Seisma
The Gutenberg–Richter Law Physics
Size guide S–5XL · inches
Seisma strikes the fault line and sends out a staircase of cracks: many small ones, few large ones, each step rarer than the last.
The Physics
Beno Gutenberg and Charles Richter found in 1944, for California earthquakes, that the number of quakes at or above a magnitude falls off exponentially with magnitude. The constant a sets a region's overall activity; the slope b is typically close to 1, so each step up in magnitude is about ten times rarer.
log₁₀ N = a − bM
- N: number of quakes of magnitude M or more
- M: magnitude
- a: regional activity constant
- b: slope, usually near 1
Gutenberg & Richter, “Frequency of earthquakes in California”, Bull. Seismol. Soc. Am. 34, 185 (1944).
Honest caveat: b is not universal: about 0.8–1.2 is a common range for tectonic quakes, and volcanic or induced swarms can differ more. The power law is often linked to self-organised criticality, but that is debated.
On the shirt
Front: Seisma, the pixel-art character, with “TEN TIMES RARER”. Back: the Gutenberg–Richter law, the ten-times-rarer rule, the regional range of b and the 1944 paper. Printed on a unisex tee.
Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days
Details
Size & fitS–5XL
Unisex heavy cotton (Gildan 5000), classic fit.
| Size | Width | Length | Sleeve |
|---|---|---|---|
| S | 18 | 28 | 15.1 |
| M | 20 | 29 | 16.5 |
| L | 22 | 30 | 18 |
| XL | 24 | 31 | 19.5 |
| 2XL | 26 | 32 | 21 |
| 3XL | 28 | 33 | 22.4 |
| 4XL | 30 | 34 | 23.7 |
| 5XL | 32 | 35 | 25 |
For scale: size M is 20 in (50.80 cm) wide, about 3.143 × 1034 Planck lengths (lP = 1.616255 × 10−35 m). A tape measure is quicker.
Measurements in inches, ±1.5 in tolerance.
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Returns & replacements21 days
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Field notes
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