The Occidental Seismograph: https://weather.oxy.edu
U.S.Geological Survey: http://www.usgs.gov/
Specifics sites within the USGS :
- Earthquakes: http://earthquake.usgs.gov/
- Floods: http://water.usgs.gov/osw/floods/
- Volcanoes: http://volcanoes.usgs.gov/
- Hurricanes: http://coastal.er.usgs.gov/hurricanes/
- Landslides: http://landslides.usgs.gov/