SEAL BEACH : Underground Blast at Base Moved to Friday

The big blast residents expected Wednesday from the Seal Beach Naval Weapons Station fizzed.

The planned underground explosion at the weapons base, part of an experiment by the U.S. Geological Survey to map hidden fault lines, has been delayed until 1:30 a.m. Friday, according to weapons base spokesman Richard Williamson.

Researchers originally planned to begin the series of underground blasts in Seal Beach and continue northeast into Los Angeles County, through the San Gabriel Mountains and into the Mojave Desert. But the explosions began in Barstow early Wednesday morning instead.

“It’s just logistics,” said Jim Mori, a seismologist for the U.S. Geological Survey in Pasadena. “For whatever reason, the shooters decided to start at the other end.”

The experiment began Oct. 13 with a series of undersea bursts of compressed air between Long Beach Harbor and San Clemente Island. There will be 60 underground explosions in all from Barstow to Seal Beach. Researchers are recording sound waves generated by the blasts on hundreds of seismographs to try to predict which areas are most vulnerable to major earthquakes.

Seal Beach residents have raised concerns about the safety of setting off an explosion at the Naval Weapons Station, where high-powered ammunition is stored. But weapons base officials say the ammonium nitrate explosives used in the test will be detonated 140 feet below ground, well away from ordinance storage areas.

At most, scientists say Seal Beach residents will hear a dull thud from the Friday morning explosion. “It will be equivalent to a construction blast,” Mori said. “In Southern California, things are always shaking a little bit.”