SHORT-PERIOD MULTICOMPONENT STRAIN SYSTEM
Abstract
A five-component system of matched short-period strain and inertial seismographs at Wichita Mountains Observatory (WMO) was expanded to include a three-component system of matched long-period strain and inertial seismographs for recording large magnitude earthquakes. A data library and quality assurance procedure has been established. Calibration of the vertical strain seismometer with both a short rod and a rod of standard length (18 m) shows an apparent mechanical signal loss of 22 percent and a corresponding phase change as large as four degrees. A series of improvements has reduced the noise level of the long-period strain seismographs substantially. A site other than Garland, Texas, is being considered for noise suppression tests with a combination of vertical strain and inertial seismographs. From a recent study of the effect of low ratio of seismic signal to system noise on coherence, it is concluded that the possibility of suppressing microseisms in the region of 1 Hz with a combination of vertical strain and inertial seismographs cannot be evaluated unless either the generator constant of the vertical strain seismometer is increased, or tests be conducted at a site where the seismic noise level at 1 Hz is higher than at WMO.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 15, 1968
- Accession Number
- AD0834227
Entities
People
- R. C. Shopland
Organizations
- Geotech Instruments (United States)