Forensic seismology

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Forensic seismology is the forensic use of the techniques of seismology to detect and study distant phenomena, particularly explosions, including those of nuclear weapons. [1]

Because of the efficiency with which seismic waves propagate through the Earth and the technical difficulties of decoupling explosions to diminish their seismic radiation, forensic seismology is a critical technique in the enforcement of bans on underground nuclear testing. [2]

In addition to nuclear explosions, the signatures of many other kinds of explosions [3] can also be detected and analyzed by forensic seismology, [1] and even other phenomena such as ocean waves (the global microseism), the movement of icebergs across the sea floor or in collision with other icebergs, [4] or explosions within submarines. [5] [6]

Organizations with expertise in forensic seismology include AWE Blacknest, Los Alamos National Laboratory, Sandia National Laboratory, and Lawrence Livermore National Laboratory.

Seismic detection of nuclear detonations

Forensic Seismology is one of several other methods used by the global community to determine compliance with the Comprehensive Nuclear Test-Ban Treaty (CTBT). A network of approximately 170 seismic stations, along with data generated from sources such as infrasound, hydroacoustics, and radionuclide detection, is used to identify and locate nuclear detonations. [7] Forensic seismology is specifically used to locate nuclear detonations that may have occurred underneath the ground.

Seismic stations record underground pressure waves and transmit this data for processing via secure communication links. There are many challenges involved with trying to differentiate a nuclear explosion from other natural and man-made phenomena, such as earthquakes, mining explosions, and construction. [7] Nuclear explosions exceeding 150 kilotons generate pressure waves that primarily travel through the Earth's core and mantle. [7] These types of explosions are straightforward to identify because the mixture of rock the signals pass through is fairly homogeneous and the signals generated are free from noise. Smaller nuclear explosions are more difficult to identify because pressure waves primarily travel through the Earth's upper mantle and crust, leading to signal distortion due to the heterogeneity of rocks at this depth. [7]

Nations may also conduct clandestine underground tests that are not easily identifiable. One method of hiding an underground nuclear detonation is called decoupling. This involves detonating a nuclear warhead in an underground cavity in order to significantly muffle the amplitude of the subsequent underground pressure waves. [7] Another proposed method of hiding nuclear detonations is called mine masking. This technique uses a larger explosion to mask a smaller nuclear explosion. [8] The feasibility of mine masking has been called into question because seismic events large enough to mask a nuclear explosion are exceedingly rare and would draw suspicion. [8] Smaller nuclear detonation yields may also be hard to detect because they produce readings similar to small earthquakes or other natural events. [8]

When seismic data is gathered, it has to be processed to produce meaningful information. Algorithms are used to isolate patterns, remove noise, and generate estimates. The development of efficient algorithms for nuclear detonation detection has led to many advancements in other fields such as kriging, an advanced method of interpolation used primarily in geostatistics. [7] Algorithms are used to identify key characteristics of wave forms, such as peak-to-peak distance, amplitude, phase, P wave amplitude, and S wave amplitude. P waves, or primary waves, are compression waves that propagate quickly through rock, and are generally the first waves to reach seismic stations. [7] S waves, or shear waves, arrive after P waves. The ratio of P to S waves is one of several important values used to characterize seismic events. When a nuclear detonation has been identified, algorithms are used to estimate the detonation time, explosive yield and depth of burial. [9] [10]

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<span class="mw-page-title-main">Comprehensive Nuclear-Test-Ban Treaty</span> 1996 treaty banning all nuclear weapons testing

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nations General Assembly on 10 September 1996, but has not entered into force, as eight specific nations have not ratified the treaty.

<span class="mw-page-title-main">Seismology</span> Scientific study of earthquakes and propagation of elastic waves through a planet

Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic microseism, atmospheric, and artificial processes such as explosions and human activities. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time, created by a seismograph is called a seismogram. A seismologist is a scientist works in basic or applied seismology.

<span class="mw-page-title-main">Nuclear bunker buster</span> Earth-penetrating nuclear weapon

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<span class="mw-page-title-main">Nuclear weapons testing</span> Controlled detonation of nuclear weapons for scientific or political purposes

Nuclear weapons tests are experiments carried out to determine the performance, yield, and effects of nuclear weapons. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by different conditions, and how personnel, structures, and equipment are affected when subjected to nuclear explosions. However, nuclear testing has often been used as an indicator of scientific and military strength. Many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status through a nuclear test.

A hypocenter or hypocentre, also called ground zero or surface zero, is the point on the Earth's surface directly below a nuclear explosion, meteor air burst, or other mid-air explosion. In seismology, the hypocenter of an earthquake is its point of origin below ground; a synonym is the focus of an earthquake.

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Peaceful nuclear explosions (PNEs) are nuclear explosions conducted for non-military purposes. Proposed uses include excavation for the building of canals and harbours, electrical generation, the use of nuclear explosions to drive spacecraft, and as a form of wide-area fracking. PNEs were an area of some research from the late 1950s into the 1980s, primarily in the United States and Soviet Union.

The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is an international organization that will be established upon the entry into force of the Comprehensive Nuclear-Test-Ban Treaty, a Convention that outlaws nuclear test explosions. Its seat will be in Vienna, Austria. The organization will be tasked with verifying the ban on nuclear tests and will operate therefore a worldwide monitoring system and may conduct on-site inspections. The Preparatory Commission for the CTBTO, and its Provisional Technical Secretariat, were established in 1997 and are headquartered in Vienna, Austria.

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Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary based on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.

<span class="mw-page-title-main">Underwater explosion</span> Chemical or nuclear explosion that occurs underwater

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<span class="mw-page-title-main">Underground nuclear weapons testing</span> Test detonation of nuclear weapons underground

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National technical means of verification (NTM) are monitoring techniques, such as satellite photography, used to verify adherence to international treaties. The phrase first appeared, but was not detailed, in the Strategic Arms Limitation Treaty (SALT) between the US and USSR. At first, the phrase reflected a concern that the "Soviet Union could be particularly disturbed by public recognition of this capability [satellite photography]...which it has veiled.". In modern usage, the term covers a variety of monitoring technologies, including others used at the time of SALT I.

In seismology, a microseism is defined as a faint earth tremor caused by natural phenomena. Sometimes referred to as a "hum", it should not be confused with the anomalous acoustic phenomenon of the same name. The term is most commonly used to refer to the dominant background seismic and electromagnetic noise signals on Earth, which are caused by water waves in the oceans and lakes. Characteristics of microseism are discussed by Bhatt. Because the ocean wave oscillations are statistically homogenous over several hours, the microseism signal is a long-continuing oscillation of the ground. The most energetic seismic waves that make up the microseismic field are Rayleigh waves, but Love waves can make up a significant fraction of the wave field, and body waves are also easily detected with arrays. Because the conversion from the ocean waves to the seismic waves is very weak, the amplitude of ground motions associated to microseisms does not generally exceed 10 micrometers.

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The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, or CTBTO Preparatory Commission, is an international organization based in Vienna, Austria, that is tasked with building up the verification regime of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). The organization was established by the States Signatories to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in 1996.

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The World-Wide Standardized Seismograph Network (WWSSN) – originally the World-Wide Network of Seismograph Stations (WWNSS) – was a global network of about 120 seismograph stations built in the 1960s that generated an unprecedented collection of high quality seismic data. This data enabled seismology to become a quantitative science, elucidated the focal mechanisms of earthquakes and the structure of the Earth's crust, and contributed to the development of plate tectonic theory. The WWSSN is credited with spurring a renaissance in seismological research.

<span class="mw-page-title-main">Ground motion</span>

Ground motion is the movement of the Earth’s surface from earthquakes or explosions. Ground motion is produced by seismic waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the Earth and along its surface. This can be due to natural events, such as earthquakes and volcanic eruptions, or human activities, such as the detonation of nuclear weapons. There are two main types of seismic waves: body waves and surface waves. Body waves travel through the interior of the Earth, while surface waves travel along the Earth's surface. Ground motion is typically caused by surface waves, which are the most destructive type of seismic waves.

References

  1. 1 2 J. David Rogers and Keith D. Koper. "Some Practical Applications of Forensic Seismology" (PDF). Retrieved 2011-09-09.
  2. ↑ John J. Zucca (September 1998). "Forensic Seismology Supports CTBT". Lawrence Livermore National Laboratory. Archived from the original on 2013-11-03. Retrieved 2011-09-09.
  3. ↑ Koper, K. D., T. C. Wallace, and R. C. Aster (2003), Seismic recordings of the Carlsbad, New Mexico, pipeline explosion of 19 August 2000, Bulletin of the Seismological Society of America, 93(4), 1427–1432
  4. ↑ Martin, S., R. Drucker, R. Aster, F. Davey, E. Okal, T. Scambos, and D. MacAyeal (2010), Kinematic and seismic analysis of giant tabular iceberg breakup at Cape Adare, Antarctica, Journal of Geophysical Research-Solid Earth, 115, doi:10.1029/2009JB006700
  5. ↑ Richard A. Lovett (5 March 2009). "Forensic seismology". COSMOS magazine. Archived from the original on 9 March 2011. Retrieved 9 September 2011.
  6. ↑ Christina Reed (February 2001). "Sinking the Kursk". GeoTimes. Retrieved 2011-09-09.
  7. 1 2 3 4 5 6 7 "Forensic Seismology Supports CTBT". str.llnl.gov. Archived from the original on 2013-11-03. Retrieved 2017-04-23.
  8. 1 2 3 APPENDIX E Dealing with Evasive Underground Nuclear Testing | The Comprehensive Nuclear Test Ban Treaty: Technical Issues for the United States | The National Academies Press. 2012. doi:10.17226/12849. hdl:2027/mdp.39015041921126. ISBN   978-0-309-14998-3.
  9. ↑ Douglas, Alan (2017). Forensic Seismology and Nuclear Test Bans. Cambridge University Press. ISBN   9781107033948.
  10. ↑ Dahlman, Ola and Hans Israelson. Monitoring Underground Nuclear Explosions. New York: Elsevier, 1977,440pp.
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