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Systems Check. Hydronynamics by Don Korycansky, http://www.ucolick.org/~kory/impacts. INFRASONIC SOURCE LOCATION USING THE TAU-P METHOD. Milton Garces and Claus Hetzer Infrasound Laboratory, University of Hawaii, Manoa Kent Lindquist Lindquist Consulting Douglas Drob

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Systems check

Systems Check

Hydronynamics by Don Korycansky, http://www.ucolick.org/~kory/impacts


Infrasonic source location using the tau p method

INFRASONIC SOURCE LOCATION USING THE TAU-P METHOD

Milton Garces and Claus Hetzer

Infrasound Laboratory, University of Hawaii, Manoa

Kent Lindquist

Lindquist Consulting

Douglas Drob

Naval Research Laboratory

2002 Infrasound Technology Workshop, Netherlands


Introduction

Introduction

  • Location accuracy determined by wind conditions and proper arrival identification

  • Apply tau-p model to telesonic events detected in the Pacific

  • April 23, 2001 and August 25, 2000 (Acapulco) Bolides

  • Bolides are not ideal sources, but options are limited


Wind structure

Wind Structure

Wind structure for the great circle path from April 23 source to IS59, Hawaii

Wind structure for the great circle path from April 23 source to IS53, Alaska


Phases

Phase ID

Description

Typical celerity of first arrival, m/s

iw

Guided wave propagating between the tropopause and the ground.

330-340

is

Guided wave propagating between the stratopause and the ground.

310-330

isd

Guided wave propagating in elevated waveguide between stratopause and the troposphere, and diffracted or scattered to the ground. May have higher frequency.

310-330

it

Guided wave propagating between the lower thermosphere and the ground.

280-300

itd

Guided wave propagating in elevated waveguide between the lower thermosphere and the troposphere, and diffracted or scattered to the ground.

280-300

It, Is, Iw

Direct arrival from the source to the receiver. May have high apparent phase velocity

N/A

Phases

Table 1. Preliminary phase identification nomenclature for long-range infrasonic propagation


Travel times azimuth deviation range and t surfaces 2000

Travel Times, Azimuth Deviation, Range, and t Surfaces (2000)

  • The next panel shows the travel time, range, azimuth deviation, and t as a function of arrival azimuth and incidence angle in the Poker Flat, AK. The t function is defined as t = T - pX, where T is the travel time, p is the conserved ray parameter, and X is the range (see for example Garcés et al., 1998). This figure was also generated by is_sphere.

  • The observed angle of arrival determines the three components of the infrasound wave-number vector - kew, kns, and kz.

  • These figures plot the first skip of a surface source. Multiple skips would correspond to integer multiples of these values.

  • Note that the t surface shows the monotonic, piecewise-continuous property of the t function, which makes it ideal for interpolation and operational implementation.


Characteristic surfaces for propagation at poker flat

Characteristic Surfaces for Propagation at Poker Flat


Tau9 1

Tau9.1


Turning slowness

Turning Slowness


2d model

2D Model

1D Model Output

This is where tau comes into play


Great balls of fire match origin time

Great Balls of Fire: Match Origin Time

Satellite (LO) and infrasonic (LA_DL2) location for the Acapulco bolide. The observed arrival azimuths at infrasound arrays IS08. IS25, IS53, DLIAR, and IS59 are shown as red lines.

Satellite (LO) and infrasonic (LA_S1) location for the April 23, 2001 bolide. The observed arrival azimuths at infrasound arrays IS53, IS57, and IS59 are shown as red lines.


April 23 bolide

Source

it

Lat (N)

itd

Lon (E)

isd

Origin Time (Epoch)

Lat error (deg)

Lon error (deg)

Time error (s)

IS53

0.268

0.284

0.292

LO1

27.9

-133.89

988006355

0

0

0

IS57

0.278

0.292

0.328

LA_S1

28.07

-135.09

988006347

0.17

-1.2

-8

IS59

0.284

0.3

0.311

LA_S2

27.79

-133.42

988006145

-0.11

0.47

-210

April 23 Bolide

Used 1D Models

Table 2.2. Predicted first arrival celerity (km/s) for

select phases: April 23, 2001 (1D)

Table 2.3. Source location and errors relative to satellite location (LO1): April 23, 2001


April 23 is59

April 23: IS59


April 23 is591

April 23: IS59


April 23 is57

April 23: IS57


April 23 is571

April 23: IS57


April 23 is53

April 23: IS53


April 23 is531

April 23: IS53


April 23 bolide1

Source

it

Lat (N)

itd

Lon (E)

isd

Origin Time (Epoch)

Lat error (deg)

Lon error (deg)

Time error (s)

IS53

0.268

0.284

0.292

LO1

27.9

-133.89

988006355

0

0

0

IS57

0.278

0.292

0.328

LA_S1

28.07

-135.09

988006347

0.17

-1.2

-8

IS59

0.284

0.3

0.311

LA_S2

27.79

-133.42

988006145

-0.11

0.47

-210

April 23 Bolide

Used 1D Models

Table 2.2. Predicted first arrival celerity (km/s) for

select phases: April 23, 2001 (1D)

Table 2.3. Source location and errors relative to satellite location (LO1): April 23, 2001


Acapulco bolide

Source

Lat (N)

Lon (E)

Origin Time (Epoch)

Lat error (deg)

Lon error (deg)

Time error (s)

it

itd

isd

LO1

14.45

-106.13

967165945

0

0

0

IS08

0.289

0.298

LA_DL1

13.68

-108.21

967166247

-0.77

-2.08

302

IS25

0.263

0.285

0.29

IS53

0.292

0.303

0.31

LA_DL2

13.37

-107.74

967165950

-1.08

-1.61

5

IS59

0.281

0.297

0.308

DLIAR

0.278

0.309

Acapulco Bolide

Table 3.2. Predicted first arrival celerity (km/s)

for select phases: August 25, 2000

Table 3.3. Source location and errors relative to satellite location (LO1): August 25, 2000


Acapulco is53

Acapulco: IS53


Acapulco is59

Acapulco: IS59


Acapulco dliar

Acapulco: DLIAR


Acapulco sa

Acapulco: SA

From A. Le Pichon, CEA/DASE: Infrasonic detections of the Acapulco bolide in South America

IS25 - French Guiana

q = 325°

IS08 - Bolivia


Acapulco bolide1

Source

Lat (N)

Lon (E)

Origin Time (Epoch)

Lat error (deg)

Lon error (deg)

Time error (s)

it

itd

isd

LO1

14.45

-106.13

967165945

0

0

0

IS08

0.289

0.298

LA_DL1

13.68

-108.21

967166247

-0.77

-2.08

302

IS25

0.263

0.285

0.29

IS53

0.292

0.303

0.31

LA_DL2

13.37

-107.74

967165950

-1.08

-1.61

5

IS59

0.281

0.297

0.308

DLIAR

0.278

0.309

Acapulco Bolide

Table 3.2. Predicted first arrival celerity (km/s)

for select phases: August 25, 2000

Table 3.3. Source location and errors relative to satellite location (LO1): August 25, 2000


Concluding remarks

Concluding Remarks

  • Stratospheric and thermospheric phases propagating in elevated ducts are invoked to explain observed celerities

  • Present limitations in location accuracy may be due to granularity of climatological models and our understanding of infrasonic scattering and diffraction in the atmosphere

  • April 23 bolide origin time best matched by results of 1D profiles

  • Acapulco bolide origin time best matched by results of 2D profiles

Benchmark events provide new tests!


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