Cash flows into Japan equity funds last week were dominated by ETFs, with eight Japanese equity tracker funds pulling in $936.8m in the seven days to Wednesday, according to Lipper.
This figure accounts for almost all of the $955.9m total flows into Japan equity funds in that period.
Interest in the iShares MSCI Japan index fund, the largest ETF dedicated to the country, took off dramatically last week, peaking at almost 400m shares traded.
Bloomberg data shows this compares to the previous daily average of around 24m shares.
Despite early concerns though, such elevated volumes were not the result of panic selling. Lipper says iShares MSCI Japan attracted inflows of $860m in the week up to last Wednesday.
On Tuesday, when the fund's NAV dropped nearly 15% to six-month lows of $9.43, TrimTabs Investment Research reported inflows of $692m - the equivalent of over 10% of the ETF's total assets under management (AUM) in one day.
ETFs across all types of Japanese assets have seen trading volumes escalate in the aftermath of the country's devastating earthquake, after which the Nikkei plunged around 2,000 points.
According to media reports, activity on a number of Japan related ETFs on the morning of 14 March was so frenzied it triggered the US Securities and Exhange Commission's newly created short selling restrictions.
The SEC says it implements restrictions when a stock has dropped more than 10% in one day in order to prevent potentially manipulative or abusive short selling.
Currency ETPs providing long yen, short dollar exposure have also seen heightened interest from European investors, according to LaBranche Structured Products Europe head of sales trading Laurent Kssis.
Meanwhile in the US, the ProShares UltraShort Yen ETF has seen a surge of buying from investors betting against the yen's recovery.
With flows into Japan equity ETFs creeping up to $1bn, CitiGroup's Japan strategist Kenji Abe has estimated the Bank of Japan itself may have made ETF purchases worth up to $370m.
If accurate, the figures show BOJ using ETFs as a central tool in its asset purchase programme.
Whatever the motivation behind the trades though, the volumes seen over the past week demonstrate the critical role ETFs have come to play in investors' response to the situation in Japan.
Two global vehicles
'Further plug advice gap'
Must appoint separate CEOs and boards
Advisers do come out well
Will report to Mark Till