Terrifying. I program automated vibration analysis for blasting, and a very powerful explosive blast will feature particle velocities (the direct corollary for power) in the single-digit in/s range (~0.02-0.13 m/s) . This peak particle velocity is 20-150x higher than the peaks we see from the most powerful blasts we measure, if they're at all qualitatively comparable.

And of course, the earthquake energy source is many magnitudes larger and much, much further away, deep in the crust, with the wavefront already having passed through miles of solid rock. We measure blasts from at most a few hundred meters away.

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card_zero 5 days ago | parent [-]

in/s? Inches per second, or something else? One inch per second is the speed of an excited snail.

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netbioserror 4 days ago | parent | next [-]

This is the solid particles in the ground moving in place. As the wave passes through, any given volume of ground is displaced somewhat. In a balanced low-intensity wave, the soil or rock gets jostled around a bit. In a high-intensity balanced wave, the ground is yanked back and forth, potentially damaging foundations or buildings above the foundation. Particles will be displaced, but not permanently, with a net of 0.

In an unbalanced wave, the earth is permanently displaced in a particular direction. We can measure that net displacement in a particular direction using an anti-derivative if the total average velocity is nonzero (if we included negative velocities around a given axis). Earthquakes, of course, tend to have nonzero net displacement, and thus an extremely biased velocity waveform along a particular axis.

So in fact, the soil beneath you vibrating back and forth at 1 to 5 inches per second is not fun. At 118 inches per second? Catastrophe.

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Aachen 5 days ago | parent | prev | next [-]

Must be inches per second because 1–10 of those is 0.025–0.25 m/s so that matches the parentheses

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csours 5 days ago | parent | prev [-]

in soil, not air.

	▲	card_zero 5 days ago \| parent [-]
		Yikes, I see.