The ground has an inside. Slide a band of latitude across this earthquake archive. Its surface locations open into reported source depths: where the ruptures began, not how deep their waves travelled.
What is beneath a point?
Depth is a catalogue estimate and may be fixed or poorly constrained. Negative values are retained: the reference surface and location uncertainty matter. USGS uses a geoid reference, while contributing networks can use different depth references. A vertical whisker, when supplied, shows depth ± the source’s depthError; it is not a confidence interval calculated by this organism. Missing errors do not mean exact locations.
Only retained M6+ monthly catalogue records appear, at most 2,000 latest records. This is not all earthquakes, a hazard map, a fault reconstruction, or evidence of activity today. Empty regions may reflect the time window and magnitude threshold. Old cache entries without depth are counted but not plotted. Source depths outside −20 to 800 km are unavailable. Display clipping of uncertainty is marked in the details.
Reference lines at 70 and 300 km mark conventional earthquake depth classes, not rock boundaries. Depth and longitude have different units; this drawing has no uniform physical scale. The inherited PREM ray tracer is a separate surface-source teaching model and does not use these hypocentre depths.
USGS: earthquake depth · Depth reference