Diablo Canyon quake safety key issue DIABLO CANYON State coastal panel has blocked proposal by PG&E to use air-gun method seen as hazard to marine life America's top nuclear regulator said Wednesday that if anyone wants to study in depth the offshore earthquake faults near PG&E's Diablo Canyon Power Plant, there is no substitute for the environmentally destructive tests blocked by California officials in November. [...] the tests, which involve blasting the seabed with air guns that create intense sound waves, are the only way to study the fault lines several miles into the rock, she said. PG&E has been under pressure from state officials to conduct more thorough seismic tests around Diablo, pressure that increased after the U.S. Geological Survey found another fault line near the plant four years ago.