Why do some earthquakes have negative depths?

Why do some earthquakes have negative depths?...

Detailed Description

The depths of earthquakes beneath Hawaii are now reported with respect to the geoid, or sea level, and are known as "geoid depths." This figure illustrates how two earthquakes can have negative or positive depths depending on whether they are above or below sea level. The previously used "model depths" are shown for comparison. (USGS figure.)

Details

Image Dimensions: 960 x 324

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