Chapter 4: An Illustration of the
New Challenge
Chapter 4 Footnotes
1. The U.S. Geological Survey´s PDE lists the location, depth, and magnitudes of seismic events recorded around the world.
2. The listing also indicates that 51 P arrivals were used in the location, that the depth was determined from two or more compatible pP phases, and that the 90% confidence intervals for location and depth are eight km.
3. Note that an error of 27 minutes in time would change the location to the other side of the world, as P-waves travel at a velocity of several kilometers per second. In addition, the difference between a magnitude 5.6 seismic event and a 4.6 event is substantial. A magnitude 5.6 event releases approximately 30 times more energy than a 4.6 event.
4. Given the past conflicts between Pakistan and India, it is possible that Pakistan may have been using the event to draw attention to India´s nuclear capabilities. See for example "On the Nuclear Edge" by Seymour M. Hersh, The New Yorker, March 29, 1993, p.56-73.
5. Note that this practice has been changed so that data gaps no longer occur.
6. There are two main types of surface wave, Rayleigh waves and Love waves. They differ in their particle motion. While Rayleigh waves can be detected by seismometers sensitive either to vertical or horizontal motion of the Earth's surface, Love waves are only detected by seismometers sensing horizontal motion.
7. Previously, seismic observatories had ´short-period´ and ´long-period´ sensors to record ground motion. This arrangement, however, left much of the signal lost or distorted. A desire to obtain a more faithful record of ground motion led scientists to develop ´broadband´ sensors, which have a flat, undistorted input response for signals at frequencies ranging from 0.001 to 10 cycles per second (periods from 1/10 to 1000 seconds). Through simple digital filtering, broadband data can mimic both the former short- and long-period sensors.
Nuclear Testing and Nonproliferation
Return to:Table of Contents