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ABSTRACTS | ABSTRACT DETAILS

 

Author:Roger Bowman
Institution:SAIC, 10260 Campus Point Dr. San Diego, CA 92121
Email:roger.bowman@saic.com
Authors:Roger Bowman, Greg Beall, Doug Drob, Milton Garces, Claus Hetzer, Michael O’Brien, Gordon Shields
Abstract Title:

"Location and Characterization of Infrasonic Events"
Abstract:

We are working to improve and quantify the capability to locate and characterize infrasound events using data from infrasound stations of the International Monitoring System (IMS) and similar station in North America. The Prototype International Data Center (PIDC) used ray tracing to calculate an azimuthally varying infrasonic travel-time table for a representative Horizontal Wind Model (HWM) for each station and for each of the four seasons. However, the stratospheric winds are known to vary on time scales much shorter than seasonal, and diurnal variations are as significant a factor as seasonal. It is possible that variations over periods as short as several hours may significantly affect accuracy of locations. For this project we pursued a two-tier approach. For interactive processing, we used dynamically created travel-time tables based on the Ground-to-Space (G2S) meteorological model for the six-hour epoch closest to the time of the event to be analyzed. The G2S models merge numerical weather prediction results into the HWM and Mass Spectrometer, Incoherent Scatter-Extended-00 (MSISE-00) models. To avoid complexity in automatic processing, we have retained use of static travel-time tables. We calculated travel-time tables using the HWM and the MSISE-00 model for each station, month, and 6-hour period. We estimated the uncertainty of the static travel-time tables by computing statistics from G2S travel times. We employed the new travel-time tables in the standard location library, libloc, of the Nuclear Test Detection System. We will assess location estimates for events recorded by sufficient stations and azimuth estimates for those recorded by fewer stations using a data set of events with independent location estimates. We are also developing visualization tools to aid in characterizing infrasound signals and clutter.
Keywords:infrasound source location, infrasound source characterization

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