Lots of @5.5 quacks @10km depth. Here is why they say 10km. In other words, they don’t know the depth so they tag it as 10km.
Why do so many earthquakes occur at a depth of 10km?
10 km is a “fixed depth”. Sometimes data are too poor to compute a reliable depth for an earthquake. In such a case, the depth is assigned to be 10 km. In many areas around the world, reliable depths tend to average 10 km or close to it. For example, if we made a histogram of the reliable depths in such an area, we’d expect to see a peak around 10 km. Thus, if we don’t know the depth, 10 km is a reasonable guess. We used to use 33 km. Increased understanding indicates that 10 km is more likely.
That’s agreeable to registering something. They are still a guess. There are also any number of seismic occurrences related to other events, like a volcano (many, many, many lower, 2.0 and below quakes). They know where they are but not always why they are.
Why not take advantage of this situation? Use the RFTG and remove problems in a precise manner, not leave any lingering radiation and maintain deniability.