The May 1998 India and Pakistan Nuclear Tests

This page replaces the earlier pages posted here which provided information about the Indian and Pakistan nuclear tests in May, 1998. If you would like to read a summary of a seismological analysis of the test please follow this link: The May 1998 India and Pakistan Nuclear Test, by Terry C. Wallace, which will appear in the September issue of the Seismological Research Letters.


General Information

On May 11, 1998 the Indian government announced that they had conducted a series of successful nuclear tests at their test facility in the Rajasthan Desert. On May 13, the Indian government announced that it conducted two further tests. The Pakistan government responded with a series of there own tests. On May 28 the Pakistanis announced that they had exploded 5 nuclear devices in the southwestern part of Pakistan. These tests were followed by another test on May 30. The regional map below

shows the location of the various tests.


Seismic Data

Seismic data is available from the IRIS DMC, which collected all the "open" seismic data in near realtime. Some of the world wide recordings for the Indian explosion on May 11 from the IRIS GSN are displayed here. Some of the IRIS GSN recording for the May 28 Pakistan test are displayed here. If you are a European viewer of this page the data is more easily accessed through ORFEUS.

The explosions were also recorded by the pIDC, which is a prototype monitoring system for a Comprehensive Test Ban Treaty (CTBT). The pIDC automatically detected and located the largest of the tests. Some of the PIDC stations are within the US, including a shortperiod array in Alaska (ILAR). Even thought ILAR is 83 degrees (more than 8500 km) from the Pakistan test site, it still produced a nice shortperiod seismic record for the May 28 test.

The tests were well recorded by KNET , an array of broadband seismic stations located in Kyrgyzstan, and operated by Frank Vernon (IGPP, UCSD). The Institute for Geosciences and Natural Resources (Hannover, Germany) in Germany operate the German Experimental Seismic System (GERESS), a small aperture array. The GERESS data provides an excellent constraint on the size of the Indian explosion.
Comparison of Events

The May 11 explosion was the largest (mb = 5.2), followed by the May 28 (mb = 4.8) and May 30 (mb = 4.6) events. Shown below is a comparison of the May 11 and May 28 events. It is obvious that the Pakistan event

has a far more complex waveform. This has lead to speculation that the of seconds. However, a comparison between May 28 and May 30 exlosions casts doubt on this interpretation.

Related Topics

Seismic Discrimination
One of the principle problems for seismology in nuclear monitoring is the discrimination of man made seismic events from natural earthquakes.
Seismic Yield Estimates
There are several ways to calculate the explosive yield from nuclear explosions from seismic signals. There are two main factors effecting the yield/seismology relationships: emplacement conditions (coupling) and seismic attenuation, especially in the upper mantle.


Other information about the Pakistan nuclear weapons program:

A status review of Pakistan's program

by Andrew Koch and Jennifer Topping including a map of facilities.


A review of Pakistan's nuclear weapons and weapon delivery systems
by Ted Flaherty of the Center for Defense information.


Other information about the Indian nuclear weapons program:

satellite images of the India test site.

Vipin Gupta and Frank Pabian (Sandia Lab)

This page is maintained and updated by the SASO group at the University of Arizona. It is not an offical government document, and links to other pages are provided for information only. Contact is Terry Wallace at