SAN DIEGO – Hundreds of thousands of San Diegans and visitors gathered at viewing sites all around the city for the 12th annual Big Bay Boom saw Fourth of July fireworks all right: One spectacular 15-second blast of every firework caused by the most-talked-about technical malfunction since Janet Jackson’s Super Bowl performance.

The premature blast rocked the bay and downtown just before 9 pm Wednesday, rattling windows and doors with one loud boom, startling many residents.