Oceanic T-waves are earthquake signals that originate when elastic waves interact with the fluid–elastic interface at the ocean bottom and are converted to acoustic waves in the ocean. These waves propagate long distances in the Sound Fixing and Ranging (SOFAR) channel and tend to be the largest observed arrivals from seismic events. Thus, an understanding of their generation is important for event detection, localization, and source-type discrimination. Recently benchmarked seismic self-starting fields are used to generate elastic parabolic equation solutions that demonstrate generation and propagation of oceanic T-waves in range-dependent underwater acoustic environments. Both downward sloping and abyssal ocean range-dependent environments are considered, and results demonstrate conversion of elastic waves into water-borne oceanic T-waves. Examples demonstrating long-range broadband T-wave propagation in range-dependent environments are shown. These results confirm that elastic parabolic equation solutions are valuable for characterization of the relationships between T-wave propagation and variations in range-dependent bathymetry or elastic material parameters, as well as for modeling T-wave receptions at hydrophone arrays or coastal receiving stations.

1.
E. A.
Okal
, “
The generation of T waves by earthquakes
,” in
Advances in Geophysics
, edited by
R.
Dmowska
(
Academic
,
San Diego
,
2008
), Vol.
49
, pp.
1
65
.
2.
J.
Guilbert
,
J.
Vergoz
,
E.
Schisselé
,
A.
Roueff
, and
Y.
Cansi
, “
Use of hydroacoustic and seismic arrays to observe rupture propagation and source extent of the mw = 9.0 Sumatra earthquake
,”
Geo. Res. Lett.
32
,
L15310
(
2005
).
3.
J.
Talandier
and
E. A.
Okal
, “
Monochromatic T waves from underwater volcanoes in the Pacific Ocean: Ringing witnesses to geyser processes?
,”
Bull. Seis. Soc. Am.
86
,
1529
1544
(
1996
).
4.
J. H.
Haxel
and
R. P.
Dziak
, “
Evidence of explosive seafloor volcanic activity from the Walvis Ridge, South Atlantic Ocean
,”
Geo. Res. Lett.
32
,
L13609
(
2005
).
5.
D.
Reymond
,
O.
Hyvernaud
,
J.
Talandier
, and
E. A.
Okal
, “
T-wave detection of two underwater explosions off Hawaii on 13 April 2000
,”
Bull. Seis. Soc. Am.
93
,
804
816
(
2003
).
6.
R. P.
Dziak
,
D. R.
Bohnenstiehl
,
H.
Matsumoto
,
C. G.
Fox
,
D. K.
Smith
,
M.
Tolstoy
,
T.-K.
Lau
,
J. H.
Haxel
, and
M. J.
Fowler
, “
P- and T-wave detection thresholds, Pn velocity estimate, and detection of lower mantle and core P-waves on ocean sound-channel hydrophones at the Mid-Atlantic Ridge
,”
Bull. Seis. Soc. Am.
94
,
665
677
(
2004
).
7.
J.
Talandier
and
E. A.
Okal
, “
On the mechanism of conversion of seismic waves to and from T waves in the vicinity of island shores
,”
Bull. Seis. Soc. Am.
88
,
621
632
(
1998
).
8.
N. R.
Chapman
and
R.
Marrett
, “
The directionality of acoustic T-phase signals from small magnitude submarine earthquakes
,”
J. Acoust. Soc. Am.
119
,
3669
3675
(
2006
).
9.
R. P.
Dziak
, “
Empirical relationship of T-wave energy and fault parameters of northeast Pacific Ocean earthquakes
,”
Geo. Res. Lett.
28
,
2537
2540
(
2001
).
10.
E. A.
Okal
, “
T-phase stations for the international monitoring system of the comprehensive nuclear-test ban treaty: A global perspective
,”
Seis. Res. Lett.
72
,
186
196
(
2001
).
11.
E. A.
Okal
,
P.
Alsset
,
O.
Hyvernaud
, and
F.
Schindelé
, “
The deficient T waves of tsunami earthquakes
,”
Geophys. J. Int.
152
,
416
432
(
2003
).
12.
C. D.
de Groot-Hedlin
and
J. A.
Orcutt
, “
Excitation of T-phases by seafloor scattering
,”
J. Acoust. Soc. Am.
109
,
1944
1954
(
2001
).
13.
P.-F.
Piserchia
,
J.
Virieux
,
D.
Rodrigues
,
S.
Gaffet
, and
J.
Talandier
, “
Hybrid numerical modelling of T-wave propagation: Application to the Midplate experiment
,”
Geophys. J. Int.
133
,
789
800
(
1998
).
14.
J. L.
Stephens
,
G. E.
Baker
,
R. W.
Cook
,
G.
D'Spain
,
L. P.
Berger
, and
S. M.
Day
, “
Empirical and numerical modeling of T-phase propagation from ocean to land
,”
Pure Appl. Geophys.
158
,
531
565
(
2001
).
15.
Y.
Cansi
and
N.
Bethoux
, “
T waves with long inland paths: Synthetic seismograms
,”
J. Geophys. Res.
90
,
5459
5465
, doi: (
1985
).
16.
Z.
Upton
,
M. D.
Collins
, and
J.
Pulli
, “
Hydroacoustic blockage prediction and measurement at Diego Garcia using the Adiabatic Mode Parabolic Equation Model
,”
J. Acoust. Soc. Am.
123
,
3942
(
2008
).
17.
S. D.
Frank
,
R. I.
Odom
, and
J. M.
Collis
, “
Elastic parabolic equation solutions for underwater acoustic problems using seismic sources
,”
J. Acoust. Soc. Am.
133
,
1358
1367
(
2013
).
18.
J. M.
Collis
,
W. L.
Siegmann
,
F. B.
Jensen
,
M.
Zampolli
,
E. T.
Küsel
, and
M. D.
Collins
, “
Parabolic equation solution of seismo-acoustics problems involving variations in bathymetry and sediment thickness
,”
J. Acoust. Soc. Am.
123
,
51
55
(
2008
).
19.
M.
Park
,
R. I.
Odom
, and
D. J.
Soukup
, “
Modal scattering: A key to understanding oceanic T-waves
,”
Geo. Res. Lett.
28
,
3401
3404
(
2001
).
20.
W.
Jerzak
,
W. L.
Siegmann
, and
M. D.
Collins
, “
Modeling Rayleigh and Stoneley waves and other interface and boundary effects with the parabolic equation
,”
J. Acoust. Soc. Am.
117
,
3497
3503
(
2005
).
21.
H.
Kolsky
,
Stress Waves in Solids
(
Dover
,
New York
,
1963
), p.
8
.
22.
M. D.
Collins
, “
Higher-order Padé approximations for accurate and stable elastic parabolic equations with application to interface wave propagation
,”
J. Acoust. Soc. Am.
89
,
1050
1057
(
1991
).
23.
J. D.
Schneiderwind
,
J. M.
Collis
, and
H. J.
Simpson
, “
Elastic Pekeris waveguide normal mode solution comparisons against laboratory data
,”
J. Acoust. Soc. Am.
132
,
EL182
EL188
(
2012
).
24.
W. M.
Ewing
,
W. S.
Jardetzky
, and
F.
Press
,
Elastic Waves in Layered Media
(
McGraw-Hill
,
New York
,
1957
), p.
8
.
25.
M. D.
Collins
, “
A higher-order parabolic equation for wave propagation in an ocean overlying an elastic bottom
,”
J. Acoust. Soc. Am.
86
,
1459
1464
(
1989
).
26.
D. A.
Outing
,
W. L.
Siegmann
,
M. D.
Collins
, and
E. K.
Westwood
, “
Generalization of the rotated parabolic equation to variable slopes
,”
J. Acoust. Soc. Am.
120
,
3534
3538
(
2006
).
27.
E. T.
Küsel
,
W. L.
Siegmann
, and
M. D.
Collins
, “
A single-scattering correction for large contrasts in elastic layers
,”
J. Acoust. Soc. Am.
121
,
808
813
(
2007
).
28.
M. D.
Collins
, “
The rotated parabolic equation and sloping ocean bottoms
,”
J. Acoust. Soc. Am.
87
,
1035
1037
(
1990
).
29.
M. D.
Collins
,
J. P.
Lingevitch
, and
W. L.
Siegmann
, “
Wave propagation in poro-acoustic media
,”
Wave Motion
25
,
265
272
(
1997
).
30.
B. A.
McCollom
and
J. M.
Collis
, “
Root finding in the complex plane for seismo-acoustic propagation scenarios with Green's function solutions
,”
J. Acoust. Soc. Am.
136
,
1036
1045
(
2014
).
31.
L.
Tolstoy
and
W. M.
Ewing
, “
The T phase of shallow-focus earthquakes
,”
Bull. Seis. Soc. Am.
40
,
25
52
(
1950
).
32.
F. B.
Jensen
,
W. A.
Kuperman
,
M. B.
Porter
, and
H.
Schmidt
, “
Computational Ocean Acoustics
,” in
Modern Acoustics and Signal Processing
, 2nd ed., edited by
R. T.
Beyer
(
Springer
,
New York
,
2011
), pp.
86
88
, 358.
33.
R. H.
Johnson
and
R. A.
Norris
, “
T-phase radiators in the Western Aleutians
,”
Bull. Seis. Soc. Am.
58
,
1
10
(
1968
).
34.
P. D.
Slack
,
C. G.
Fox
, and
R. P.
Dziak
, “
P wave detection thresholds, Pn velocity estimates, and T wave location uncertainty from oceanic hydrophones
,”
J. Geophys. Res.
104
,
13061
13072
, doi: (
1999
).
35.
D. A.
Walker
,
C. S.
McCreery
, and
Y.
Hiyoshi
, “
T-phase spectra, seismic moments, and tsunamigenesis
,”
Bull. Seis. Soc. Am.
82
,
1275
1305
(
1992
).
36.
Y.
Yang
and
D. W.
Forsyth
, “
Improving epicentral and magnitude estimation of earthquakes from t phases by considering the excitation function
,”
Bull. Seis. Soc. Am.
93
,
2106
2122
(
2003
).
37.
J. D.
Milliman
,
Z.
Jiezao
,
L.
Anchun
, and
J. I.
Ewing
, “
Late Quaternary sedimentation on the Outer and Middle New Jersey Continental Shelf: Result of two local deglaciations?
,”
J. Geol.
98
,
966
976
(
1990
).
38.
R.
Butler
, “
Observations of polarized seismoacoustic T waves at and beneath the seafloor in the abyssal Pacific ocean
,”
J. Acoust. Soc. Am.
120
,
3599
3606
(
2006
).
39.
R. A.
Stephen
,
S. T.
Bolmer
,
M. A.
Dzieciuch
,
P. F.
Worcester
,
R. K.
Andrew
,
L. J.
Buck
,
J. A.
Mercer
,
J. A.
Colosi
, and
B. M.
Howe
, “
Deep seafloor arrivals: An unexplained set of arrivals in long-range ocean acoustic propagation
,”
J. Acoust. Soc. Am.
126
,
599
606
(
2009
).
40.
R.
Butler
and
C.
Lomnitz
, “
Coupled seismoacoustic modes on the seafloor
,”
Geo. Res. Lett.
29
,
1418
1422
(
2002
).
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