March, 2001
Q: How can scientists detect and measure explosions without getting too close for comfort?
A: By using the seismic waves produced by these explosions!
While seismic waves are generally associated with tectonic earthquakes, they can be produced by a variety of energy-releasing phenomena: volcanic eruptions and explosions, to name just two. Each of these produces different types of "signature" waveforms, so scientists can use records from many seismograph stations to pinpoint the location and source of the energy release. This month, we take a look at an uncommon application of these techniques: how seismology helped determine the circumstances surrounding the sinking of the Russian submarine, the Kursk, in August 2000.
Indeed, its explosion-monitoring capabilities are one of the major reasons many countries are interested in seismology. Since seismic waves travel through the Earth and know no political boundaries, seismologists play a role in monitoring the Comprehensive [Nuclear] Test Ban Treaty (CTBT) by using their recording stations to "listen" for explosions around the world. Seismologists also help "keep the peace" by informing governments when seismic waves were, in fact, just caused by earthquakes.
Related Web Sites
Death of the Kursk: A CNN "in-depth special" on the sinking of the Kursk, this site includes a wide range of news reports, photographs, and video footage of the submarine, rescue attempts, and social and political implications of the disaster.
Russian Submarine Kursk Catastrophe: Posted by the Russian Naval Museum, this page contains specifics about the submarine as well as several dissenting views of the circumstances surrounding its sinking (last updated November 2000, prior to the publication of the featured paper).
Forensic Seismology Supports Comprehensive Test Ban Treaty: This article, written by Dr. John Zucca at Lawrence Livermore National Laboratory, talks about the challenges posed by the need to monitor and analyze ground motions around the globe. He also presents a short history of CTBT monitoring efforts and information on regional studies.
Frequently Asked Questions about Nuclear Explosions and Seismology: This page from the Berkeley Seismological Laboratory has brief answers to some common questions, as well as links to other sources of information.
Related Classroom Activities and Resources
Waves, Seismograms, and Seismometers: These illustrated notes, prepared by Professor Charles Ammon at St. Louis University, provide basic background information on how seismic waves are produced, how they travel, and how they are recorded.
Virtual Earthquake: Created by Cal State University - Los Angeles with funding from the NSF, this "Geology Lab Online" allows students to use seismograms to locate of an earthquake and provides immediate feedback. It may be helpful to look at the IRIS "one-pager" (see below) or to provide copies for students as an overview of the exercise.
How Are Earthquakes Located?: This one-page fact sheet from IRIS's Education and Outreach Department provides a concise explanation of how seismograms are used to find the location, size, and origin time of an earthquake (or other event).
Earthquake!: A set of activities developed at UC Berkeley, these exercises are designed for middle school and high school students. There are teacher plans for the exercises, which include "Can You Read a Quake?", "Race of the Waves", and "Where Did It Hit?". These activities can be printed for use without computer access.
Earthquake Magnitudes: The Princeton Earth Physics Project has produced this set of seismology-related activities for high school students. They reinforce concepts such as powers of ten (orders of magnitude), magnitude and energy release, and wave propagation, and ask students to compare the size and energy of an earthquake with that of an explosion.
Science News Write-Up: Write a report on this article for your class! Here is a suggested outline to help you organize the report.
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