USGS ComCat Β· Real-Time Seismic Β· US States Β· Magnitude Analysis
π AFTERSHOCK
Real-time earthquake monitor pulling every measurable shake from the USGS Earthquake Hazards Program ComCat API β M1.5 and up, worldwide, updated hourly via GitHub Actions and from the USGS live feed every two minutes. 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.
Pick the US, any state, any country or region. Each view is compared with ten years of normal at the magnitude its networks reliably catch (M2.5+ for states, M4.5+ for countries), with aftershock sequences checked against Omori’s and BΓ₯th’s laws, a GutenbergβRichter b-value, where the energy went, and what the depths say.
USGS 3DEP Lidar Β· USGS Mine Maps Β· Melones Fault Zone Β· Tuolumne County
βοΈ Mother Lode
Gold country with the trees and buildings stripped away. Bare-earth lidar, streamed from the USGS archive, shows the ground the miners left behind: the limestone pinnacles washed bare at Columbia, the stepped waste dumps and drowned pit of the Harvard mine at Jamestown, the old tailings along Woods Creek that now sit out on Don Pedro Reservoir.
On top of it, every shaft, adit, prospect pit and tailings pile the USGS drew on its old topo maps across the county, and the named mines from its mineral database, each with a short, sourced story.
| 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 TΕhoku earthquake was M9.1. Triggers tsunamis. |
Each full magnitude step releases ~31.6Γ 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 β 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 β M6.9, 15 seconds, 63 dead β was the event that made this abstract geology personal. The fault does not announce itself. The data never lies.
Alaska Is Always First
Count every quake down to M1.5 and Alaska is always first, by a margin that isn't even close β partly because it is so active and partly because it is so well instrumented. Compare at M2.5+, where every state is recorded fairly, and Alaska is still first. 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 β the most powerful ever recorded in North America.
The Cascadia Subduction Zone β offshore of Washington, Oregon, and northern California β 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.