- Peak energy release. Acoustic (low-amplitude shock) wave - Infrasound source vs. seismic source - Seismic waves: Pn, Lg - Acousto-seismic waves: LR, LQ - Comparison with atmospheric nuclear tests: Love and Rayleigh waves - Comparison with the 1987 Chulym meteorite

1. The Chelyabinsk meteor: joint interpretation
of infrasound, acoustic, and seismic waves
I. Kitov, D. Bobrov, and M. Rozhkov
International Data Centre
Preparatory Commission for the Comprehensive
Nuclear-Test-Ban Treaty Organization
Provisional Technical Secretariat
Vienna International Centre
P.O. Box 1200
A-1400 Vienna
AUSTRIA
Mikhail.Rozhkov@ctbto.org
International Data Centre
Page 1

2. Outline
•
Sources of signals
•
Peak energy release. Acoustic (low-amplitude shock) wave
•
Infrasound source vs. seismic source
•
Seismic waves: Pn, Lg
•
Acousto-seismic waves: LR, LQ
•
Comparison with atmospheric nuclear tests: Love and Rayleigh
waves
•
Comparison with the 1987 Chulym meteorite
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3. Source and energy
Total energy
Ek = mV2/2
m0 = 1.3 · 107 kg
V0 = 1.9 ·104 m/s
Ek = 2.35 · 1016 J
1 kt = 4.18 · 1012 J
W = 560 kt
Energy release history
Dynamic traction
Pdyn = ρ(h)CDV2
Aerodynamic deceleration
dV/dt = - ρ CDV2 /m(t)
Dissipation of kinetic energy
dE = 0.5V2dm + mVdV
Ablation
dm/dt = AρV3
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4. Source and energy
Flight time ~20 s; Flight distance ~350 km
Flight height change ~90 km
Height of peak light emission ~ between 30 km and 20 km
Duration of peak emission ~ 3 s
Length of peak emission ~ 35 km
Average energy release per km 560kt/350km =1.5 kt/km (1.5 t/m)
Peak energy release
~9 kt/km or 300 kt in total
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5. Source and energy
V(1km) = 2500 m/s
m(1km) = 3,700 tons
Ek(1km) = 27 kt
E30 to 20
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= 220 kt
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6. Seismic source
Shock wave
(P2-P1)/P1 < 0.1 (high altitude explosion)
P1 - surface atmospheric pressure; P 2 – shock wave pressure
ΔP(r,t)/P1 = (ΔP(R0)/P1 )max(1-ta/L+)exp(-ta/L+)
ΔP = P2-P1 ; R0 – radius of peak overpressure; t – time;
a – sound speed near the surface; L+ - the length of shock wave
Source shape and evolution
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7. Seismic observations:
ML=2.4; (ML(REB)=2.2)
REB is the Reviewed Event Bulletin, a CTBTO product available to States Parties
Z
ARU N
E
Z
AKTO N
E
BVAR
KURK
MKAR
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8. Seismic observations: Pn
International Data Centre
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9. Location. SSSC- Source Specific Station Corrections
Pn : 55.06 º N, 60.92º E. Ellipse: Smax=23.5 km, Smin =15.3 km
AKTO
MKAR
KURK
International Data Centre
ARU
BVAR
Page 9

10. Seismic observations: Lg
International Data Centre
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11. Seismic observations:
Lg waves magnitude estimation
5 stations: ARU, AKTO, BVAR, KURK, and MKAR
mLg = log(A) + 0.81+ 0.83log(Δ) + γ(Δ-0.09)0.434 ; Nuttly, 1986
Station
ARU
AKTO
BVAR
KURK
MKAR
A, nm
116
39
17.5
17.3
12.2
log(A)
2.064
1.591
1.243
1.238
1.086
Δ, deg 0.83*log(Δ)
1.9
0.231
5
0.580
5.9
0.640
11.5
0.880
15.8
0.995
Q=400, V=3.5,
f=0.5 Hz
0.001
0.004
0.004
0.008
0.012
mLg
3.11
2.98
2.70
2.94
2.90
mLg = 2.93 ± 0.15
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12. Seismic observations: LR
ARU
AKTO
BVAR
KURK
AAK
OBN
MKAR
KBZ
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13. Seismic observations: LR
magnitude estimation
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
STA
BVAR
ZALV
AAK
OBN
MKAR
KVAR
KBZ
GNI
NRIK
AKASG
FINES
BRTR
MLR
HFS
NOA
VRAC
SPITS
GERES
EIL
DAVOX
JMIC
BORG
CMAR
KSRS
BBB
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Phase
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
LR
Delta, deg
5.22
13.53
14.17
14.65
14.91
16.05
16.12
18.05
19.33
20.07
20.23
23.79
24.47
26.33
27.41
28.05
28.88
29.95
31.17
33.22
34.09
40.55
45.55
47.21
73.81
Ms
4.21
4.35
4.11
3.20
4.35
3.91
4.02
3.94
4.07
4.06
3.23
3.72
4.18
4.02
3.96
4.00
3.75
4.21
3.87
4.28
3.71
3.91
3.79
4.23
3.87
Ms res
0.25
0.39
0.15
-0.76
0.39
-0.05
0.06
-0.02
0.11
0.11
-0.73
-0.24
0.22
0.07
0.00
0.05
-0.21
0.26
-0.09
0.32
-0.24
-0.05
-0.17
0.27
-0.09
25 IMS stations
(also detected at ARU,
AKTO, and KURK)
Ms(IDC) = 3.95 ± 0.06
Ms(IDC)max = 4.35 (ZALV
and MKAR)
Ms(IDC)min =3.20 (OBN)
Ms > Ms(DPRK2013)=3.9
Δmax= 74º !
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14. Seismic observations, LR
1.
2.
3.
4.
5.
6.
7.
Ms(IDC) = 3.95
ML (REB)=2.2
IDC rule: no LR associated for large Ms-mb differences
IDC rule: no LR associated without mb
Ignores physics of seismic wave generation
Ignores historical observations from atmospheric tests
What CTBT monitoring misses?
• Accurate epicenter location of atmospheric tests
with LR azimuths and travel times
• Altitude estimate from periods of LR and LQ
• Size estimate from amplitudes and periods
• Fusion of seismic and infrasound wavefield
• Interpretation of the event nature (nuclear tests vs. meteorites)
A serious gap in IDC processing at the development stage
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15. Seismic observations, LQ
NRIK
SPITS
International Data Centre
Page 15

16. Atmospheric nuclear test:
seismic observations, LQ
Δ =3660 km
time
LR
Z
1 min
LQ
E-W
From: Pasechnik, I.P. (1970). Characteristic of seismic waves from nuclear explosions
and earthquakes, Nauka (in Russian)
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17. Location
Pn
LR/LQ
I
REB
:
:
:
:
55.06 º N, 60.92º E, Smax=23.5, Smin=15.3
54.81º N, 62.23º E, Smax=2.5 km, Smin =1.6 km (no modelling error)
53.52º N, 66.59º E, Smax=376 km, Smin=197 km
54.06º N, 61.80º E, Smax=51 km, Smin=13 km
Disintegrated
meteorite
impact zone.
Expected
trajectory:
yellow line
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18. Location
Comparative SSSC-corrected Pn-location for 5
and 3 IMS station (yellow and red),
and IASPEI-based location (blue)
Lake Chebarkul
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19. Location
Trajectories published
by Universidad de
Antioquia
http://urania.udea.edu.co/sitios
/facom/research/chelyabinskmeteoroid.php?#
International Data Centre
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20. Location
Trajectory by BS2013-IAU
and YC2013-NASA, and
Universidad de Antioquia
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21. Chulym meteorite, 1984
(From: Ovchinnikov and Pasechnik, Meteoritika 47,1988)
26.02.1984, 13:40:00
57.5º N, 85.1º E
Ek ~10 kt
mLg = 3.39
Yield = 0.33kt
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22. Chulym, 1984, and Chebarkul,
2013 meteorite locations
International Data Centre
Page 22

23. Comparing Chulym, 1984, Chebarkul, 2013, and
DPRK 2013 nuclear test
Mag
Chulym
Chebarkul
Effect from
ML
Not measured
2.4
Hitting the ground
MLg
3.31
2.93
Hitting the ground
Ms
Not measured
3.95
Shock wave
What could we say about Chebarkul event if we would have only seismic observations?
“UNE case”:
• UNE manifestations at regional seismic stations: Pn, Lg and LR waves.
• Pn and LR locations give different coordinates and can’t be associated as a single source.
Comparing ML with the one determined by IDC from the DPRK-2013 event
(ML(IDC)=4.5).
• The DPRK-2013 yield was around 10kt.
• The explosion yield is proportional to the signal amplitude measured when estimating a
magnitude.
• From the magnitude measurements we can see that the Cheb is almost 100 times smaller
(2 magnitude units).
• The approximate yield of the explosion generating same body waves as Cheb is 0.1 kt.
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24. Comparing Chulym, 1984, Chebarkul, 2013, and
DPRK 2013 nuclear test
Mag
Chulym
Chebarkul
Effect from
ML
Not measured
2.4
Hitting the ground
MLg
3.31
2.93
Hitting the ground
Ms
Not measured
3.95
Shock wave
If Cheb were an atmospheric nuke.
• ATM test phenomena: prominent surface waves (Rayleigh and Love waves).
• UNE: a ratio R of energy transmitted to LR waves to total explosion energy is:
RUNE=ELR/EUNE = 10-6
RAIR= 4*10-8 for Air Nuclear Test
DPRK-2013: Ms = 3.9
• Cheb event Ms = 3.95
DPRK-2013 was an underground explosion, Cheb was an air explosion, so the
equivalent yield of this meteor explosion must be 25 times higher than the DPRK2013 test:
Ru/Ra = 25.
So the yield of the air explosion which would generate such waves must be 250Kt.
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Page 24

25. Comparing Chulym, 1984, Chebarkul, 2013, and
DPRK 2013 nuclear test
MLg discussion
• We estimated MLg=2.9 for Chebarkul event.
• To generate waves with such magnitude, UNE with the yield Y=0.2 kt must be conducted
(according to Nuttly magnitude scale).
• Though the numbers for Pn and Lg magnitudes are different (0.1kt and 0.2kt), the yields
estimated according to these magnitudes are really close taking into account uncertainties
of M to Y conversion for Lg based measurements.
• Estimation of a kinetic energy corresponding to such explosion gives the mass of the
space body which has hit the ground between 1 and 100 t (the range is due to uncertain
meteor velocity and some other parameters).
• Different mechanisms of wave generation (Pn and LR) in Cheb and Chul cases produce
difference in energy release as respectively 1/2 and 50:
 MLg1 – MLg2 = 3.31 – 2.93 (2.99 by Ovchinnikov) = 0.38 which corresponds
approx. to yield ratio of 2.5 (2).
 The meteorite energy estimated by us as ~500kt. Ovchinnikov and Pasechnik (1988)
estimated Chulym meteor yield as 10 kT, so the shock wave energy ratio for these
two events is 50.
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26. Conclusions
• The energy of infrasound and seismic sources
associated with a meteorite may differ by a factor
of 2.
• Just a small part of the meteorite hit the surface
as debris.
• There were at least three sources separated in
space and time: (1) infrasound, (2) LR and LQ,
and (3) Pn, Sn, and Lg waves.
• These three sources are located along the
meteorite trajectory.
• There is a major hole in automatic and interactive
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27. Thank You!
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Page 27