Glossary

S-waves

A type of seismic wave that travels through the interior of the Earth. S-waves are secondary or shear waves in the ground that move perpendicular to the direction of the waves’ propagation.  S-waves can only move through solids as this kind of movement is impossible in liquid or gaseous materials. This property of S-waves provided the original evidence that the outer core of the Earth is liquid. Measuring the azimuths of S-waves and P-waves makes it possible to identify the direction from which the waves emanated. S-waves travel a fraction slower than P-waves. The distance of a source event can therefore be established by measuring the different arrival times of both waves.

Safeguards

Are a “set of activities by which the IAEA seeks to verify that a State is living up to its international undertakings not to use nuclear programmes for nuclear weapons purposes”. The safeguards system is based on assessment of the correctness and completeness of the State’s declarations to the IAEA concerning nuclear material
and nuclear-related activities. To date, 145 States have entered into such agreements with the IAEA, submitting nuclear materials, facilities and activities to the scrutiny of IAEA’s safeguards inspectors. 

SALT I & II

Same as Strategic Arms Limitation Talks

Sampling Rate

When converting an analog signal (ground motion) to a digital signal for recording and processing, the sampling rate is the number of samples of data taken per unit of time. For time-domain signals, it can be measured in hertz (Hz).

Seabed Treaty

Prohibits the placement of nuclear weapons, including the testing of them, or any other weapons of mass destruction on the seabed, the ocean floor, and in the subsoil of the ocean floor beyond a signatory's 12-miles coastal zone. The "Treaty on the Prohibition of the Emplacement of Nuclear Weapons and other Weapons of Mass Destruction on the Seabed and the Ocean Floor and in the Subsoil Thereof" opened for signature on February 11, 1971, and entered into force on May 18, 1972. As of March 2008, there were 93 parties to the treaty. 

Secure Signatory Accounts

The registration by a State Signatory with the CTBTO to obtain access to verification data and products.

Secure Signature Account

The registration by a State Signatory with the CTBTO to obtain access to verification data and products.

Security Council Resolution 1540 (2004)

Calls on all states to refrain from supporting, by any means, non-state actors which attempt to acquire, use or transfer nuclear, chemical or biological weapons and their delivery systems.  This UNSC resolution from April 2004 also calls for a committee to report on the progress of the resolution, asking states to submit a report on steps taken in conforming to the resolution.

Seismic

Related to movements of the ground that can be generated by earthquakes, explosions and a wide range of other events such as ocean waves, wind and human activities.

Seismic array

A type of seismic monitoring station. It employs several seismic sensors arranged in a certain geometric pattern across an area that can range from a few to several hundred square kilometres. A seismic array employs two types of seismic sensors, which measure both types of seismic waves: those that travel through the interior of the Earth (body waves) and waves that travel along its surface (surface waves). Seismic arrays help identify the location of an event based on information about the direction of a signal and its speed.

Seismic arrays

A type of seismic monitoring station. It employs several seismic sensors arranged in a certain geometric pattern across an area that can range from a few to several hundred square kilometres. A seismic array employs two types of seismic sensors, which measure both types of seismic waves: those that travel through the interior of the Earth (body waves) and waves that travel along its surface (surface waves). Seismic arrays help identify the location of an event based on information about the direction of a signal and its speed.

Seismic boreholes

Specially-drilled holes, often 50 meters deep or more, designed specifically for the placement of seismometers.

Seismic equipment

A seismic station has three basic parts: a seismometer to measure the ground motion, a recording system which records the data digitally with an accurate time stamp, and a communication system interface.

Seismic network

CTBTO’s seismic network consists of 50 primary stations and 120 auxiliary stations. The task of the network is to detect events that may be of a nuclear origin. The seismic technology can be used to distinguish between a natural and a man-made event, such as an earthquake and an explosion.

Seismic noise

Permanent background vibrations of the Earth’s surface that are considered disturbances when monitoring seismic signals.  Seismic noise is mostly generated by wind and ocean waves. Human activity, such as vehicle traffic and industrially-generated noise, can also create seismic noise. In order to eliminate the influence of seismic noise, seismic stations are built in remote areas as far away as possible from human activity.

Seismic vault

A small, secure building erected around seismometers that protect the seismometers and associated equipment from theft, weather, and wild animals.

Seismic vaults

Small, secure buildings erected around seismometers that protect the seismometers and associated equipment from theft, weather, and wild animals.

Seismic verification

Used to distinguish between a natural and a man-made event, such as various naturally occurring phenomena (e.g. volcanoes, earthquakes) and an underground nuclear test explosion.

Seismic waves

Describe movements of the ground that are generated by earthquakes, explosions and a wide range of other events such as ocean waves, wind and human activities. Seismic waves are essential for the detection of nuclear explosions. There are different types of seismic waves: body waves that travel through the interior of the Earth and surface waves that travel along its surface.  Both types of wave are measured in order to analyze the location, strength and nature of an event.

Seismology

The scientific study of earthquakes and the propagation of shockwaves through the Earth. Seismic waves can be caused also by nuclear explosions.

Seismometer

An instrument that converts ground motion into electric voltage.  Different types of seismometers are used at seismic stations.  The difference lies in the range of frequencies that are amplified by the seismometer.  Three-component stations have broadband sensors, measuring a wide range of frequencies to detect both body and surface waves. Seismic arrays have a combination of sensors, including vertical short period sensors for the detection of high-frequency body waves and broadband sensors for the detection of body waves and low-frequency surface waves.

Seismometer noise

Apparent ground motion (or self noise), registered by the sensor when isolated from any external source, due to the physical properties of the mechanical and electronic components of the sensor.

Seismometers

Instrument thats convert ground motion into electric voltage. Different types of seismometers are used at seismic stations. The difference lies in the range of frequencies that are amplified by the seismometer.  Three-component stations have broadband sensors, measuring a wide range of frequencies to detect both body and surface waves. Seismic arrays have a combination of sensors, including vertical short period sensors for the detection of high-frequency body waves and broadband sensors for the detection of body waves and low-frequency surface waves.

SEL

Standard Event List.  A bulletin listing events based on the processing of waveform data. The first Standard Event List, SEL1, includes seismic and hydroacoustic data. Based on SEL1, additional seismic data may be requested from auxiliary seismic stations. Results listed in SEL2 include the processing of additional seismic and infrasound data. The third list, SEL3, adds processing of data arriving late from auxiliary seismic and infrasound monitoring stations.

Self-noise

Extraneous non-acoustical signals, generated or induced in a measurement system. For example, with most all audio systems, if the volume is turned up very loud with no signal being played, one can hear a hissing sound when putting one’s ear close to the speaker in a very quiet room. See also System noise.

Short period

A passband of interest for studying seismic events, often for the study of body waves. Normally refers to higher frequencies above 1 Hz. See also Passband.

Sign

The signing of a treaty indicates that the country accepts the treaty and commits not to take any actions that would undermine its purposes until the country completes its ratification process (usually through its legislative or parliamentary body). This is according to the Vienna Convention on the Law of Treaties. A treaty is signed by a senior representative of a country (such as the president or secretary of state).

Signal

Significant information sought among a host of similar, but irrelevant, information available, such as background noise. Signals are often referred to as anomalies in the data.

Signals

Significant information sought among a host of similar, but irrelevant, information available, such as background noise. Signals are often referred to as anomalies in the data.

Signatory States

All countries that have signed the CTBT. The signing of a treaty indicates that the country accepts the treaty and commits not to take any actions that would undermine its purposes until the country completes its ratification process (usually through its legislative or parliamentary body). This is according to the Vienna Convention on the Law of Treaties. A treaty is signed by a senior representative of a country (such as the president or secretary of state).

Signature

The signing of a treaty indicates that the country accepts the treaty and commits not to take any actions that would undermine its purposes until the country completes its ratification process (usually through its legislative or parliamentary body). This is according to the Vienna Convention on the Law of Treaties. A treaty is signed by a senior representative of a country (such as the president or secretary of state).

Signed

The signing of a treaty indicates that the country accepts the treaty and commits not to take any actions that would undermine its purposes until the country completes its ratification process (usually through its legislative or parliamentary body). This is according to the Vienna Convention on the Law of Treaties. A treaty is signed by a senior representative of a country (such as the president or secretary of state).

Site survey

Detailed study of the proposed location of a CTBTO International Monitoring System station, covering all features of the site that may affect the operation of the station and the quality of the monitoring data provided by the station, such as accessibility, available infrastructure, technical support, meteorological factors, site security, background, and potential sources of anthropogenic factors that might affect the data.

Site surveys

Detailed study of the proposed location of a CTBTO International Monitoring System station, covering all features of the site that may affect the operation of the station and the quality of the monitoring data provided by the station, such as accessibility, available infrastructure, technical support, meteorological factors, site security, background, and potential sources of anthropogenic factors that might affect the data.

Skeptical

Examples of analysis skeptical of India's claim that its 1998 thermonuclear weapon test was successful:

Federation of American Scientists

New York Times

Nuclear Weapon Archive

Wisconsin Project on Nuclear Arms Control

SOFAR

Sound Fixing and Ranging Channel. This channel is typically at a depth of 600 to 1200 m. Sound waves are trapped there and move slower in this layer than in the layers below or above, making this channel a perfect tool for hydroacoustic monitoring.

South Pacific Nuclear-Weapon-Free-Zone

This treaty prohibits the testing, manufacturing, acquiring, and stationing of nuclear explosive devices in any member's territory. The treaty prohibits dumping radioactive wastes into the sea. In addition, the treaty requires all parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities. It was opened for signature on 6 August 1985, and entered into force on 11 December 1986. As of March 2008, there were 13 parties to the treaty: Australia, Cook Islands, Fiji, Kiribati, Nauru, New Zealand, Niue, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalul and Vanuatu. The treaty has three Protocols that refer to provisions of territories within the zone that belong to the United States, France, the United Kingdom, Russia, and China. All five nuclear weapon states have signed the protocols.

Southeast Asian Nuclear-Weapon-Free-Zone

The treaty prohibits the development, manufacture, acquisition or testing of nuclear weapons anywhere within the region of the ten full-member parties: Brunei Darussalam, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam. It also prohibits the transport of nuclear weapons through the region. Signatories also undertake to enact International Atomic Energy Agency safeguards and to refrain from dumping at sea, discharging into the atmosphere, or burying on land any radioactive material or waste. Opened for signature on 15 December 1995, the treaty entered into force on 27 March 1997. As of March 2008, all ten States Parties had ratified the treaty. However, none of the nuclear-weapon states (NWS) had yet signed the protocols.

Spent nuclear fuel

Fuel that has been removed from a nuclear reactor because it can no longer sustain power production for economic or other reasons.

SSEB

Standard Screened Event Bulletin. A bulletin containing all events that are considered potentially suspicious in the CTBT verification context.  The bulletin is the result of an automatic screening process where events are examined for their character. Natural events are discarded, while man-made events are included in the SSEB.

SSREB

Standard Screened Radionuclide Event Bulletin. A bulletin produced for those samples that contain one or more fission or activation products at abnormal concentrations. The SSREB is a dynamic product that incorporates information on all correlated events from any radionuclide station.

Standard Event List

A bulletin listing events based on the processing of waveform data. The first Standard Event List, SEL1, includes seismic and hydroacoustic data. Based on SEL1, additional seismic data may be requested from auxiliary seismic stations. Results listed in SEL2 include the processing of additional seismic and infrasound data. The third list, SEL3, adds processing of data arriving late from auxiliary seismic and infrasound monitoring stations.

Standard Event Lists

Bulletin listing events based on the processing of waveform data. The first Standard Event List, SEL1, includes seismic and hydroacoustic data. Based on SEL1, additional seismic data may be requested from auxiliary seismic stations. Results listed in SEL2 include the processing of additional seismic and infrasound data. The third list, SEL3, adds processing of data arriving late from auxiliary seismic and infrasound monitoring stations.

Standard Screened Event Bulletin (SSEB)

A bulletin containing all events that are considered potentially suspicious in the CTBT verification context.  The bulletin is the result of an automatic screening process where events are examined for their character. Natural events are discarded, while man-made events are included in the SSEB.

Standard Screened Radionuclide Event Bulletin (SSREB)

A bulletin produced for those samples that contain one or more fission or activation products at abnormal concentrations. The SSREB is a dynamic product that incorporates information on all correlated events from any radionuclide station.

State-of-health data

Provides information on the operational status of the station and quality of the raw monitoring data transmitted from the station. This is supplementary data provided by sensors connected to, or associated with, equipment and instrumentation at the station.

States Signatories

All countries that have signed the CTBT. The signing of a treaty indicates that the country accepts the treaty and commits not to take any actions that would undermine its purposes until the country completes its ratification process (usually through its legislative or parliamentary body). This is according to the Vienna Convention on the Law of Treaties. A treaty is signed by a senior representative of a country (such as the president or secretary of state).

Station

The equipment, facilities, infrastructure and staff required to carry out monitoring at a designated location within the CTBTO International Monitoring System.  A station includes all operational systems necessary for this function.  In addition, the station may include the equipment necessary to provide ancillary data, such as meteorological information and state-of-health sensors.

Station processing

The first phase of automatic processing, i.e. the independent analysis of waveform data from each single station.

Stations

The equipment, facilities, infrastructure and staff required to carry out monitoring at a designated location within the CTBTO International Monitoring System.  A station includes all operational systems necessary for this function.  In addition, the station may include the equipment necessary to provide ancillary data, such as meteorological information and state-of-health sensors.

Stockpile Stewardship Program

The US Department of Energy’s science-based programme which ensures the safety, security and reliability of the country’s nuclear weapons without nuclear testing. This programme has existed since 1992 when the US stopped nuclear testing and upheld a testing moratorium.  
Stockpile stewardship refers to the activities associated with research, design, development and testing of nuclear weapons and the assessment and certification of their safety and reliability. Stockpile management refers to the activities associated with production, maintenance, surveillance, refurbishment and dismantlement of the nuclear weapons stockpile.

Strategic Arms Limitation Talks

Between the Soviet Union and the United States between 1969 and 1979 were aimed at limiting missile systems and other strategic armaments. The first round of talks (SALT I) was held from 1969-1972, and the second from 1972-1979. SALT I concluded on 20 May 1971, when the ABM Treaty and the Interim Agreement limiting strategic offensive arms were signed. The SALT II Treaty was signed on 18 June 1979, but was not ratified by either country.

Strategic Arms Reduction Talks (START I & II)

Between the Soviet Union/Russian Federation and the United States were held from 1982 to 1993 to limit and reduce the numbers of strategic offensive nuclear weapons in each country's nuclear arsenal. The talks resulted in the 1991 START I Treaty, which entered into force in December 1994, and the 1993 START II Treaty. Each treaty is officially named the "Treaty between the United States of America and the Union of Soviet Socialist Republics on the Reduction and Limitation of Strategic Offensive Arms." START I was originally negotiated between and the Soviet Union and the United States and now applies to Belarus, Kazakhstan, the Russian Federation, Ukraine and the United States. Belarus, Kazakhstan, and Ukraine have all renounced their possession of nuclear weapons under the 1992 Lisbon Protocol to START I. START II, which calls for further reductions in Russia and the United States has been ratified by the two countries, but has not yet entered into force.

Strategic nuclear warheads

Warheads placed on long-range delivery systems, on land-based Intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and long-range bombers.

Sub-critical tests

Non-nuclear tests that are used to gather information about nuclear warhead design and performance. Although sub-critical tests use some fissile materials, the tests do not produce a nuclear explosion or lead to any release of radioactivity. It is not considered a nuclear text explosion.

Supreme national interest

Essential requirements that influence and guide a state in the creation of its foreign policy. Supreme national interests include territorial integrity, self preservation, independence, military security, and economic well-being.

Surface forcings

Surface forcings have to do with the reduction in velocity near the surface as a function of surface roughness. Therefore, wind velocity profiles are quite different for different terrain types. Due to low surface roughness on the relatively smooth water surfaces, wind speeds do not increase as much with height above sea level as they do on land. Over a city or rough terrain, the wind gradient effect could cause a reduction of 40% to 50% in wind speeds, while over open water or ice, the reduction may be only 20% to 30%. See atmospheric boundary layer.

Surface waves

Seismic waves that travel along the surface of the Earth.  Surface waves result from the interference between the two types of body waves. They are slower than body waves and can be very destructive.  Surface waves are measured in order to obtain information on the depth and strength of an event.

System noise

Self noise of the acquisition system, excluding the seismometer. See also Self-noise.

System Performance

The timeliness, quality and quantity of data harvested by the 337 monitoring facilities of the International Monitoring System, which are produced, transmitted, processed and distributed to Member States.

System sustainment

The enhancement, improvement, refinement and replacement of current equipment with newly evolved technologies.