BEIJING — Wednesday marks the second anniversary of China's worst disaster in a generation, the Sichuan earthquake — and a painful milestone for the families of the 17,921 people still recorded as missing.

Chinese law says relatives can apply two years after a disaster to have their loved ones registered among the dead. Not many are expected to do so. It's a choice that offers some minor financial compensation and a mix of closure and fresh pain.

"It will be like exposing their scars another time," said Gao Guizi, who runs the Sichuan 512 Relief Service Center, which helps coordinate the aid groups working with quake survivors.

Some mental health workers say the families of the missing carry a more difficult burden than those of the dead.

"They still have feelings that their loved ones could come back," said Hai Lan, a Red Cross mental health crisis expert. Her team is the only one to have stayed in the quake-hit region in southwest China over the past two years. "Emotionally, it's harder to deal with. The people who know for sure, it's much more easy."

As families come forward, the official death toll — 68,712 as of the last count a year ago — will climb as the claims are verified. The provincial government has said it will take a year after relatives apply for such deaths to become official.

Sichuan officials are expected to update the number of dead and missing at a news conference Wednesday.