New York City ? JPMorgan Chase & Co. Inc. came to the rescue of Washington Mutual Inc. Thursday, buying the thrift’s banking assets after WaMu was seized by the Federal Deposit Insurance Corp. in the largest failure ever of a U.S. bank. This is the second time in six months that JPMorgan Chase has taken over a major financial institution crippled by bad bets in the mortgage market.

The deal will cost JPMorgan Chase $1.9 billion, and the bank said in a statement it planned to write down WaMu’s loan portfolio by approximately $31 billion. JPMorgan Chase, which acquired Bear Stearns Cos. last March, also said it would sell $8 billion in common stock to raise its capital position.

The FDIC, which insures bank deposits, said it would not have to dip into the insurance fund as a result of the seizure. There had been concerns that the fund, which took a big hit after the seizure of IndyMac Bank, could be depleted by a WaMu seizure.