Estimation of Explosion Moments at Mururoa and Tectonic Release Orientations at Novaya Zemlya
Abstract
A least-squares moment tensor inversion technique is applied to 10 presumed nuclear explosions from the French Polynesian test site at Mururoa. Our results indicate that tectonic release typically is quite low (with F 's ranging from 0.9 to .46) and makes little contribution to event moment. Assuming an oblique thrust orientation for the tectonic release mechanism, the delta m sub b between Mururoa and NTS is roughly .2 to .25 magnitude units. Finally, yield estimates generated from three different magnitude-yield relations are compared and found reasonably close to one another and to the one known yield value. A search technique is used to jointly invert multiple types of data for six Northern Novaya Zemlya presumed nuclear explosions to find the average tectonic release orientation (strike, slip, and dip). P waveform, SH polarity, and surface wave data were used in the inversion, but SV amplitude data had too much scatter to be included. The available data was insufficient to distinguish between a thrust and an oblique normal orientation. An improved distribution of stations recording SH polarities, more accurate SV data, and/or geologic knowledge of the source region could provide enough additional information to determine the orientation. The presence of multiple, substantially different orientations that fit waveform, surface wave, and polarity data suggests that more effort needs to be made to systematically search the model space for alternative solutions in studies involving both isotropic and double couple sources.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1990
- Accession Number
- ADA228258
Entities
People
- G. R. Mellman
- M. Henry
- Wayne C. Tucker