Development of calibration techniques for the Comprehensive Nuclear-Test-Ban
Treaty (CTBT) international monitoring system
Physics of the Earth and Planetary Interiors, 113 (1-4):
11--24 (June 1999)DOI: 10.1016/S0031-9201(99)00033-3
Abstract
A prototype International Data Centre (pIDC) is developing and testing
concepts for the International Monitoring System that will be put
into place to monitor compliance with the recently-signed Comprehensive
Test Ban Treaty (CTBT). The testing includes the routine production
of a daily bulletin of global seismic activity, several days after
real time, since the beginning of 1995. A wider variety of seismic
phases are used for location than is the practice of existing agencies
producing global bulletins at greater delays, and another difference
is that observed slowness vectors are used in addition to arrival
time. Comparisons of pIDC bulletins with those provided by national
agencies that operate denser networks have demonstrated both random
and systematic errors in location that often exceed the formal error
estimates. The pIDC is developing and testing techniques to reduce
systematic biases through region- and path-dependent corrections
to travel-time and slowness, and to better account for random errors.
Initial results from this very long-term project are encouraging.