her let them into the unoccupied apartment near Lambruschini's Monday night - it is less clear why.

No group claimed responsibilities for the explosion, and U.S. and Argentine officials here predicted that since the daughter rather than the admiral was killed, those responsible were likely to remain silent.

These officials felt, however, that the purpose was to harden the military against moderating their rule. Guerrilla groups have long made clear that they feel their longterm objective of socialist revolution is served by provoking the military into arbitrary actions.

Late in 1975, a similar powerful explosion rocked the downtown army headquarters. It went off near Viola's office who was then chief of staff, but he was away at the time. The blast occurred during a period of intense agitation over the failure of Isabela Peron, then president, to maintain stability after the death in office of her husband Juan.

Peron himself had only mitigated the factional warfare that had forced the military to wind up its last stay in power in 1973. At that time, the navy was a prime target of the guerrillas because of the killing of 16 of their members imprisoned at a navy base.

Several figures associated with the killings, including an admiral and the civilian who was interior minister at the time, were gunned down in 1973-74. Another admiral was kidnaped and released only after acknowledging in a statement made public by his captors that the guerrillas' deaths "were a sad affair" for the navy.

Lambruschini, however, had no known connection with the affair and the People's Revolutionary Army that carried out the guerrilla attacks against Navy officers has all but disappeared in the face of the military crackdown.