Improved Infrasound Event Location
Abstract
The purpose of this project is to improve the ability to locate infrasound events by improving the Horizontal Wind Model (HWM) used in the prediction of infrasound observables, in particular, travel time and back azimuth. Our general approach uses new wind data to develop a higher-resolution and more accurate HWM and tests the performance of Ground to Space (G2S) specifications based on the new HWM, relative to those based on HWM-93 using a large set of ground-truth events. We assembled a preliminary data set of 180 events with which to exercise our statistical framework for testing the effect of atmospheric wind models on the accuracy of infrasound event locations. We also assembled wind data representing a 100-fold increase compared to those used for HWM-93 and incorporated these wind data into the mechanism used to generate improved HWMs. We applied this mechanism to construct a preliminary version of HWM-07, and demonstrated that this preliminary model displays some important features that were missing from HWM-93, such as wind velocities of up to 70 m/s at an altitude of 110 km. We created an efficient mechanism to trace rays through atmospheric models for a large suite of infrasound source-station pairs. Initially, we have based our generation of travel-time and back-azimuth predictions on the HARPA 3-D ray-tracing programs. We refined the statistical framework for testing the effect of atmospheric wind models on predictions and applied it to first arrivals for a preliminary data set of 251 source-receiver pairs from 108 events to evaluate and compare predictions made against the existing, baseline atmospheric specifications for our study, G2S and HWM-93/MSISE-00, on which it is based, above 50 km. As expected, we find that G2S more often and more accurately predicts stratospheric first arrival times and back azimuths, whereas the two models are both equally poor at predicting thermospheric arrival times and back azimuths.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2007
- Accession Number
- ADA519367
Entities
People
- Douglas P. Drob
- J. R. Bowman
- Michael S. O'brien
Organizations
- Leidos