National Strong-Motion Program http://nsmp.wr.usgs.gov/
USGS program has the primary Federal responsibility for recording each damaging earthquake in the United States on the ground and in man-made structures in densely urbanized areas to improve public earthquake safety. The program maintains a national cooperative instrumentation network, a national data center, and a supporting strong-motion data analyses and research center in support of this responsibility.
Society of Exploration Geophysicists http://www.seg.org/
SEG hosts 2 monthly publications and yearly trade shows, at the international, national, and regional level. The major organization for geophysicists involved in exploration and production of hydrocarbons.
