Comprehensive (nuclear) Test Ban Treaty Research
Seismic moment tensors hold potential for event discrimination. At issue is
the use of regional to far regional distance methodologies with sparse
network geometries as will be the case for the monitoring of low yield
explosions using the International Monitoring System (IMS). Dreger and
Woods (
1998 preprint here!) have demonstrated that the anomalous
radiation of Nevada Test Site (NTS) nuclear explosions may be discerned using
as few as two regional distance broadband stations. Nuclear explosions are
often accompanied by "tectonic release", possibly triggered earthquakes or
other secondary source processes. It is the presence of tectonic release that
poses the greatest challenge in the quest to discriminate an explosion from
and earthquake using long-period waves and a regional distance seismic
moment tensor methodology.
If seismic moment tensors do in fact provide discrimination capability
the automated application of the methodology to the low frequency
wavefield data stream may be tried. The Berkeley Seismological Laboratory
has recently completed the first phase in the development, implementation
and application of
automated seismic moment tensor codes at the
Prototype International Data Center (PIDC).
Event location is of critical importance in the monitoring of the CTBT.
The objectives of CTBT monitoring using the IMS involve the location of
events to magnitude 4.0 on a global scale with absolute mislocation error
of less than 18 km. This is a tall order. We have investigated regional
and far-regional event location using sparse networks of broadband
stations in a controlled experiment in which southern California
earthquakes are taken as ground truth and locations using regional
broadband stations are compared. This research is also to improve the
Berkeley Seismological Laboratories own capability of earthquake monitoring
in central and northern California.
Follow this link to see a paper describing
our location study.