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Comment by dustintrex | Hacker News Reader

With all due respect, you're making that sound a lot worse than it is when compared to places that are genuinely earthquake-prone. Australia is extraordinarily stable in geological terms and well outside the Pacific Ring of Fire, which frequently generates earthquakes of magnitude 9+. And since the magnitude scale is logarithmic, M9 is 1000x more powerful than M6.

Yes, magnitude does not equal seismic intensity and all that, but Australia has never in recorded history experienced a M7+ earthquake, while Japan alone experiences one every couple of years and New Zealand has had 4 in the last 5 years.

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> M9 is 1000x more powerful than M6

I assume you're using moment magnitude [1] since it's the most common measure. In fact every 2 integers is a 1000 times increase [2] so M8 is 1000 times more powerful than M6.

[1] https://en.wikipedia.org/wiki/Moment_magnitude

[2] https://en.wikipedia.org/wiki/Moment_magnitude#Definition

Whoa, whoa, ⅔ log₁₀? I learned the Richter scale which is log₁₀ and didn’t realise that wasn’t what was used any more, and I’m pretty sure that’s a normal misconception.

https://en.wikipedia.org/wiki/Richter_magnitude_scale:

> Because of various shortcomings of the ML scale, most seismological authorities now use other scales, such as the moment magnitude scale (Mw), to report earthquake magnitudes, but much of the news media still refers to these as “Richter” magnitudes. All magnitude scales retain the logarithmic character of the original and are scaled to have roughly comparable numeric values (typically in the middle of the scale).[citation needed]

Not to nit, but Richter is also not just log_10: a single point increase is ~32x more energy. This is due to the relationship between energy and shaking amplitude:

> The energy release of an earthquake,[27] which closely correlates to its destructive power, scales with the 3⁄2 power of the shaking amplitude[why?]. Thus, a difference in magnitude of 1.0 is equivalent to a factor of 31.6 in the energy released.[28] The elastic energy radiated is best derived from an integration of the radiated spectrum, but an estimate can be based on mb because most energy is carried by the high frequency waves.

¯\_(ツ)_/¯

Sounds like what they teach casually is simplified well past the point of accuracy and possibly even particular usefulness.

I mean, it’s still logarithmic. What’s a constant among friends?

All my algorithms are O(1).

Dropping constant factor does not seem that important to be honest. The important thing to be exposed to/take away was the logarithmic behaviour. I'm sure if you want to go be a seismologist you will quickly learn all the details. If people realise the magnitudes are exponentially more damaging , then isn't that sufficient for the general audience?

I never claimed Australia has it bad. I took this from Geoscience Australia's website on why Australia actually gets earthquakes.

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