Assessment of Seismic and Infrasound Signals in Korea With Ground Truth
Abstract
A four-element, 1-km aperture seismo-acoustic array is being operated northeast of Seoul, Korea. Each element of the array consists of a GS-13 vertical seismometer (1 Hz) in a shallow borehole (approx. 10 m) and a low-frequency acoustic gauge connected to an 11-element hose array (7.6 m hoses) at the surface. The array is being used to assess the importance of co-located seismic and acoustic sensors for the purposes of: (1) quantifying wind as a source of seismic and acoustic noise; (2) constraining propagation path effects in the atmosphere and solid earth; (3) locating the sources of the waves; (4) characterizing the source type. Combined analysis of the seismic and acoustic data can be particularly important in identifying sources of industrial blasting. Seismic noise estimates illustrate a level that is only slightly above the low noise model on average. Acoustic noise levels resolve the microbaroms during low noise times but document a nearly 50 dB increase in noise during the windiest periods. Infrasonic noise in the 0.01 to 5 Hz band increases rapidly with wind velocity. The seismic noise shows little or no dependence on wind velocity. Analysis of the data suggests that there are many more acoustic signals than seismic (4-10 times). The majority of the acoustic signals occurs during working hours and are constrained to several narrow azimuth ranges. These observations suggest that the signals are man made. Approximately 1/4 of all seismic signals are associated with an acoustic arrival. The seismo-acoustic observations come from sources in the 30 to 200 km range and occur during working hours, local time. The 30 to 200 km observation distance is surprising in that average atmospheric velocity models predict no acoustic returns in this range. Average atmospheric models modified by meteorological data for the troposphere indicate the possibility of ducting in the troposphere as an explanation for these arrivals.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2001
- Accession Number
- ADA527338
Entities
People
- Brian Stump
- Chris Hayward
- Il-young Che
- Jeong-soo Jeon
- Myung-soon Jun
- Sara M. House
- Tae-sung Kim
Organizations
- Southern Methodist University