| Abstract: | INTRODUCTION
This report presents the results of a series of computer simulations of potential errors in test data, which might be obtained when conducting side-by-side comparisons of seismometers. These results can be used as guides in estimating potential sources and magnitudes of errors one might expect when analyzing real test data.
First, the derivation of a direct method for calculating the noise levels of two sensors in a side-by-side evaluation is repeated and extended slightly herein. This bulk of this derivation was presented previously (see Holcomb 1989); it is repeated here for easy reference.
This method is applied to the analysis of a simulated test of two sensors in a side-by-side test in which the outputs of both sensors consist of white noise spectra with known signal-to-noise ratios (SNR‘s). This report extends this analysis to high SNR‘s to determine the limitations of the direct method for calculating the noise levels at signal-to-noise levels which are much higher than presented previously (see Holcomb 1989).
Next, the method is used to analyze a simulated test of two sensors in a side-by-side test in which the outputs of both sensors consist of bandshaped noise spectra with known signal-to-noise ratios. This is a much more realistic representation of real world data because the earth‘s background spectrum is certainly not flat.
Finally, the results of the analysis of simulated white and bandshaped side-by-side test data are used to assist in interpreting the analysis of the effects of simulated azimuthal misalignment in side-by-side sensor evaluations. A thorough understanding of azimuthal misalignment errors is important because of the physical impossibility of perfectly aligning two sensors in a real world situation. The analysis herein indicates that alignment errors place lower limits on the levels of system noise which can be resolved in a side-by-side measurement. It also indicates that alignment errors are the source of the fact that real data noise spectra tend to follow the earth‘s background spectra in shape. |
| Genre: | USGS Numbered Series |
| ProdID: | 19385 |
| Citation Author: | Holcomb, L. Gary |
| Citation Contributing Office: | USGS Albuquerque Seismological Laboratory |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | - |
| Citation Editor: | |
| Citation End Page: | |
| Citation Issue: | |
| Citation Keywords: | |
| Citation Language: | ENGLISH |
| Citation Larger Work Title: | |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | 41 p. |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | Geological Survey (U.S.) |
| Citation Series: | Open-File Report |
| Citation Series Code: | OFR |
| Citation Series Number: | 90-406 |
| Citation Search Results Text: | A Numerical Study of Some Potential Sources of Error in Side-by-Side Seismometer Evaluations; 1990; OFR; 90-406; Holcomb, L. Gary |
| Citation Start Page: | |
| Citation Volume: | |
| Citation Year: | 1990 |
| Type: | citation/reference |
| Text: | A Numerical Study of Some Potential Sources of Error in Side-by-Side Seismometer Evaluations; 1990; OFR; 90-406; Holcomb, L. Gary |
| URL (THUMBNAIL): | http://pubs.usgs.gov/of/1990/0406/report-thumb.jpg |
| URL (DOCUMENT): | http://earthquake.usgs.gov/regional/asl/pubs/files/ofr90-406.pdf |
| URL (DOCUMENT): | http://pubs.usgs.gov/of/1990/0406/report.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | Geological Survey (U.S.) |
