Every earthquake the USGS recorded worldwide in the last 30 days, refreshed every minute. Around 10,000 events.
About
The USGS real-time earthquake feed: one row per event, with time (UTC), latitude, longitude, depth, magnitude and magnitude type, location description, event type and error estimates. It includes small local quakes (mostly in the US, where station coverage is dense) as well as significant earthquakes worldwide.
The file is regenerated every minute, so every download is different; it held 10,658 events when this page was written. The data viewer shows a snapshot taken when the page was set up.
The USGS publishes other windows (past hour, day, week) and magnitude thresholds on the source page, and the same data as GeoJSON.
Source and licence
U.S. Geological Survey Earthquake Hazards Program. A US government work, so in the public domain.