(Our weekly analysis of the wild world of cryptocurrencies. Repeats for additional subscribers)

By Lisa Pauline Mattackal

Sept 6 (Reuters) - Bitcoin's been called a lot of things. Buzzy, beguiling, baffling, even bogus. But never boring.

Yet, of late, it's been eerily subdued.

The king of the swingers has been uncharacteristically treading water for days at around $20,000 and hasn't ventured far beyond that since June.

That spells trouble for traders and exchanges that profit from bitcoin's wild price lurches, and is opening the door to its archrival ether which is preparing to up its crypto game by moving to a meaner and leaner blockchain.

"Bitcoin is not dead, it's just boring at the moment, so traders are already looking for alternatives," said Martin Leinweber, digital asset product strategist at MarketVector.

Bitcoin's average 30-day volatility - a measure of how its price varies over a set period of time - has slumped to 2.7% from over 4% in early July, according to data firm Coinglass.

That number has stayed firmly below 5% in 2022, even in the most turbulent months of the "crypto winter" of depressed prices - a departure from the past five years when even periods of lower volatility were followed by spikes as high as 7%.

Similarly, an index from CryptoCompare, which uses bitcoin futures contracts to work out how far prices are expected to change, stands at just over 77, down from above 90 at the start of the year.

Bitcoin has seen periods of reduced volatility in the past, often during periods of depressed or falling prices, with its price swings often coming back as trading activity picks up.

This slump may be different, though.

"This has been a relatively long period of decreased volatility, it's now beyond anything we've seen in even 2019 where these levels lasted around a quarter to a quarter-and-a-half," said Stéphane Ouellette, CEO at crypto derivatives provider FRNT Financial.

ETHER OVERDRIVE

Leinweber at MarketVector pointed to an uptick in trading for ether and its derivatives as a side-effect of bitcoin's subdued volatility.

Indeed, the price of ether - the No.2 crypto with a market cap of roughly $190 billion versus bitcoin's $380 billion - has risen 50% since the start of July while bitcoin has been flat.

Ether doesn't offer more price drama; it is far less volatile, with its highest level being just over 2% in March 2020 during the worst of the COVID market rout, according to data firm Messari.

Yet it is soaking up a lot of the crypto buzz at the moment as it stands on the verge of its "Merge", expected to finally happen later this month, when it undergoes a radical shift to a system where the creation of new ether tokens becomes far less energy-intensive.