Date:  Wednesday, January 11, 1995
Time:  4:15 PM   Refreshments at 4:00
Location:  ERL 126

Investigations of Low Frequency (1 Hz to 30 Hz) EM Signals from
Underground Nuclear and Chemical Explosions - Applications to Treaty
Verification


Dr. Jerry J. Sweeney

Earth Sciences Division, Lawrence Livermore National  Laboratory (LLNL)


Abstract

Low attenuation of EM fields at ELF frequencies makes them attractive as
a possible means to detect underground nuclear explosions. During the
late 1980's an investigation was carried out by LLNL to see if ELF EM
signals from underground nuclear explosions coupled to the
earth-ionosphere waveguide and thereby could be used for world-wide
detection. We monitored 15 underground nuclear explosions with
multi-component EM sensors at distances ranging from 5 km to more than
10,000 km from surface ground zero. More recently, we have detected low
frequency EM signals from a large (1 Kt) underground chemical explosion.
In the talk I will discuss the equipment used and the results of these
field measurements and how they relate to the context of a low-yield or
comprehensive test ban treaty.