The silence was suggested by the Luxembourg European Union presidency last week and is being held across the European Union, due to start in Britain at 12:00 GMT.
British Culture Secretary Tessa Jowell said the government hoped employers would allow their staff to observe the silence.
In the United Kingdom, flags will be flown at half-mast on government buildings and at Buckingham Palace. The royal household will observe the silence, a palace spokeswoman confirmed.
Also Wednesday, prayers will be said at churches, cathedrals and other places of worship throughout Britain. A spokesman for the Church of England said the silence would give people of all religions the opportunity to grieve for both the victims of the earthquake and those left homeless.
"This is a time for people to express, in the quiet of their own heart, their own feelings and their own grief about what has been a cataclysm," he said.