Reading jeffronicus' answer about how seismic stations record bomb explosions, particularly the reminder that the intensity of earthquakes drops by distance, made me start wondering what scale of earthquakes can be missed if they occur in just the right place, due to gaps in the observing network and the energy dropping too low by the time it reaches the nearest seismic stations.
Being a novice, I have no idea about typical resolution of instruments, the density/gaps in the observing network, nor whether earthquakes have other wave features that are more coherent and consistent than the impacts of weaponry explosions. But I figure there must be an intensity and location that would be currently undetectable? So how strong of an earthquake can be missed these days?
- For simplicity's sake, lets focus on fairly shallow earthquakes (in/near the crust?), as I'm figuring depth is an additional factor... and some quite strong movements thousands of km down go undetected!?