A balanced response

White House reaction to the South Korean jetliner tragedy has unfolded largely with the balance of moral outrage and calculated countersteps to hold the incident in per-spective.

President Reagan labeled the downing of the civilian aircraft by the Soviets ''the Korean airline massacre'' and an ''act of barbarism'' in his Monday night address. He set curbs on cultural, scientific, and diplomatic ties between the Soviet Union and the United States. The West's response carried over to the United Nations Tuesday, as the administration sought a coordinated outcry against the Soviet Union.

These are second-tier reactions by the West. None are confrontational. They fall well short of tampering with the first tier of security and arms control issues which are of paramount interest to East and West alike. They are rebukes, warnings.

Notably not done was cancellation of US-Soviet grain agreements, or any tainting of the American welcome to Soviet athletes for next summer's Olympic Games in Los Angeles. These would have been Jimmy Carter-like actions, and the Reagan team want to avoid any comparisons with the previous administration's futile efforts at modifying Soviet behavior.

Apart from the difference between the West's and the Soviets' apparent valuation of human life, the most disturbing revelation in the airliner tragedy is that the Soviet command structure may simply not be up to handling a crisis of this sort. Downing the aircraft was a serious mistake. At a time the Soviets are trying to sow discord among Western allies, it provokes a unified Western response. Combined with the willingness of the Soviet military to take actions that are blunt and inhumane, the dribs and drabs of Soviet official explanation have worsened the Soviets' position in the eyes of the world. The Soviets took five days to admit they had shot down the plane.

Unanswered questions remain. What is the use today of civilian aircraft overflights for military surveillance? How did hours pass with the South Korean aircraft heading over Soviet territory without notice or an immediate Western attempt to clarify its status? Was it a computer failure or some other cause that sent the aircraft on its fatal course? Answers must still be found.

The Reagan administration says the goal in its response is to focus world and domestic attention on ''the nature of the Soviet beast'' - a point Reaganites have made all along. ''Who are they?'' one Reagan insider asks. ''We really have to ask that before we focus on the details of the event.''

At the same time, the administration assumes the Korean jetliner tragedy will have a relatively short life as a headline commanding event. Emotionally potent as it may be, it will lack the numbing endurance of, say, the year-long Iranian hostage incident. With arms negotiations proceeding, and a US presidential election race about to start, the shootdown will ''remain a subject of continuing allusion,'' insiders say.

The administration clearly wants to avoid tying itself too closely to the jetliner incident, the way President Carter became embroiled in the Iranian hostage episode, and making any specific outcome a test of Reagan's competence. At the same time, the White House is using the event for other purposes, chiefly to press Congress for greater military spending to contain the Soviets.

Fortuitously, the jetliner incident enabled President Reagan to return from his August vacation in California on an urgent business note. Augusts have been awkward months for this administration. The White House has been preparing the stage for a Reagan reelection bid. Reagan's tough words about Soviet behavior in downing the defenseless aircraft should help him hold the support of his own right. The Democrats can do little but back the President in the affair.

The risks are that details of the overflight might eventually compromise the West's position, that a rhetorical escalation might jeopardize East-West security talks. But so far the line between calling the Soviets for their act and excuses, and safeguarding security issues, is apparently being kept in sight.