Aftershock

## The feed

The USGS publishes every earthquake it records as a GeoJSON feed and updates it every minute. This piece reads the one for magnitude 2.5 and up over the last seven days: a few hundred quakes on a quiet week.

Your browser never asks USGS. It asks this site, and the site asks USGS at most once a minute for every visitor together, so nothing here sends your address to a third party.

## The map

The land comes from Natural Earth, drawn once into 120 columns of half blocks, so each cell is 3 degrees wide and each half block 2.5 degrees tall. It sits in the border grey, one step above the background, so the quakes are the only bright thing on it.

Each cell holds one glyph for its strongest quake: ░ under M4, ▒ under M5, ▓ under M6, and █ above. Earthquakes happen where plates meet, so after a week the bright blocks trace the Ring of Fire, the Mediterranean and the mid-ocean ridges.

Point at a block, or a row in the list, to read that quake. A click keeps it in the address bar, so a shared link opens on the same quake.

## The trace

The seismograph is the last 24 hours in 120 columns of 12 minutes, the same width as the map. Each column swings as far up as down for its strongest quake: one row for M2.5, one more for each magnitude above it.

A quake that arrives while the page is open glitches into the list.