Millions of Californians were due on Thursday to simultaneously drop to the floor, clamber under tables and cover their heads for a minute or two of imagined seismic turmoil during the latest annual "Great ShakeOut" earthquake drill.
The event, first held nine years ago in the Los Angeles area, was organized by scientists and emergency officials as part of a campaign to prepare the region's inhabitants for a catastrophic quake that experts say is inevitable and long overdue.
The exercise has since expanded to encompass all of California and most other states, as well as some other countries, including Canada and Japan. In many places, entire school districts, colleges, workplaces and municipalities have registered to take part.