Actually this (mini?)crash started at 08:00 07:00 am local time in China.  It may be that the banks re-opened after the New Year's holiday week, and money withdrawals became possible again; so that investors who were disappointed with Bitcoin's performance over the holidays immediately started dumping and taking the cash out.

EDIT: fixed the time zone (UTC+08:00 not UTC+09:00).  Would banks open at 07:00? Perhaps it is people going back to work and using their computers there?  Or LAN houses opening?