Locating Bolide Fragmentations Locating Bolide Fragmentations and Terminal Explosions using and Terminal Explosions using

Arrival times of Acoustic WavesArrival times of Acoustic Waves Wayne N. Edwards and Alan R. Wayne N. Edwards and Alan R.

HildebrandHildebrandDepartment of Geology & Geophysics, University of Calgary, Alberta, Department of Geology & Geophysics, University of Calgary, Alberta,

CanadaCanada

2003 AGU Infrasound Technology WorkshopOctober 29th, 2003

What is a Supracenter?What is a Supracenter?

Analogous to earthquake Analogous to earthquake location in the solid Earthlocation in the solid Earth

ComplicationsComplications P wave velocities slowerP wave velocities slower Winds vary in magnitude & Winds vary in magnitude &

direction with altitudedirection with altitude Fireball explodes – point Fireball explodes – point

source of finite durationsource of finite duration Wavefront propagates to Wavefront propagates to

ground where ground where seismometers, seismometers, microphones & infrasound microphones & infrasound arrays record its arrivalarrays record its arrival

Photo by: Brad Gledhill

Potential Arrivals Potential Arrivals depend on distance depend on distance of receiver stationof receiver station

a.a. Direct arrivalsDirect arrivals

b.b. Ducted wavesDucted waves

c.c. Thermospheric Thermospheric returnsreturns

d.d. Stratospheric returnsStratospheric returns

e.e. SkipsSkips

(Brown et al. 2003)Red Box shows region of direct arrivals

Propagation in the Propagation in the AtmosphereAtmosphere

Recognizing the Seismic Recognizing the Seismic SignalSignal

Duration: order of minutes longDuration: order of minutes long

Propagation: low trace velocities across arraysPropagation: low trace velocities across arrays

A – Slow initial riseA – Slow initial rise– ground roll arrivalsground roll arrivals

B – Prominent peakB – Prominent peak– direct atmosphericdirect atmospheric– Terminal Burst or Terminal Burst or Sonic Boom?Sonic Boom?

C – Long drawn out C – Long drawn out tailtail

– higher altitude higher altitude sourcessources• e.g. Early e.g. Early fragmentationfragmentation

A

B

C

Finding a SolutionFinding a Solution

1 – Identify & pick station arrival times1 – Identify & pick station arrival times2 – Construct model atmosphere 2 – Construct model atmosphere Acoustic velocity Acoustic velocity

3 – 3 – Assume that all arrivals from the same Assume that all arrivals from the same eventevent::

TTAA = T = TBB = T = TCC = T = TDD = … = T = … = Tbb = Initial time of = Initial time of burstburst

Finding a SolutionFinding a Solution5 – Choose a position: ray trace to receivers5 – Choose a position: ray trace to receivers

6b – Use a known, observed occurrence time6b – Use a known, observed occurrence time•Earth-observing satellitesEarth-observing satellites•Recorded videoRecorded video

N

icalcobsb ii

TTN

T1

(Nelson & Vidale 1990)

6a – Find the mean time of occurrence6a – Find the mean time of occurrence

7 – Calculate station traveltime residuals7 – Calculate station traveltime residuals

8 – Vary position to minimize the mean 8 – Vary position to minimize the mean residualresidual

Previous Supracenter Previous Supracenter LocationsLocations Have only treated atmosphere as an isotropic Have only treated atmosphere as an isotropic

velocity medium. velocity medium. Johnston 1987: Missile silo explosion & supersonic Johnston 1987: Missile silo explosion & supersonic

aircraftaircraft Qamar 1995: Fireball terminal burstsQamar 1995: Fireball terminal bursts Borovička and Kalenda 2003: Fireball Borovička and Kalenda 2003: Fireball

fragmentationfragmentation Assumed atmosphere is static in most casesAssumed atmosphere is static in most cases

Result:Result:

Solutions may mis-locate an event by several Solutions may mis-locate an event by several kilometers depending upon wind conditions kilometers depending upon wind conditions in the atmosphere at the time of the event.in the atmosphere at the time of the event.

Ray Tracing Ray Tracing ComplicationsComplications

Winds Winds Ray propagation becomes direction Ray propagation becomes direction dependantdependant

Winds perpendicular to azimuth add motion Winds perpendicular to azimuth add motion outside of azimuth plane outside of azimuth plane RESULT: RESULT: rays bend!rays bend! Azimuth & Elevation angle UNKNOWNAzimuth & Elevation angle UNKNOWN

Solution: Solution: Modified Tau-Modified Tau-pp Equations Equations

(Garc(Garcéés et al. 1998)s et al. 1998) Iteratively refining “Ray Net”Iteratively refining “Ray Net” to identify ray orientationto identify ray orientation angles connecting sourceangles connecting source to receiverto receiver

Structure of Traveltime Structure of Traveltime ErrorError

(Ray tracing vs. Analytic)(Ray tracing vs. Analytic)

30 km Source in 30 km Source in a windy,a windy,(45 m/s from the (45 m/s from the North) North) Isotropic Isotropic (300 m/s) (300 m/s) Atmosphere Atmosphere (15% of Local Sound (15% of Local Sound Speed Speed oror L.S.S.) L.S.S.)

Maximum Error: Maximum Error: ~0.0048% of ~0.0048% of TraveltimeTraveltime

Analytic ModelAnalytic Model

The SUPRACENTER ProgramThe SUPRACENTER Program

Uses a stratified model of the Uses a stratified model of the atmosphereatmosphere Local or nearby radiosonde soundingsLocal or nearby radiosonde soundings Atmospheric models (e.g. MSIS-E, HWM)Atmospheric models (e.g. MSIS-E, HWM) 1978 U.S. Standard Atmosphere (as option)1978 U.S. Standard Atmosphere (as option)

Includes the effects of winds as it traces Includes the effects of winds as it traces rays!rays! NOTNOT a correction for wind applied after a correction for wind applied after

locating an otherwise static solution.locating an otherwise static solution.

Simplifications & Simplifications & AssumptionsAssumptions

Geometrical rays Geometrical rays - diffraction is minimal over the travel time of a ray- diffraction is minimal over the travel time of a ray

Atmospheric motions are predominantly horizontalAtmospheric motions are predominantly horizontal- (i.e. vertical motions are negligible)- (i.e. vertical motions are negligible) Horizontal variations in temperature Horizontal variations in temperature and windand wind are negligible.are negligible. Atmosphere is approximated by discrete layers,Atmosphere is approximated by discrete layers,

each with its own characteristic temperature andeach with its own characteristic temperature and wind vector.wind vector. Use only direct air arrivals.Use only direct air arrivals. (i.e. receivers (i.e. receivers ≤≤ 100 km to the event epicenter) 100 km to the event epicenter)

Flat Earth ApproximationFlat Earth Approximation

Testing SUPRACENTER …Testing SUPRACENTER …

El Paso Superbolide, October 9El Paso Superbolide, October 9thth 1997. 1997. Mt. Adams Fireball, January 25Mt. Adams Fireball, January 25thth 1989. 1989.

MovMovávka meteorite fall, May 6ávka meteorite fall, May 6thth 2000. 2000.

Three seismically detected fireball events Three seismically detected fireball events were chosen where independent solutions were chosen where independent solutions existed.existed.

Two Historical:Two Historical:

One Recent:One Recent:

Case Study #1: El Paso Case Study #1: El Paso Superbolide October 9Superbolide October 9thth, ,

19971997 Daytime fireball at local noon hour ~18:47:15 Daytime fireball at local noon hour ~18:47:15

UTUT Many eyewitnessesMany eyewitnesses 19 photographs of the dust cloud19 photographs of the dust cloud 6 video recordings6 video recordings 8 seismic detections & 2 infrasonic8 seismic detections & 2 infrasonic

Terminal burst of fireball produced a circular Terminal burst of fireball produced a circular dust cloud ~1 km in diameter dust cloud ~1 km in diameter supersonic supersonic shockshock

Photographic observations produced an Photographic observations produced an accurate determination of the position for the accurate determination of the position for the terminal explosion. (Hildebrand terminal explosion. (Hildebrand et al.et al. 1999) 1999)

Distribution of StationsDistribution of Stations Non-ideal linear orientation (NW-SE)Non-ideal linear orientation (NW-SE) Long distances between stationsLong distances between stations

Limited # of potential stations with direct Limited # of potential stations with direct arrivalsarrivals

Atmospheric SoundingAtmospheric Sounding

Radiosonde DataRadiosonde Data• largest winds at ~15 km where local sound speed is largest winds at ~15 km where local sound speed is lowestlowest• winds predominantly from WSW below 20 kmwinds predominantly from WSW below 20 km• prominent wind shearing at ~30 kmprominent wind shearing at ~30 km

Comparison of SolutionsComparison of Solutions Hildebrand Hildebrand et al.et al. (1999) (1999)

Observed Event time ~18:47:15 UTObserved Event time ~18:47:15 UT 31.8031.80ooN, 106.06N, 106.06ooW at ~28.5 km altitudeW at ~28.5 km altitude Derived from eyewitness reports, photographic Derived from eyewitness reports, photographic

and video recordsand video records

SUPRACENTERSUPRACENTER 31.79031.790ooN, 106.080N, 106.080ooW at 27.6 km a.s.l. + 0.5 km W at 27.6 km a.s.l. + 0.5 km

shockshock Occurrence time constrained to 18:47:15 UTOccurrence time constrained to 18:47:15 UT Avg. residual of 0.240 secondsAvg. residual of 0.240 seconds ~2.1 km WSW from Hildebrand ~2.1 km WSW from Hildebrand et al.et al. solution solution

found through independent methodsfound through independent methods

N

Case Study #2: Mt. Case Study #2: Mt. Adams Fireball January Adams Fireball January

2525thth, 1989., 1989. Bright Daytime fireball at local noon hour. Bright Daytime fireball at local noon hour.

12:51 pm, Pacific Standard Time12:51 pm, Pacific Standard Time NW to SE track over Puget Sound, NW to SE track over Puget Sound,

Washington ending near the NW flank of Washington ending near the NW flank of Mt. Adams (Pugh 1990).Mt. Adams (Pugh 1990).

During decent fireball split in two with each During decent fireball split in two with each fragment producing its own terminal burst. fragment producing its own terminal burst.

Both bursts were recorded by 26 seismic Both bursts were recorded by 26 seismic stations (Qamar 1995) of the Pacific stations (Qamar 1995) of the Pacific Northwest Seismic Network.Northwest Seismic Network.

January 25January 25thth, 1989 Model , 1989 Model AtmosphereAtmosphere

Radiosonde Data + 1978 U.S. Std Atmosphere + Radiosonde Data + 1978 U.S. Std Atmosphere + HWMHWM- dual temperature inversions- increased winds correlate to region of lowest temperature- Predominantly NNW winds

Comparison of SolutionsComparison of Solutions Qamar (1995)Qamar (1995)

Burst A: 46.435Burst A: 46.435ooN, 122.094N, 122.094ooW at 35.1 W at 35.1 ± 1.0± 1.0 km km Height @ 20:51:10.1 UTHeight @ 20:51:10.1 UT

Burst B: 46.396Burst B: 46.396ooN, 122.062N, 122.062ooW at 30.4 W at 30.4 ±± 0.7 km 0.7 km Height @ 20:51:10.9 UTHeight @ 20:51:10.9 UT

SUPRACENTERSUPRACENTER Burst A: 46.460Burst A: 46.460ooN, 122.096N, 122.096ooW at 34.62 km a.s.l @ W at 34.62 km a.s.l @

20:51:14.5 UT20:51:14.5 UT Avg. residual: 0.925 sec. Stations Untimed: 5Avg. residual: 0.925 sec. Stations Untimed: 5 ~2.7 km NNW of Qamar’s solution~2.7 km NNW of Qamar’s solution

Burst B: 46.418Burst B: 46.418ooN, 122.065N, 122.065ooW at 29.82 km a.s.l @ W at 29.82 km a.s.l @ 20:51:15.1 UT20:51:15.1 UT

Avg. residual: 0.903 sec. Stations Untimed: 5Avg. residual: 0.903 sec. Stations Untimed: 5 ~2.5 km NNW of Qamar’s solution~2.5 km NNW of Qamar’s solution

Differences?Differences?

Low winter atmospheric temperaturesLow winter atmospheric temperatures lower sound speeds lower sound speeds bursts at lower heights bursts at lower heights later times later times

Without independent measure of Without independent measure of fireball’s time of occurrence, fireball’s time of occurrence, determination of which is correct determination of which is correct event time is unlikely to be resolvedevent time is unlikely to be resolved

Mt. Adams Fireball Mt. Adams Fireball TrajectoryTrajectory

Trajectory Parameters:Trajectory Parameters:

Azimuth: 152Azimuth: 152oo

Elevation: 43Elevation: 43oo

Velocity: 11.7 km/sVelocity: 11.7 km/s

Consistent with investigation of Pugh Consistent with investigation of Pugh (1990):(1990):““Entered atmosphere over Puget Sound Entered atmosphere over Puget Sound … disruption over northwest flank of Mt. … disruption over northwest flank of Mt. Adams”Adams”

ConclusionsConclusions1.1. Using arrivals of acoustic waves at the surface Using arrivals of acoustic waves at the surface

and realistic ray tracing and realistic ray tracing it is possibleit is possible to locate to locate atmospheric explosions.atmospheric explosions.

2.2. Significant position “Significant position “driftdrift” does occur when ” does occur when strong unidirectional winds are present.strong unidirectional winds are present.

3.3. Position “Position “driftdrift” can be on the order of several ” can be on the order of several kilometres kilometres width’s of meteorite strewn fields width’s of meteorite strewn fields

4.4. Method is independent of the time of the Method is independent of the time of the fireballfireball

5.5. SUPRACENTER demonstrates both consistency SUPRACENTER demonstrates both consistency with and improvement over the simple with and improvement over the simple isotropic (average velocity) atmosphere isotropic (average velocity) atmosphere treatments of the past.treatments of the past.

ImplicationsImplications

Potential for 24 hr monitoring for fireballsPotential for 24 hr monitoring for fireballs More monitoring stations neededMore monitoring stations needed Simple as installing a microphone + recorder on Simple as installing a microphone + recorder on

current & future fireball camera networkscurrent & future fireball camera networks How does this help meteorite recovery efforts?How does this help meteorite recovery efforts?

Better estimates for locations of potential strewn Better estimates for locations of potential strewn fields fields

Potential recovery of more freshly fallen meteoritesPotential recovery of more freshly fallen meteorites Another tool for fireball trajectory trackingAnother tool for fireball trajectory tracking Accurate location Accurate location Constrain energy Constrain energy

calibrationscalibrations

Future WorkFuture Work Extension of supracenter location Extension of supracenter location

method to stratospheric and method to stratospheric and thermospheric returnsthermospheric returns

Allow distant stations to be used in Allow distant stations to be used in solutionsolution

Provide more constraint to poorly Provide more constraint to poorly sampled eventssampled events

Requirements:Requirements: 1.1. Choice between multiple arrivalsChoice between multiple arrivals

• Path that minimizes the station residualPath that minimizes the station residual

ReferencesReferencesGarcGarcéés, M.A., Hansen, R.A. and Lindquist, K., G. (1998) Traveltimes for s, M.A., Hansen, R.A. and Lindquist, K., G. (1998) Traveltimes for

infrasonic waves propagating in a stratified atmosphere, infrasonic waves propagating in a stratified atmosphere, Geophysical Geophysical Journal InternationalJournal International, , 135135, pp. 255-263., pp. 255-263.

HildebrandHildebrand A., Brown P., Crawford D., Boslough M., Chael E., Revelle D., A., Brown P., Crawford D., Boslough M., Chael E., Revelle D., Doser D., Tagliaferri E., Rathbun D., Cooke D., Adcock C. and Karner J. Doser D., Tagliaferri E., Rathbun D., Cooke D., Adcock C. and Karner J. (1999) The El Paso Superbolide of October 9, 1997, In (1999) The El Paso Superbolide of October 9, 1997, In Lunar and Lunar and Planetary Science XXXPlanetary Science XXX, , Abstract #1525Abstract #1525, Lunar and Planetary Institute, , Lunar and Planetary Institute, Houston (CD-ROM).Houston (CD-ROM).

Johnston C. (1987) Air blast recognition and location using regional seismographic Johnston C. (1987) Air blast recognition and location using regional seismographic networks, networks, Bulletin of the Seismological Society of AmericaBulletin of the Seismological Society of America, , 7777, no.4, pp. 1446-, no.4, pp. 1446-1456.1456.

Nelson G. and Vidale J. (1990) Earthquake locations by 3D finite-difference Nelson G. and Vidale J. (1990) Earthquake locations by 3D finite-difference traveltimes, traveltimes, Bulletin of the Seismological Society of AmericaBulletin of the Seismological Society of America, , 8080, no.2, pp. 395-, no.2, pp. 395-410. 410. 

Pugh R. (1990) The Mt. Adams, Washington Fireball of January 25, 1989, Pugh R. (1990) The Mt. Adams, Washington Fireball of January 25, 1989, MeteoriticsMeteoritics, , 2525, p. 400. , p. 400.

Qamar A. (1995) Space Shuttle and Meteoroid – Tracking Supersonic Objects in the Qamar A. (1995) Space Shuttle and Meteoroid – Tracking Supersonic Objects in the Atmosphere with Seismographs, Atmosphere with Seismographs, Seismological Research LettersSeismological Research Letters, , 6666, no.5, pp. 6-, no.5, pp. 6-12.12.

Case Study #3: Morávka Case Study #3: Morávka Meteorite Fall May 6Meteorite Fall May 6thth, 2000, 2000

Bright daytime fireball observed by 1000’s of Bright daytime fireball observed by 1000’s of eyewitnesses and 3 amateur video’s (Borovička eyewitnesses and 3 amateur video’s (Borovička et al. 2003).et al. 2003).

Fireball produced a cascade of individual Fireball produced a cascade of individual fragmentations while passing directly over a fragmentations while passing directly over a seismic network.seismic network.

Arrivals for 12 fragmentation events were Arrivals for 12 fragmentation events were identified from complex amplitudes and located identified from complex amplitudes and located using an isotropic method by Borovička and using an isotropic method by Borovička and Kalenda (2003).Kalenda (2003).

Both the fireball’s trajectory & pre-fall orbit were Both the fireball’s trajectory & pre-fall orbit were well determined through video analysis well determined through video analysis (Borovička et al. 2003).(Borovička et al. 2003).

Stations & Arrival timesStations & Arrival times

• 6 of 12 6 of 12 Fragmentation Fragmentation acoustic arrivals acoustic arrivals identified by identified by Borovička & Kalenda Borovička & Kalenda from 11 station from 11 station recordsrecords

• Atmospheric model Atmospheric model of Brown et al. of Brown et al. (2003) constructed (2003) constructed from a nearby from a nearby radiosonde release radiosonde release ((Poprad, SlovakiaPoprad, Slovakia))

1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5Tim e (seconds after 11:53:00 U T)

1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5

C H O

H AV

C SM

KVE

M AJ

C SA

R AJ

LU T

PR S

BM Z

R AC

CEFGKL

(Borovička and Kalenda 2003)(Borovička and Kalenda 2003)

Model Atmosphere to 50 Model Atmosphere to 50 kmkm

(Brown et al. 2003)(Brown et al. 2003)

Winds are relatively light. Peak @ 13.2 m/s (4.4% of Winds are relatively light. Peak @ 13.2 m/s (4.4% of L.S.S.)L.S.S.)Wind direction is not unidirectional – generally from the Wind direction is not unidirectional – generally from the SouthSouth

Result:Result: “ “Wind driftWind drift” should be minimal for ” should be minimal for supracenterssupracenters

Comparison of SolutionsComparison of Solutions

Fit to satellite observed time of 11:51:52.5 UTFit to satellite observed time of 11:51:52.5 UT Very little wind “Very little wind “driftdrift”: ~0.1 – 1 km”: ~0.1 – 1 km Difference between Borovička & Kalenda & Difference between Borovička & Kalenda &

SUPRACENTER solutions: 0.4 – 1.5 kmSUPRACENTER solutions: 0.4 – 1.5 km Event K: repositioned ~1.5 km to the Event K: repositioned ~1.5 km to the

SouthwestSouthwest

Lat. Lat. (N)(N)

Long.Long.(E)(E)

Alt.Alt.(km)(km)

Lat. Lat. (N)(N)

Long.Long.(E)(E)

Alt.Alt.(km)(km)

CC

EE

FF

GG

KK

LL

49.986249.9862

49.949949.9499

49.928349.9283

49.918049.9180

49.874849.8748

49.810949.8109

18.476918.4769

18.481418.4814

18.488718.4887

18.488718.4887

18.496718.4967

18.510218.5102

35.42035.420

33.53033.530

32.66032.660

32.18032.180

30.42030.420

28.22028.220

49.972849.9728

49.943149.9431

49.922149.9221

49.914149.9141

49.862549.8625

49.805249.8052

18.477118.4771

18.478718.4787

18.486718.4867

18.488518.4885

18.485618.4856

18.508518.5085

3535..450450

3333..350350

3232..580580

3232..100100

3030..550550

2828.6.62525

Borovička & Kalenda (2003) SUPRACENTER

~1.5 km~1.5 km

(2003)

CC

EEFF

GG

KK

LL

Morávka Fireball TrajectoryMorávka Fireball Trajectory

Trajectory Parameters via SUPRACENTERTrajectory Parameters via SUPRACENTER

Azimuth: 171.8Azimuth: 171.8oo

Elevation: 18.9Elevation: 18.9oo

Determined through Video Analysis Determined through Video Analysis (Borovička et (Borovička et al. 2003)al. 2003)

Azimuth: 175.5Azimuth: 175.5oo

Elevation: 20.4Elevation: 20.4oo

Difference?Difference?Fragments travelling along slightly different Fragments travelling along slightly different trajectories.trajectories.

ororMis-identification of acoustic arrivals?Mis-identification of acoustic arrivals?

Comparison to Kunovice Comparison to Kunovice VideoVideo

Fragmentations show Fragmentations show alignment improvementalignment improvement

New K position at start of New K position at start of 11stst stream of fragments stream of fragments

L – misalignment likely due L – misalignment likely due to later occurrence timeto later occurrence time

Fit L time to ~13Fit L time to ~13oo elevation elevation 300 m lower300 m lower Occ. time: +0.91 sec.Occ. time: +0.91 sec.

Fireball Velocity: 22.1 km/sFireball Velocity: 22.1 km/s

From video analysis: 22.5 From video analysis: 22.5 km/skm/s

(Borovička et al. 2003)(Borovička et al. 2003)

NOTE: Small squares: positions of individual fragmentsmapped from the Kunovice video

-300m

ReferencesReferencesBorovička J., Spurny P., Kalenda P., and Borovička J., Spurny P., Kalenda P., and

Tagliaferri E. Tagliaferri E. ((2002003)3) The Morávka Meteorite The Morávka Meteorite Fall I: Description of the events and Fall I: Description of the events and determination of the fireball trajectory and determination of the fireball trajectory and orbit from video records, orbit from video records, Meteoritics & Meteoritics & Planetary SciencePlanetary Science, In Press., In Press.

Borovička, J. and Kalenda, P. (200Borovička, J. and Kalenda, P. (20033) Meteoroid ) Meteoroid dynamics and fragmentation in the dynamics and fragmentation in the atmosphere, atmosphere, Meteoritics and Planetary Meteoritics and Planetary ScienceScience, , In Press.In Press.

Brown P., Kalenda P., ReVelle D., and Borovička J. Brown P., Kalenda P., ReVelle D., and Borovička J. ((2002003)3) The Morávka Meteorite Fall II: The Morávka Meteorite Fall II: Interpretation of Infrasonic and Seismic Data, Interpretation of Infrasonic and Seismic Data, Meteoritics & Planetary ScienceMeteoritics & Planetary Science, In Press. , In Press.