LONDON (Reuters) - In a week when AI chipmaker Nvidia (NVDA) suffered the biggest one-day loss of value on record and the Federal Reserve said it was in no hurry to cut rates again, a few gauges underscore markets' vulnerability to big swings.

Investors and analysts said the sell-off in tech stocks this week, driven by the popularity of China's DeepSeek AI model, highlights the market ructions that can occur when heavy speculation meets unexpected bad news.

Here are five signals that highlight some of the tensions simmering.

1/HEAVY BETTING

Despite Monday's ructions investors remain bullish about U.S. tech and President Donald Trump's plans for tax cuts and deregulation, heightening risks of market gyrations if this widespread consensus proves wrong.

Short-term speculators have in recent months taken on more debt to magnify their gains, with levels of so-called gross leverage among hedge funds that trade U.S. stocks hitting their highest since 2010 in January, Morgan Stanley data showed.

Citi's equity positioning model, derived from futures contracts, shows traders are heavily betting on further gains for Wall Street's tech-focused Nasdaq 100 (^NDX).

"Everyone is sort of piled in. They're super optimistic," GAM chief multi-asset strategist Julian Howard said.

These trends are making some long-term money managers nervous, with JPMorgan attributing part of Nvidia's violent Jan. 27 drop to traditional asset managers selling out.

Kevin Thozet, investment committee member at Carmignac, said he had reduced exposure to U.S. tech stocks several days ago and added to positions that would profit if the Nasdaq fell, saying DeepSeek called U.S. tech-stock "exceptionalism" into question.

High-for-longer U.S. interest rates, he added, might prompt U.S. households, now heavily invested in stocks, to pull money out.

Analysis by the U.S. Office of Financial Research has also found strong correlations between retail investment in speculative assets, such as crypto-currencies and use of consumer credit, signaling last year's rate cuts fueled market gains.

2/ PRICES ARE NOT RIGHT?

The highest bond yields in years could also dent stocks' appeal as investors can now get returns of 4% or more on government debt.

One measure of the equity risk premium - the extra return investors can expect for stocks - dropped below zero in December for the first time since the aftermath of the dot-com bubble in 2002.

"When people talk about managing volatility amidst all this, one of the areas which does it really well is short-dated fixed income," said GAM's Howard.