On September 24, 1996, President Clinton signed the Comprehensive Nuclear Test Ban Treaty at the United Nations Headquarters. Over the next five months, 141 nations, including the four other nuclear weapon statesâ€"Russia, China, France, and the United Kingdomâ€"added their signatures to this total ban on nuclear explosions. To help achieve verification of compliance with its provisions, the treaty specifies an extensive International Monitoring System of seismic, hydroacoustic, infrasonic, and radionuclide sensors. This volume identifies specific research activities that will be needed if the United States is to effectively monitor compliance with the treaty provisions.

Pure appl. geophys., by 161 nations. Entry of the treaty into force, however, is still uncertain since it requires ratification by all 44 nations that have some nuclear capability and, as of 15 June 2001, only 31 of those nations have done so. Although entry of the CTBT into force is still uncertain, seismologists and scientists in related fields, such as radionuclides, have proceeded with new research on issues relevant to monitoring compliance with it. Results of much of that research may be used by the International Monitoring System, headquartered in Vienna, and by several national centers and individual institutions, to monitor compliance with the CTBT. New issues associated with CTBT monitoring in the 21st century have presented scientists with many new challenges. They must be able to effectively monitor com pliance by several countries that have not previously been nuclear powers. Effective monitoring requires that we be able to detect and locate much smaller nuclear events than ever before and to distinguish them from small earthquakes and other types of explosions. We must have those capabilities in regions that are seismically active and geologically complex, and where seismic waves might not propagate efficiently.

In September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data centre (IDC), and on-site inspections, to verify compliance. This volume contains research papers focusing on seismic ecent location in the CTBT context. The on-site inspection protocol of the treaty specifies a search area not to exceed 1000 square km. Much of the current research effort is therefore directed towards refining the accuracy of event location by including allowances for three-dimensional structure within the Earth. The aim is that the true location of each event will lie within the specified source zone regarding postulated location. The papers in this volume cover many aspects of seismic event location, including the development of algorithms suitable for use with three-dimensional models, allowances for regional structure, use of calibration events and source-specific station corrections. They provide a broad overview of the current international effort to improve seismic event location accuracy, and the editors hope that it will stimulate increased interest and further advances in this important field.

On September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data center (IDC), and on-site inspections to verify compliance. Seismic methods play the lead role in monitoring the CTBT. This volume concentrates on the measurement and use of surface waves in monitoring the CTBT. Surface waves have three principal applications in CTBT monitoring: to help discriminate nuclear explosions from other sources of seismic energy, to provide mathematical characterizations of the seismic energy that emanates from seismic sources, and to be used as data in inversion for the seismic velocity structure of the crust and uppermost mantle for locating small seismic events regionally. The papers in this volume fall into two general categories: the development and/or application of methods to summarize information in surface waves, and the use of these summaries to advance the art of surface-wave identification, measurement, and source characterization. These papers cut across essentially all of the major applications of surface waves to monitoring the CTBT. This volume therefore provides a general introduction to the state of research in this area and should be useful as a guide for further exploration.

In September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data centre (IDC), and on-site inspections, to verify compliance. This volume contains research papers focusing on seismic ecent location in the CTBT context. The on-site inspection protocol of the treaty specifies a search area not to exceed 1000 square km. Much of the current research effort is therefore directed towards refining the accuracy of event location by including allowances for three-dimensional structure within the Earth. The aim is that the true location of each event will lie within the specified source zone regarding postulated location. The papers in this volume cover many aspects of seismic event location, including the development of algorithms suitable for use with three-dimensional models, allowances for regional structure, use of calibration events and source-specific station corrections. They provide a broad overview of the current international effort to improve seismic event location accuracy, and the editors hope that it will stimulate increased interest and further advances in this important field.

In September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data center, and onsite inspections, to verify compliance. The problem of identifying small-magnitude banned nuclear tests and discriminating between such tests and the background of earthquakes and mining-related seismic events, is a challenging research problem. Because they emphasize CTBT verification research, the 12 papers in this special volume primarily addresses regional data recorded by a variety of arrays, broadband stations, and temporarily deployed stations. Nuclear explosions, earthquakes, mining-related explosions, mine collapses, single-charge and ripple-fired chemical explosions from Europe, Asia, North Africa, and North America are all studied. While the primary emphasis is on short-period, body-wave discriminants and associated source and path corrections, research that focuses on long-period data recorded at regional and teleseismic distances is also presented Hence, these papers demonstrate how event identification research in support of CTBT monitoring has expanded in recent years to include a wide variety of event types, data types, geographic regions and statistical techniques.

In September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data centre (IDC), and on-site inspections, to verify compliance. A global hydroacoustic monitoring system is being planned and implemented for verification of the CTBT. Much of the research conducted over the past several decades on acoustic surveillance of the oceans, formerly driven by the need to detect and track submarines, is now being applied to the development of effective monitoring methods to verify compliance with the CTBT. The aim of this volume on Hydroacoustic Monitoring of the CTBT is to summarize the research being conducted in this field and to provide basic references for future research. Much of the new research emphasizes major advances in understanding the coupling of ocean acoustic waves with elastic waves in the solid Earth. Topics covered include source excitation, detection and classification of events generating hydroacoustic signals, discrimination between underwater explosions and naturally occurring events, as well as topics in coupling of acoustic to seismic wavefields.