PGS: monitoring nuclear explosions through seismicity

The April meeting of the Potomac Geophysical Society will be held April 19th at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

This month’s talk is:

Title: A Review of the Cavity Decoupling Evasion Scenario: Implications for Seismic Monitoring of Underground Nuclear Explosions

Speaker: John R. Murphy, SAIC

Abstract: The concept that it might be possible to significantly reduce the seismic signal radiated by an underground nuclear explosion by detonating the device in a sufficiently large air-filled cavity (i.e. cavity decoupling) was first proposed publicly by A. L. Latter of the U.S. at the 1959 Nuclear Test Ban Conference in Geneva, Switzerland. Despite the fact that the concept has been around for more than 50 years, it continues to pose the greatest challenge to effective seismic monitoring of possible clandestine underground nuclear tests. In this talk, Jack will present a brief overview of the cavity decoupling evasion scenario and discuss the results of some new theoretical simulations that he and his colleagues have been conducting to evaluate effectiveness of nonspherical cavities.

Bio: Jack Murphy is a long-time member and former officer of PGS. Jack received his geophysics degree from Boston College. Mr. Murphy is a Chief Scientist at SAIC and has had more than 40 years of experience as a research seismologist. He is an internationally recognized expert in the modeling and analysis of seismic signals produces by explosion sources.

New Meeting Room and Dining Arrangements: We now meet in the glassed-in room at the back of the main dining room—The Fife and Drum. We order individually from the Club menu, which has a nice variety of dinner offerings. We pay a single bill (I pay it with my Officers Club credit card), so we collect at least $25 from each diner with the agreement, that if one orders more than $20 in food and drink, he adds the amount over $20 to his contribution. The $5 overcharge goes to the Room Fee, Tax, Gratuity, and the Speaker’s Dinner. We collect on the Honor System. We did this for the first time in September, and it worked well. This room change and use of the menu have greatly reduced the loss that we have incurred in the past for having fewer than 20 people dining, and the change has preserved the viability of using the Officers Club for our meetings.

Reception at 6:00. Order Dinner at 7:00. Talk at 8:30 PM. Please note that the meal orders will be taken at 7:00. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001 or via E-mail at If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email to

Robert B. Fraser
Cell: 703-624-3965
Home/Fax: 540-888-3001



One response to “PGS: monitoring nuclear explosions through seismicity

  1. Pingback: Nuclear Calendar — April 16, 2012 | FCNL

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