SANTA ANA, Calif.—Ruth Ann Moriarty, considered the matriarch of one of Orange County’s most prominent families and a noted philanthropist in her own right, has died at the age of 99. Moriarty was the older sister of Henry T. Segerstrom, who developed South Coast Plaza and the adjacent Segerstrom Center for the Arts in Costa Mesa. She died Tuesday, Jan. 4, two weeks shy of her 100th birthday. “We are deeply saddened that our mother, Ruth Ann, is no longer with us, but are very grateful to have been part of the long and vibrant life that she shared with us and others,” her children said in a joint statement issued Friday, the OC Register reported. “We will always treasure her incomparable legacy of service to communities in need.” The Segerstrom family emigrated from Sweden in 1882. Moriarty’s grandparents worked in the dairy industry before becoming one of the largest …