RESUMEN
The accuracy of input meteorological data can significantly impact the successful prediction of infrasound propagation at local to near-regional distances. These meteorological inputs are often derived from weather model simulations when event-specific measurements are not available, but the ideal spatial resolutions of these simulations have not been determined. This study seeks to identify the ideal horizontal resolutions for input meteorological data via infrasound simulations conducted with both range-dependent and -independent inputs. Outputs from the Weather Research and Forecasting (WRF) model at 1, 3, 5, and 15 km horizontal resolutions enable these investigations. The parabolic equation propagation model is used to calculate transmission loss for an impulsive signal and is compared against experimental data obtained from a series of 1 lb spherical, suspended C4 shots recorded on the infrasound array on the Waterways Experiment Station in Vicksburg, MS, occurring throughout the diurnal cycle with an overall propagation distance of 14.5 km. Simulations for morning and nighttime correctly predict signal detection and non-detection. Transitional times of day (dawn, evening) were partially successful. Changing horizontal resolutions in WRF incurred greater differences in prediction results than use of range-dependence vs -independence. No clear picture emerged regarding the optimal horizontal resolution for meteorological inputs.
RESUMEN
The Mississippi River Bridge in Vicksburg, Mississippi, is a seven-span cantilever bridge that is 1033 m long by 20.9 m wide and is part of the Interstate-20 corridor. On March 23, 2011, at approximately 14:30 CST, a barge moving downstream struck a pier of the bridge. An infrasound array located at the U.S. Army Engineer Research and Development Center (ERDC) detected the impact. Finite Element (FE) models were developed to investigate the structural behavior of the bridge due to the impact. The FE models identified events within the infrasound record that were possibly produced by the different modes of vibration of the bridge structure. The emerging technology of structural infrasound monitoring and the potential for using infrasound as a forensic tool is demonstrated with the results of the bridge-barge collision event and capability of deployment in the future.