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.