The physics of sound wave cancellation was fundamentally matching whether dealing with a buzzing organ pipe or an earthquake tearing through a mountain.
Giles Croft stood on the gravel riverbank three hundred yards upstream from the Great Sky-Line Viaduct, checking the depth gauge on drilled shaft number twelve.
Twenty-four deep upright holes, each four inches in width and eighty feet deep, had been drilled into the solid mountain stone along an exact curved curve calculated by Toby Karr.
Inside each hole, Master Borin’s tunnel diggers had packed thirty pounds of high-speed nitro-water-setting blasting compound, wired to an electric rotary firing sequencer.
“The principle is simple destructive wave interference,” Giles explained. His voice was calm over the rumble of the approaching tremor.
“A ground-shaking shear wave is a clockwork pressure wave moving through an elastic medium.
If an earthquake wave arrives with a positive crest, and we trigger a counter-blast that creates an equal and opposite negative pressure trough at the exact same split second, the two waves cancel each other out.”
The building behind the sound interference array had needed four hours of relentless exact math.
