Calibration formulae and values for velocity seismometers used in the 1998 Santa Clara Valley, California seismic experiment
Open-File Report
99-434
By: Allan Goddard Lindh, Jerry P. Eaton, Mary O’Neill Allen, John H. Healy, Samuel W. Stewart, and Lu Damerell
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Abstract
Eaton (1975), Bakun and Dratler (1976), Eaton (1977), Healy and O’Neil (1977), Asten (1977), Stewart and O'Neill (1980), Liu and Peselnick (1986), Eaton (1991), Rodgers et al. (1995), and many others (see Asten (1977) for a list of earlier references) have presented formulae for calculating the damped generator constant (or motor constant), and the damping constant (or fractional damping ratio) for magnetically damped velocity seismometers. Unfortunately the notation varies between authors, and not all the formulae allow for some of the significant variables -- differences in input impedance of the recording system in particular. This has become particularly relevant because the USGS seismic networks in California have traditionally set up their velocity sensors for the 10K Ohm impedance of the standard USGS analog telemetry systems (Eaton, 1977), but modern digital recording systems are usually set up with high input impedances, often of a megaohm or greater. Thus the nominal calibration values valid for USGS velocity sensors in their “normal” configuration are incorrect when they are recorded on other systems.
In this short note we have collected the relevant formulae needed, and computed the seismometer responses for the various velocity sensors used in the recent Santa Clara Valley Seismic Experiment (SCVSE, see Lindh et al., 1999).
Suggested Citation
Lindh, A.G., Eaton, J.P., O’Neill Allen, M., Healy, J., Stewart, S., Damerell, L., 1999, Calibration formulae and values for velocity seismometers used in the 1998 Santa Clara Valley, California seismic experiment: U.S. Geological Survey Open-File Report 99-434, Report: PDF, 7 p.; Report: DOC; 3 Tables, https://doi.org/10.3133/ofr99434.
ISSN: 2331-1258 (online)
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Calibration formulae and values for velocity seismometers used in the 1998 Santa Clara Valley, California seismic experiment |
| Series title | Open-File Report |
| Series number | 99-434 |
| DOI | 10.3133/ofr99434 |
| Year Published | 1999 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | Earthquake Science Center |
| Description | Report: PDF, 7 p.; Report: DOC; 3 Tables |
| Time Range Start | 1998-01-01 |
| Time Range End | 1998-12-31 |
| Country | United States |
| State | California |
| Other Geospatial | Santa Clara Valley |