I believe it started today with this blog entry at The Map Room, but suddenly there is a resurgence of interest in generating topographical maps in Google Earth. I’ve spoken about techniques for doing this in the past (here and here). However, let me share the easiest way to view US Topographical maps in Google Earth. This is a portion of a network link created by a company called 3D Solar which does USGS Topographical Overlays 
automatically. You just zoom in to an area of interest, wait for five seconds, and suddenly you have an overlay of a topo map. Just turn off the “USGSO topo maps” network link when you are finished using it. I recommend saving this one in your “My Places” for future use. For the full 3D Solar collection of network links (which also includes weather, NASA MODIS satellite images, and Landsat overlays as well), check out this GEC forum post.
usgs
Earthquake Monitoring
Earthquakes are happening around the world all the time, we just can’t feel all of them. The US Geological Survey (USGS) is constantly monitoring the Earth with sensitive instruments and for some time now has offered ways of sharing their data on the web through their Earthquake Hazards Program. In addition to RSS feeds, they introduced Google Earth KML network links which allow you to continuously monitor the status of earthquakes around the world. You can zoom in and look at the areas in the detailed satellite or aerial photos of GE. But, since most of the photos in GE are one or more years old, you won’t see evidence of that recent quake.
You have two main options off the USGS Earthquake Hazards page, plus a third option I found for just bigger quakes:
- Magnitude 1+ earthquakes, colored by age
- Magnitude 1+ earthquakes, colored by depth
- Magnitude 2.5+ during past 7 days
This is real-time data which can help you determine whether that shaking you felt really was a quake. One Google Earth Community member wrote how he experienced the earthquake data first-hand.