FOIA: High Frequency 3-Component Waveform Inversion for Source and Structural Parameters

WAVEFORM_INVERSION.pdf
High Frequency 3-Component Waveform Inversion for Source and Structural Parameters
Report presents the results of 3 studies dedicated to the seismic source characterization. Goal is to develop techniques for classification of weak seismic events; earthquakes, quarry blasts, mine collapses and underground nuclear explosions.
Document date: 1998-09-01
Department: Dept. of Physics, University of Colorado
Author: Danny J. Harvey, Anatoil L. Levshin
Document type: report
pages: 57


Archivist's Notes: Good quality document. Contains a report documentation page. Unlimited distribution. Original report was 54 pages. No handwritten marks or blackouts.

Summary

1. The overall purpose of the study described in the document was to discriminate between natural and manmade seismic events in an effort to effectively enforce a nuclear test ban treaty;

2. The document was not written for laymen, but would be of interest to anyone studying seismology and/or nuclear physics;

3. The document contains a number of interesting diagrams;

4. The data obtained was from seismometer networks installed at mining facilities in Kazakhstan and Russia, and at a former nuclear test site in China. In the case of China, the document includes data for three specific events at or near the Lop Nor test facility - an earthquake and two nuclear explosions;

5. The authors verified that a particular seismic event, the collapse of a salt mine in the Urals on January 5, 1995, was probably natural in origin;

6. The authors confirmed that an explosion in the area of an existing fault will likely trigger a seismic event, and that a shallow seismic event in a low-seismicity area can indicate a "suspicious event";

7. The authors discerned distinct differences in data sets according to the type of event recorded and concluded that such data can definitively identify a seismic event as a mining blast, mine collapse, nuclear explosion, or natural or manmade tectonic event.

[edit on 11/25/2007 by PrplHrt]

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Abstract: We present the results of three studies to develop and verify techniques to classify weak seismic events. (1) The method and results of full waveform inversion for both detailed source parameters and structure parameters are described. Input data were seismograms from industrial explosions in Eastern Kazakhstan recorded by the NRDC seismic network in 1987. Very good fits were produced between the synthetic seismograms and the observed data on all three components simultaneously and for P-wave, Rayleigh wave, and Love wave. We interpreted some of the inverted source parameters as characteristic of several different types of industrial surface mining operations. (2) The same technique was used to determine detailed source and structure parameters using an event that is highly relevant to nuclear monitoring. We determined that a salt mine collapse near Solikamsk, the Ural Mountains on 5 January 1995 was most likely a mine collapse instead of an underground explosions. (3) This study was carried out jointly by the Seismology Group of the University of Colorado and the Russian team from the Int'l Institute of Earthquake Prediction Theory and Math. Geophysics. We developed a new technique to identify a seismic event based on simultaneous inversion of surface wave amplitude spectra and signs of first motions of body wave. We applied this technique to several events near the Chinese test site at Lop Nor and demonstrated significant differences in source parameters characterizing explosions and natural earthquakes in this region

The Conclusions :
Results of this study can be summarized as follows:
• We developed a new approach to the identification of seismic events based on analysis of surface wave spectra and senses of the first motion. The validation of this technique at data from several events which occurred in Western China provided promising results
• We found several features characterizing tectonic release due to the explosion source which may help to identify possible explosions…….
• The statistical significance of these indicators will be determined after further analysis covering available data sets for several test sites

This document is linked to the Vela Incident (scientific reviews)

[edit on 30-11-2007 by frozen_snowman]