JPMorgan Chase & Co. trader Bruno Iksil, known as the LondonWhale because his bets this year were so large, has been aleviathan of a risk-taker since at least 2010, a person withknowledge of the matter said.

Iksil's value-at-risk, a measure of how much a trader might losein one day, was typically $30 million to $40 million even beforethis year's buildup, said the person, who wasn't authorized todiscuss the trades. Sometimes the figure, known as VaR, couldsurpass $60 million, the person said. That's about as high as thelevel for the firm's entire investment bank, which employs 26,000people.

Investigators are examining how long senior executives knewabout Iksil's swelling bets at the chief investment office beforelosses approached $2 billion. One focal point is why the formulaused to calculate Iksil's VaR was altered early this year, cuttingthe reported risk by half. The change followed an internal analysisin late 2011 and was approved by top risk executives, said a personclose to the bank. About the same time, half a dozen managerstypically involved in such decisions moved to new jobs.