Fears of a partial breakup of the euro zone are already causing deposit flight from banks in Portugal, Italy, Ireland, Greece and Spain -- sometimes collectively known as PIIGS -- said Jens Nordvig, head of fixed-income research at Nomura Holdings.

The deposit flight has already taken place, he told Bloomberg Television. It's not like we can pretend there is no problem nobody is going to notice. ... This is already happening.

Though a breakup isn't his central thesis, Nordvig believes it could happen if current austerity measures fail and leadership of governments in the 17-member euro zone lack the political will to push through fiscal integration -- central management of member states' combined finances.

Data from the Bank for International Settlement, an intergovernmental organization of central banks, for the end of 2011 shows bank deposits flowing out of PIIGS to core euro zone members France and Germany.

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Investors are, of course, uneasy over just the specter of a splintering of the currency union, as such an event could trigger the ultimate demise of the euro itself. If that were to happen, German assets denominated in a reintroduced mark would likely be worth far more than Greek assets denominated in a reintroduced drachma, hence the flight to German from Greece.

Some investors might want to avoid the mess of a possible euro breakup altogether and opt for an alternative currency such as the U.S. dollar.

Nordvig thinks that while fears of a euro breakup could temporarily boost German assets, actual dissolution of the zone could be extremely costly to Germany and cause its financial holdings to fall. If that scenario were to become reality, U.S. assets would likely emerge the safe haven for investors.

For now, the Nomura strategist recommends shorting the euro against against a basket of currencies consisting of the Japanese yen, Mexico's peso and Norway's krone.

Ever since new debt crises buffeted the euro zone in 2011, economists have been pondering the prospect of a breakup. Not everyone is as measured in his outlook as Nordvig, who sees the breakup scenario as a risk but not his central case.

Nouriel Rbouini, of Roubini Global Economics, who became famous for predicting the global financial crisis, thinks the only choice for debt-plagued countries such as Greece is to exit the euro zone. He believes the Greeks may do so by 2013 and that Portugal could be the next to go.