Kaiser Permanente said it has decided to build a new hospital on the current site of its giant medical center on Sunset Boulevard in Los Angeles. The 42-year-old hospital, Kaiser's largest in Southern California, needs a major renovation to meet new earthquake safety standards. In late 1996, Kaiser said it would close the hospital and send some surgical patients to St. Vincent Medical Center in Los Angeles. But that plan was scrapped in 1997 after Kaiser's membership exceeded estimates. Katherine Saux, a Kaiser spokeswoman, said the health maintenance organization has no timetable yet for the start of construction, no cost estimates and no details about the facility to be built.