Earthquake Energy Converter

【Please read first】
This app does not give warnings or local shaking figures. You type a magnitude
and it converts that into an amount of energy, nothing more. It does not deal
with predictions, probabilities, where an epicentre is, or wave heights.

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◎ Magnitude 7.3 and 8.4 are 1.1 apart, and yet the energy differs by 45 times

Every step of magnitude multiplies the energy by about 31.6.
Two steps make it exactly a thousand.
Even a tenth of a magnitude, which sounds like nothing, is a factor of about 1.4.

This app is for seeing that difference as a number.

■ You type one magnitude

Enter 7.0 and you get:

・554,239,532 kWh
・about 476,879 tons of TNT equivalent
・1.9953 x 10^15 joules

Joules alone run to too many digits to mean anything, so tap the unit chips to
switch to kilowatt-hours or tons of TNT. The chart lists all three side by side.

■ Or start from a difference

How many times the energy for a given gap in magnitude:

・1 step → about 31.6 times
・2 steps → exactly 1000 times
・half a step → about 5.62 times

Take the larger one as 100 percent and it reads as a percentage instead:
one magnitude less is about 3.16 percent, two less is exactly 0.1 percent.

■ All of it comes from one formula

E (joules) = 10 to the power of (4.8 + 1.5M)

The relation goes back to Gutenberg and Richter, and the Japan Meteorological
Agency publishes the same form. A kilowatt-hour (3,600,000 J) and a ton of TNT
(4.184 x 10^9 J) are both defined quantities, so no source disagrees about them.

■ It is clear about which magnitude it uses

This app uses the JMA magnitude (Mj), the figure announced in Japan.
The moment magnitude (Mw) used internationally is defined differently, and the
two drift apart for the largest earthquakes.

The 2011 Tohoku earthquake was Mj 8.4 and Mw 9.0.
The well-known 9.0 is the moment magnitude.

There is no conversion between Mj and Mw here. The relation differs from one
earthquake to the next, so any single conversion table would simply be wrong.

■ Chart and notes

A chart from magnitude 1.0 to 9.5 in half steps, and the JMA magnitudes of
some major earthquakes in Japan (Tohoku 8.4 / Great Kanto 7.9 /
Noto Peninsula 7.6 / Great Hanshin 7.3 / Kumamoto 7.3 / Chuetsu 6.8 /
Hokkaido Eastern Iburi 6.7).

Nine notes in all: how magnitude differs from local shaking, where the formula
comes from, how Mj and Mw differ, how to read a TNT equivalent.

■ What is not in it

Local shaking figures, warnings, predictions, probabilities, focal depth,
wave heights, maps, a catalogue of past earthquakes, your location.

This app converts a magnitude into another way of saying it. That is all.

■ Features

・One screen, no settings page
・Negative magnitudes work, for tremors too small to feel
・Zero or negative energy prints a dash; a value outside the range it covers
comes with a line explaining that range
・Presets for common values and a five-item history

【No account needed】
The calculation runs on your device, and the figures you type stay there.

【Japanese and English】
The app follows your device language. Nothing to configure.

【Please note】
Every figure is the plain result of the formula above.
The size of the energy is not the size of the damage: the depth of the focus,
the distance from it, the ground and the time of day change everything.

【Privacy Policy】
https://cof745.github.io/jishin-privacy/