NEW YORK — The nation’s largest banks are facing a fresh torrent of lawsuits claiming they sold shoddy mortgage securities that imploded during the financial crisis, potentially adding significantly greatly to the tens of billions of dollars the banks have already paid to settle other cases.

Regulators, prosecutors, investors, and insurers have filed dozens of new claims against Bank of America, JPMorgan Chase, Wells Fargo, Citigroup, and others related to more than $1 trillion worth of securities backed by residential mortgages.