Nov 9, 2026
One earthquake gets one magnitude but many intensity values. Here is how USGS rates shaking town by town, and why a nearby moderate quake can feel stronger than a distant big one.
Nov 9, 2026
The Yellowstone Volcano Observatory reports earthquakes, ground motion and hydrothermal activity every month. Here is what those numbers mean and what USGS says about the chance of an eruption.
Nov 9, 2026
Kīlauea's summit eruption comes in short bursts of lava fountaining separated by pauses of weeks. This is how the Hawaiian Volcano Observatory reports each stage.
Nov 9, 2026
After a strong earthquake, USGS publishes the odds of more shaking. Here is what foreshocks, mainshocks and aftershocks are, how long sequences last and how to read the forecast table.
Nov 9, 2026
Nine of the ten largest earthquakes in US history struck Alaska. Here is the full ranking from the USGS catalog, with the largest outside Alaska and what the official records say about each.
Nov 9, 2026
California has hundreds of active faults, but a few carry most of the attention. Here is what the USGS and the California Geological Survey say about them, with the official 30-year odds by region.
Nov 9, 2026
A tsunami starts when a large volume of ocean water is suddenly pushed out of place. Earthquakes do that most often, but only certain kinds, and landslides and volcanoes can too.
Nov 9, 2026
Every USGS volcano update starts with two labels. One is written for people on the ground, the other for pilots, and they usually change together.
Nov 9, 2026
Depth tells you how far below the surface an earthquake started. Here is how USGS classifies it, how it is measured and why early reports often show exactly 10 km.
Nov 9, 2026
The USGS event page packs a lot into a few lines. Here is what automatic and reviewed mean, how the location text is built, what PAGER colors stand for and why the tsunami flag is not a warning.
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