Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Bulletin of the Seismological Society of America Email Content Delivery
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Bulletin of the Seismological Society of America; August 1992; v. 82; no. 4; p. 1889-1909
© 1992 Seismological Society of America
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by POWELL, C. A.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Seismic noise in northcentral North Carolina

CHRISTINE A. POWELL

MACCARTHY GEOPHYSICAL OBSERVATORY DEPARTMENT OF GEOLOGY, CB#3315
UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL, CHAPEL HILL, NORTH CAROLINA 27599-3315

Abstract

Ambient seismic noise in the frequency range 0.5 to 7 Hz is investigated for a portion of northcentral North Carolina. Three-component, digital data were collected as part of the state's bid for the Superconducting Super Collider. Stations were established along the proposed collider ring position and were intentionally located near sources of transient vibration. The absence of transient vibrations over all or a significant portion of the recording interval at six stations allowed seismic noise to be investigated.

Noise spectra display similarities in shape; all spectra decay with approximately constant slope (roughly f–3) below 1 Hz and all flatten in the frequency range 2 to 3 Hz. Vertical-component spectra decay with roughly constant slope (f–2.1) for f > 4 Hz. At most stations, spectral levels for horizontal components are greater than vertical-component levels for f > 4 Hz. Vertical-component spectra are similar in shape and magnitude to vertical spectra computed for RSTN station RSCP.

The most likely source for the ambient seismic noise is higher-mode surface waves produced by cultural activity. Ambient noise cannot be attributed to system noise or to the direct effects of traffic. Higher-mode surface waves are suggested by low coherence values computed for orthogonal components and extremely complex particle motion diagrams. Large horizontal particle motions and high spectral levels for horizontal components suggest that a significant portion of the noise, particularly for f > 4 Hz, is being produced by Love waves. Rayleigh waves contribute to the noise in the band 2 to 3 Hz.






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Seismological Society of America