The population of Metropolitan Tokyo is similar to:
The combined populations of metro NYC and metro LA.
The population of the entire State of California.
The combined populations of Croatia, Guyana, Qatar, Norway, Switzerland, New Zealand, Mongolia, Kosovo, Estonia, Fiji, Uruguay, Iceland, and the Bahamas.
As you may already have guessed, all of these statements are true.
Tokyo lies near the Boso Triple Junction, a geographic point off the coast of Japan where the North American, Pacific, and Philippine Sea Plates meet. Small earthquakes occur relatively frequently in Tokyo. The last major quake to strike the city however, a magnitude 8.3 event that killed an estimated 142,000 people, occurred way back in 1923.
Science Link: https://pubs.usgs.gov/gip/dynamic/dynamic.html