USGS ComCat · Real-Time Seismic · US States · Magnitude Analysis
🌍 AFTERSHOCK
Real-time U.S. seismic activity monitor pulling every measurable shake from the USGS Earthquake Hazards Program ComCat API — M1.5 and up, worldwide, updated every six hours via GitHub Actions. A dark cinematic map where earthquake dots are sized and colored by magnitude, from tiny green pinpoints for microseismicity through yellow, orange, and red into deep red and purple as the energy scales up. A magnitude 7 sits on the map like a bruise.
Click any US state for a full breakdown: event count, largest magnitude, average depth, magnitude distribution chart, most recent events list. Click any earthquake dot for magnitude, depth, time elapsed, and a direct USGS event link. Two filter controls — time window (1D to 30D) and magnitude slider — wire through everything simultaneously.
| Magnitude | Energy Equivalent | What It Feels Like |
|---|---|---|
| M 2.0 | Small construction blast | Rarely felt. Detected by instruments only in most cases. |
| M 4.0 | ~1 ton of TNT | Felt indoors. Rattles dishes. No significant damage. |
| M 5.0 | ~32 tons of TNT | Widely felt. Minor damage to poorly constructed buildings. |
| M 6.0 | Hiroshima bomb | Destructive in populated areas. The Napa earthquake (2014) was M6.0. |
| M 7.0 | 32 Hiroshima bombs | Major earthquake. Loma Prieta (1989) was M6.9. Serious damage over large areas. |
| M 8.0 | 1,000 Hiroshima bombs | Great earthquake. The 1906 San Francisco earthquake was estimated M7.9. |
| M 9.0 | 32,000 Hiroshima bombs | Massive. The 2011 Tōhoku earthquake was M9.1. Triggers tsunamis. |
Each full magnitude step releases ~31.6× more energy than the step below it. The Richter scale is logarithmic. AFTERSHOCK expresses total seismic energy as a Hiroshima equivalent to make this concrete.
The Melones Fault Zone
The Melones Fault Zone is a major tectonic suture running through the western Sierra Nevada foothills of California — a boundary between ancient terranes accreted onto the North American continent during the Mesozoic. Tuolumne County sits squarely in this geology. The hills around Sonora and Groveland are crumpled and compressed, the rock record of collisions that happened hundreds of millions of years ago.
The 1989 Loma Prieta earthquake — M6.9, 15 seconds, 63 dead — was the event that made this abstract geology personal. The fault does not announce itself. The data never lies.
Alaska Is Always First
The AFTERSHOCK national leaderboard ranks US states by seismic event count, and Alaska is always first — by a margin that isn't even close. The state sits at the convergence of the Pacific and North American plates, one of the most seismically active regions on Earth. The 1964 Good Friday earthquake was M9.2 — the most powerful ever recorded in North America.
The Cascadia Subduction Zone — offshore of Washington, Oregon, and northern California — is the other major threat in the region. A full-margin rupture would produce a M9.0+ earthquake and a tsunami reaching the coast within minutes. AFTERSHOCK watches the microseismicity along that margin constantly.