the chelyabinsk meteor: joint interpretation of infrasound, acoustic, and seismic waves
TRANSCRIPT
International Data Centre Page 1
The Chelyabinsk meteor: joint interpretation
of infrasound, acoustic, and seismic waves
I. Kitov, D. Bobrov, and M. Rozhkov
International Data CentrePreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty OrganizationProvisional Technical SecretariatVienna International CentreP.O. Box 1200A-1400 ViennaAUSTRIA
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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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Source and energy
Ek = mV2/2 Ek = 2.35 · 1016 J
m0 = 1.3 · 107 kg 1 kt = 4.18 · 1012 J
V0 = 1.9 ·104 m/s W = 560 kt
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
Energy release history
Total energy
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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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Source and energy
V(1km) = 2500 m/s
m(1km) = 3,700 tons
Ek(1km) = 27 kt
E30 to 20 = 220 kt
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Seismic source
(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
Shock wave
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Seismic observations:
ML=2.4; (ML(REB)=2.2)
Z
ARU N
E
Z
AKTO N
E
BVAR
KURK
MKAR
REB is the Reviewed Event Bulletin, a CTBTO product available to States Parties
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Seismic observations: Pn
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Location. SSSC- Source Specific Station Corrections
Pn : 55.06 º N, 60.92º E. Ellipse: Smax=23.5 km, Smin =15.3 km
MKAR AKTO ARU
KURK BVAR
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Seismic observations: Lg
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Seismic observations:
Lg waves magnitude estimation
5 stations: ARU, AKTO, BVAR, KURK, and MKAR
Station A, nm log(A) Δ, deg 0.83*log(Δ)
Q=400, V=3.5,
f=0.5 Hz mLg
ARU 116 2.064 1.9 0.231 0.001 3.11
AKTO 39 1.591 5 0.580 0.004 2.98
BVAR 17.5 1.243 5.9 0.640 0.004 2.70
KURK 17.3 1.238 11.5 0.880 0.008 2.94
MKAR 12.2 1.086 15.8 0.995 0.012 2.90
mLg = log(A) + 0.81+ 0.83log(Δ) + γ(Δ-0.09)0.434 ; Nuttly, 1986
mLg = 2.93 ± 0.15
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Seismic observations: LR
ARU
AKTO
BVAR
KURK
AAK
OBN
MKAR
KBZ
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Seismic observations: LR
magnitude estimation
# STA Phase Delta, deg Ms Ms res
1 BVAR LR 5.22 4.21 0.25
2 ZALV LR 13.53 4.35 0.39
3 AAK LR 14.17 4.11 0.15
4 OBN LR 14.65 3.20 -0.76
5 MKAR LR 14.91 4.35 0.39
6 KVAR LR 16.05 3.91 -0.05
7 KBZ LR 16.12 4.02 0.06
8 GNI LR 18.05 3.94 -0.02
9 NRIK LR 19.33 4.07 0.11
10 AKASG LR 20.07 4.06 0.11
11 FINES LR 20.23 3.23 -0.73
12 BRTR LR 23.79 3.72 -0.24
13 MLR LR 24.47 4.18 0.22
14 HFS LR 26.33 4.02 0.07
15 NOA LR 27.41 3.96 0.00
16 VRAC LR 28.05 4.00 0.05
17 SPITS LR 28.88 3.75 -0.21
18 GERES LR 29.95 4.21 0.26
19 EIL LR 31.17 3.87 -0.09
20 DAVOX LR 33.22 4.28 0.32
21 JMIC LR 34.09 3.71 -0.24
22 BORG LR 40.55 3.91 -0.05
23 CMAR LR 45.55 3.79 -0.17
24 KSRS LR 47.21 4.23 0.27
25 BBB LR 73.81 3.87 -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 !
1. Ms(IDC) = 3.95
2. ML (REB)=2.2
3. IDC rule: no LR associated for large Ms-mb differences
4. IDC rule: no LR associated without mb
5. Ignores physics of seismic wave generation
6. Ignores historical observations from atmospheric tests
7. 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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Seismic observations, LR
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Seismic observations, LQ
NRIK
SPITS
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Atmospheric nuclear test:
seismic observations, LQ
E-W
Z
time
LQ
LR
Δ =3660 km
1 min
From: Pasechnik, I.P. (1970). Characteristic of seismic waves from nuclear explosions
and earthquakes, Nauka (in Russian)
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Location
Pn : 55.06 º N, 60.92º E, Smax=23.5, Smin=15.3
LR/LQ : 54.81º N, 62.23º E, Smax=2.5 km, Smin =1.6 km (no modelling error)
I : 53.52º N, 66.59º E, Smax=376 km, Smin=197 km
REB : 54.06º N, 61.80º E, Smax=51 km, Smin=13 km
Disintegrated
meteorite
impact zone.
Expected
trajectory:
yellow line
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Comparative SSSC-corrected Pn-location for 5 and 3 IMS station (yellow and red),
and IASPEI-based location (blue)
Lake Chebarkul
Location
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Trajectories published
by Universidad de
Antioquiahttp://urania.udea.edu.co/sitios
/facom/research/chelyabinsk-
meteoroid.php?#
Location
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Trajectory by BS2013-IAU
and YC2013-NASA, and
Universidad de Antioquia
Location
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Chulym meteorite, 1984
26.02.1984, 13:40:00
57.5º N, 85.1º E
Ek ~10 kt
mLg = 3.39
Yield = 0.33kt
(From: Ovchinnikov and Pasechnik, Meteoritika 47,1988)
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Chulym, 1984, and Chebarkul,
2013 meteorite locations
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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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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 DPRK-
2013 test:
Ru/Ra = 25.
So the yield of the air explosion which would generate such waves must be 250Kt.
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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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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
processing in the IDC. Atmospheric nuclear tests
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Thank You!