Infrasound Signals from Repeating Detonations at the

Utah Test and Training Range

Recorded in North America

J. Roger Bowman and Gordon Shields

Science Applications International Corporation

Infrasound Signals from Repeating Detonations at the

Utah Test and Training Range

Recorded in North America

J. Roger Bowman and Gordon Shields

Science Applications International Corporation

Presented at the Infrasound Technology WorkshopBermuda

November 3-7, 2008 Approved for public release; distribution unlimited

 DISCLAIMER

“The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either express or implied, of the U.S. Army Space and Missile Defense Command or the

U.S. Government.”

2

IntroductionIntroduction

Objective Detonations Infrasound data Observations Modeling Conclusions

3

ObjectiveObjective

Explore seasonal variation of infrasound propagation on a variety of paths

4

Utah Test and Training RangeUtah Test and Training Range

ICBM motors are regularly disposed of by detonation at the Utah Test and Training Range (UTTR) west of Salt Lake City, Utah

Yields: 40-80 t

Open burn/open detonation of a missile of a missile motor at the UTTRmotor at the UTTR

http://www.youtube.com/watch?v=qmAkZMdcJh4

Launch of a Poseidon Launch of a Poseidon missile, one type being missile, one type being disposed of at UTTR disposed of at UTTR

since 1995since 1995

5

Detonation DistributionDetonation Distribution

148 explosions in 4+ “years”

Origin times from seismic Origin times from seismic data kindly provided by data kindly provided by Relu Burlacu at the Relu Burlacu at the University of UtahUniversity of Utah

6

Infrasound DataInfrasound Data

June 22, 2004 at 17:12:29June 22, 2004 at 17:12:29Observed primarily at stations west of UTTR Observed primarily at stations west of UTTR

April 12, 2004 at 20:59:00April 12, 2004 at 20:59:00Observed primarily at stations east of UTTR Observed primarily at stations east of UTTR

We analyzed waveforms from all We analyzed waveforms from all infrasound arrays in North America infrasound arrays in North America

for all 148 detonations for all 148 detonations

7

Infrasound Signal AnalysisInfrasound Signal Analysis

Multiple (3-8), discrete Multiple (3-8), discrete arrivals are a key arrivals are a key

feature of signals from feature of signals from UTTR detonationsUTTR detonations

Attributes are measured separately for each arrival

8

Detection of DetonationsDetection of Detonations

DetectedNot DetectedNo Data Signals detected to the west

in the “summer”

Signals detected to the east in the “non-summer”

Signals detected at all stations except TXIAR (I59US not in operation)

Signals detected at PDIAR in “all seasons” (but lower coherence in “summer”)

Signals detected for 138 of 148 detonations

9

Seasonal Variation in Celerity: The BestSeasonal Variation in Celerity: The Best

Each of 4 or 5 arrival sets makes an arcuate pattern with day of year, with maximum celerity mid-summer

2004 2005 2004-200720072006

Seasonal pattern is similar from year to year

Arrivals are color coded by sequence number (gray when not part of the normal sequence).

10

Seasonal Variation in Celerity : The RestSeasonal Variation in Celerity : The Rest

Consistent with arcuate pattern at other stations to the west, but no clearly defined sequence of arrivals

Three arrivals don’t make a pattern!

As many as 8 arrivals per sequence

Slower, less coherent arrivals in the summer

11

Seasonal Variation in Back Azimuth ResidualSeasonal Variation in Back Azimuth Residual

Black: coherence ≥ 0.5; Gray: coherence < 0.5

2004 2005 2004-200720072006

Concave down

Concave up?

12

Modeling: Travel TimesModeling: Travel Times

G2S-07 atmospheric G2S-07 atmospheric specifications kindly specifications kindly provided by Doug Drob provided by Doug Drob of NRLof NRL

Predicted seasonal cutoff and time variation of stratospheric arrivals match observations

Fractional year Fractional year

13

Modeling: Back Azimuth ResidualsModeling: Back Azimuth Residuals

• Minimum observed back azimuth residuals are consistent with predictions

• Observed residuals generally are significantly larger than predictions

14

Modeling: Signal AttenuationModeling: Signal Attenuation

Observed signal amplitudes are consistent with a theoretical attenuation model:

where r is range, α is an absorption loss value (0.005 for stratospheric return), and C a scaling factor for source size.

rr

Camp 202

101

15

Modeling: Repeating Arrivals at I10CAModeling: Repeating Arrivals at I10CAG2S-07 cannot match the G2S-07 cannot match the observed multiple arrivalsobserved multiple arrivals

A model with a faster stratospheric duct A model with a faster stratospheric duct and a shallower tropospheric gradient best and a shallower tropospheric gradient best

matches the observed multiple arrivalsmatches the observed multiple arrivals

G2S-07 sound speed (unmodified)

Assumed along-path wind

Effective sound speed

G2S-07 along-path wind

Ray fan is Ray fan is broadenedbroadened

Range of bounce Range of bounce points is broadenedpoints is broadened

16

ConclusionsConclusions

Repeating detonations at UTTR make excellent atmospheric probes

40-80 t shots are commonly detected at ranges of 550 – 1650 km

Detection rates vary seasonally and depend on direction from source

Seasonal variations of celerity and back azimuth are consistent with predictions using G2S-07 specifications

Observations of multiple arrivals imply faster stratospheric duct and shallower tropospheric gradient than specified in G2S-07