Inproceedings,
Seismic calibration of the European Arctic
22nd Seismic Research Symposium --- Planning for verification of and compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), New Orleans, Louisiana, Defense Technical Information Center, (September 2000)
Abstract
The purpose of this two-year effort, which started on 1 January 1999,
is to support the construction of the U.S. Department of Energy (DOE)
Comprehensive Nuclear-Test-Ban Treaty Knowledge Base for detecting,
locating and identifying seismic events in the area of northern Fennoscandia,
the Kola Peninsula, Novaya Zemlya, and the surrounding waters of
the Barents and Kara Seas. The main objectives of the effort are
to assemble a set of historical seismic observations suitable for
characterizing all aspects of seismic wave propagation and seismic
sources in this region, to describe the principal seismic phases
observed in the seismograms, and to calibrate the region with respect
to seismic wave propagation (travel-times and amplitude-distance
relations). The main emphasis of work on this contract so far has
been on data collection. Waveform data have been complied for a range
of sources in the European Arctic: Nuclear tests at the Novaya Zemlya
test site, peaceful nuclear explosions conducted in the area, earthquakes
and presumed underwater explosions from 1970 to the present, and
representative blasts from mining operations in the Kola Peninsula,
northern Norway, Sweden, Finland and adjacent regions of European
Russia. Waveform data collected under this effort have been provided
in CSS 3.0 format, with the appropriate metadata included, to DOE
through the Lawrence Livermore National Laboratory, to the U.S. Department
of Defense through the Center for Monitoring Research, and to the
U.S. National Data Center. So far, segmented data for 111 events
have been extracted and copied to eight CD ROMs. In addition, a set
of seven Exabyte tapes has been produced, containing continuous data
in the form of 15-day segments around the origin times of three events
that occurred in the Noyaya Zemlya region during 1995-1997. Additional
data for events of special interest will be delivered during the
year 2000. The project is a collaborative effort between NORSAR and
the Kola Regional Seismological Centre (KRSC) of the Russian Academy
of Sciences. The main source of data for this project is the historical
waveform archives at NORSAR, containing data from the NORSAR teleseismic
array and the network of northern European smallaperture arrays.
These data have been supplemented with data provided by KRSC for
stations AMD and APA in northwestern Russia. The work under this
contract also includes analysis of the data compiled. So far, a study
of the P/S ratio as a regional discriminant in the European Arctic
has been conducted. Our conclusion from this study is that the P/S
ratio, even at high frequencies is, with present knowledge, not sufficiently
stable to be used as a reliable discriminant between earthquakes
and explosions. Future application of this discriminant will require
extensive regional calibration and detailed station-source corrections.
Work continues on other aspects of data analysis, such as a determination
of bounds on seismicity in the Kara Sea.
