Hein Haak

Comparing Waveforms by Digitization and Simulation of Waveforms for Four Parkfield Earthquakes Observed in Station dbn, The Netherlands

Waveforms from the 2004 Parkfield earthquake are compared with three earlier events in 1922, 1934, and 1966, all recorded in station dbn, The Netherlands, at 80° epicentral distance. Digitization of analog records and simulation of digital data enabled the correlation of surface waves for all events. Normalized correlation values are greater than 0.8 for the Parkfield events themselves, compared to values less than 0.5 for correlation with other events in the same region, either with a different mechanism at close distances (1983 Coalinga and 2003 San Simeon) or with the same mechanism, but at larger distances along the same fault system (1984 Morgan Hill). We find that waveforms from sources with the same mechanism show the highest correlations. Waveform amplitudes of the Parkfield events are similar within the accuracy of the calibration of the instrumentation.

Establishing the Verification Regime

The CTBT verification regime is designed to provide confidence that nuclear explosions can be detected and identified as such anywhere and at any time. The monitoring component of this regime therefore needs to be global in its coverage and on the alert at all times to pick up signs of possible non-compliance with the Treaty. The system, now nearing its completion, is the most comprehensive technical system ever established to verify compliance with a treaty in the multilateral arena, and at the same time among the more ambitious undertakings ever to monitor all environments of the earth. The monitoring component of the regime is illustrated schematically in Fig. 6.1, which shows sensors of the International Monitoring System (IMS) providing data via the Global Communications Infrastructure to the International Data Center (IDC) of the Provisional Technical Secretariat (PTS) of the CTBTO Preparatory Commission, which in turn provides analysis results and, if requested, also raw data to National Authorities for their use.

To Test or Not to Test

On July 16, 1945 the world changed and on August 6 the world knew. The “Trinity” nuclear test in the Alamogordo desert in New Mexico, USA marked the beginning of the military nuclear era. The destruction of the Japanese cities of Hiroshima on August 6 and of Nagasaki on August 9, 1945 demonstrated the overwhelming power of this new weapon. These explosions marked the end of the Second World War and the beginning of a nuclear arms race: an arms race that divided the world between those having nuclear weapons and those that decided not to have them or that so far have been unable to acquire them. Eight States have conducted in all more than 2000 nuclear test explosions involving some 2400 nuclear devices. The USA and the former Soviet Union have carried out the lion’s share of these tests.

Synergy with Science

This chapter reviews the long-standing relationship between science and the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and how this relationship has, on the one hand, helped develop individual sciences and, on the other hand, significantly improved the CTBT verification system and the ability of countries to verify compliance with the treaty. It also discusses how data produced by the International Monitoring System (IMS) can be used for other purposes, in particular, applications related to key global issues such as global warming and environmental protection. Such dual use provides additional benefits to states from their large investments in the IMS and strengthens relations between the Provisional Technical Secretariat/Technical Secretariat (PTS/TS) of the CTBT Organization (CTBTO) and the scientific community. This relationship is important to maintaining the PTS/TS as a viable entity, able to recruit competent staff. Cooperation with the scientific community is also essential to keeping the development of the techniques and procedures used at the PTS/TS in pace with scientific and technological developments, within the constraints set by the CTBT.

On-Site Inspections

The on-site inspection (OSI) regime is the ultimate verification measure of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), comprising strong political, technical, and operational elements. It adds to the deterrence against clandestine tests and is an important measure to determine compliance. A state can request an OSI of an event of concern either following a process of consultation and clarification or without going through such a process. Either way, time is of the essence in the decisionmaking and conduct of an OSI. While some effects from a nuclear explosion may be long lasting, others can be short lived and thus time sensitive. This requires that an OSI inspection team and its equipment can be deployed and initiate inspection activities in a timely manner within the six-day time frame specified in the CTBT.

Monitoring Nuclear Explosions in the Oceans

The United States and the former Soviet Union are the only two countries that have carried out underwater nuclear explosions. They have conducted five explosions each: the United States at test sites in the Pacific Ocean and the former Soviet Union in the Arctic Ocean, close to Novaya Zemlya. The first underwater nuclear explosion, named Baker, was a test in shallow water conducted as early as 1 July 1946 at the Bikini atoll to study the effects of such nuclear explosions on naval ships, as seen in Figure 4.1.

Verifying the CTBT—A State Perspective

How can countries verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and detect and deter violations? The key conclusions in this book hinge on the fact that verification of compliance and non-compliance with the CTBT rests with the states parties. Verification is essentially a political process based on a broad range of verification tools that have improved over the last decade. The CTBT identifies three steps in the verification procedure: monitoring for evidence of clandestine tests, engaging in a consultation and clarification process to resolve issues of concern, and requesting and conducting on-site inspections (OSIs) to clarify whether a nuclear explosion has been conducted in violation of the treaty and to gather facts that might help to identify the possible violator. Should a clandestine activity be identified, the actions to be taken will be addressed on a case-by-case basis.

Setting the Political Stage

Calls for the cessation of nuclear testing can be traced back to the beginning of the nuclear age. Over the years a number of attempts to negotiate an end to testing failed, usually because of an inability to agree on verification provisions, in particular on-site inspections. However, in 1963, the United States, United Kingdom, and Soviet Union negotiated the Treaty Banning Nuclear Weapon Tests in the Atmosphere, Outer Space and Under Water, known as the Partial Test Ban Treaty (PTBT), a precursor to the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Because underground testing was excluded from the ban, onsite inspections were not called for. However, the PTBT did include in its Preamble and Article I a commitment to negotiate “the permanent banning of all nuclear test explosions” (PTBT 1963). In 1974 the United States and the Soviet Union signed the Threshold Test Ban Treaty (TTBT), which prohibited tests having a yield exceeding a threshold of 150 kilotons (equivalent to 150,000 tons of TNT). Although the treaty did not enter into force until the two countries completed a verification protocol in 1990, both parties to the TTBT also undertook an obligation in the Preamble and Article I to continue negotiations toward the cessation of all underground nuclear weapon tests (TTBT 1974/1990).

Monitoring Atmospheric Nuclear Explosions

A little more than 30 years ago, in October 1980, China conducted its last nuclear test explosion in the atmosphere. This marked the end of atmospheric testing by all countries. The United Kingdom, United States, and Soviet Union, as depositories, had already signed the Partial Test Ban Treaty (PTBT) in 1963, which banned explosions in the atmosphere, in space, and under water. France, the fourth country that conducted atmospheric tests, ended its testing in the atmosphere in 1974. A total of 517 nuclear explosions were carried out in the atmosphere: United Kingdom 21, China 22, France 50, United States 210, and Soviet Union 214. As noted in Chapter 1, the PTBT contains no verification provisions. There might be several reasons for that: explosions in the atmosphere are generally easy to detect, and national monitoring equipment, such as for atmospheric radionuclide surveillance, was already available and operational at the time the treaty was signed. The United States launched its satellite-based Vela project in 1963 to monitor atmospheric nuclear explosions, as discussed under national technical means (NTM) below. The three depositories of the PTBT were also ready to move testing underground to reduce radioactive fall-out and thereby also the information that other states might obtain from analyzing the fall-out.

The CTBTO Preparatory Commission and the World

The CTBTO Preparatory Commission has close relations with many global actors. States Signatories are the organization’s masters, providing the funds needed as well as getting back investments in the monitoring stations they host. States provide personnel to the PTS, which has an extensive program for training national experts. States are also the customers for the data and products produced by the PTS during the testing and provisional operation of the emerging global monitoring network.