If you asked most seismologists for a brief summary of what they know about intermediate- and deep-focus earthquakes, they might write something like:

Unfortunately, most of the assertions in the above statement aren't strictly true; i.e., some are never true, some are true only sometimes, and some we aren't yet sure about. For example, in global earthquake catalogs about 25% of all earthquakes have reported focal depths exceeding 60 km (Table 1.1); the 75% that are shallower are hardly “nearly all.” Moreover, even for very large earthquakes with MW or mB larger than 8.0, those with focal depths of 60 km and more make up about a quarter of all events. Moreover, we shall see that not all deep earthquakes are associated with oceanic trenches; many important deep quakes occur as isolated events and not within planar groups. Whether deep quakes have higher stress drops and more impulsive source time functions is subject to debate.