JPMorgan has performed better than most rivals during the credit crunch but on Monday it revealed tough credit conditions had forced it to take a $1.5bn writedown in July.
People close to the situation stressed that the latest capital raise was not a direct response to the new writedown.
Jamie Dimon, JPMorgan's chairman and chief executive, has often extolled the virtues of building a "fortress balance sheet" capable of withstanding the turbulent conditions in capital markets and the economy.
Financial institutions have been the biggest borrowers in the debt markets this year, accounting for about 36 per cent of all investment grade debt issued, according to CreditSights data. The activity from financial institutions this week highlights that many are still seizing opportunities to raise fresh debt.