Two events crucial for monitoring of nuclear explosions under the CTBT occurred on February 12 and 15 and attracted attention of the mass media and scientists. Seismic waves from the underground event and infrasound waves from the meteorite are of extreme interest as well as various processes of energy conversion at the free surface. Infrasound station I45(RU) collocated with seismic array USRK recorded the epicentral I-phase generated by the DPRK 2013 event and the seismoacoustic wave emitted beneath the station. The shock wave from the Chebarkul meteorite generated a regular I-phase recorded by many IMS infrasound stations and a series of seismic phases likely associated with impact and acoustoseismic conversion. Due to the altitude of the peak energy release, the air-coupled ground rolls with a group velocity of 3.5 km/s were generated. A similar pattern was observed after the 1984 r.Chulym (Siberia) bolide. We estimate the energy of both sources and discuss possible mechanisms of acoustic/seismic wave generation and conversion.

1. International Data Centre Page 1
The DPRK 2013 underground test and Chebarkul meteorite:
joint interpretation of seismic, infrasound,
acoustoseismic, and seismoacoustic waves
Kitov, I., D. Bobrov, M. Rozhkov, and K. Sitnikov
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
ivan.kitov@ctbto.org

2. International Data Centre Page 2
Outline
1. The 2013 DPRK underground test
• Seismic wavefield. Cross comparison
• Seismoacoustic effect in the epicentral zone
• Local seismoacoustic wave
2. Chebarkul meteorite
• Source function
• Peak energy release. Acoustic (low-amplitude shock) wave
• Infrasound source vs. seismic source
• Acoustoseismic waves: Pn, Lg, LR, LQ
• Comparison with atmospheric nuclear tests: Love and Rayleigh
waves
• Comparison with the 1987 Chulym meteorite.

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Seismic waves: cross comparison
2013 vs. 2009 : KSRS and USRK
2009
2013
2009
2013

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Seismic waves: cross correlation relative location
Final location is based on reciprocal cross-
correlation when the estimate is based on mutual
master-slave permutation. Distance between events is
590 meters for 4 stations, and 570 meters for 22
stations. X and Y distances are 470 and 360 meters
for 4 stations, and 400 and 410 meters for 22
stations.
2009
2013
2009
2013
2006
4 regional arrays
22 IMS arrays
Joint relative location
Initial master event is DPRK-2009, primary slave is
DPRK-2013, and secondary slave is DPRK-2006 .

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DPRK 2013: LR
Ms(IDC)=3.9
USRK
KSRS
TLY
Z
H1
H2
Z
H1
H2
Z
H1
H2

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DPRK 2013: LR
Ms(IDC)=3.9
OBN
BVAR
AKTO
SPITS
LQ?
Z
H1
H2

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Epicentral seismoacoustic waves:
total energy
R
u(0)
r
u(r)
P(r) = ρCu(r)
u(r) = Ar-n
n>1
u(r) = v(R) h/R
ρ - air density
C – sound speed
u(r) – vertical velocityv(R)
v(R) = Bh-1/4 Y1/3/R
Ei/Es ~ 10-4 ; Ei – infrasound energy, Es - seismic energy
Ei ~ 10-3 kt
h
P(0)
V(R) – radial velocity; Y – yield; B - constant

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Local seismoacoustic waves
seismic vs. infrasound waveforms
Infrasound channel measures particle velocity
I45RU
USRK
USRK
I45RU

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Chebarkul meteorite: source and energy
Ek = mV2/2 Ek = 1.62 · 1016 J
m0 = 108 kg 1 kt = 4.18 · 1012 J
V0 = 1.8 ·104 m/s W = 380 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 = 0.413AΓρV3/Hvap
Luminous flux F = -(τV2/8πZ2)dm/dt
Energy release history
Total energy

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Chebarkul meteorite: 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 380kt/350km =1.1 kt/km (1.1 t/m)
Peak energy release ~6 kt/km or 200 kt in total
0
20
40
60
80
100
0 100 200 300 400 500 600 700
height,km
dV/dt, m/s·s
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8 1
height,km
ρ/ρ0
Peak light emission
Normalized Air Density Acceleration

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Chebarkul meteorite: source and energy
V(1km) = 2500 m/s
m(1km) = 3,700 tons
Ek(1km) = 27 kt
E30 to 20 = 150 kt0
20
40
60
80
100
1.E+10 1.E+11 1.E+12 1.E+13 1.E+14 1.E+15
height,km
dE/dt, J/s
0.5*V*V*dm
m*V*dV
30 km
20 km
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8 1
height,km
dE/dt
0
20
40
60
80
100
120
0100200300400
height,km
Distance, km
P
Shock wave
Normalized energy release

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Chebarkul meteorite: seismic source
h
RP2/P1
r
(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
impact
t0
t1
t2
Acousto-
seismic
source region
P2/P1Shock wave
Source shape and evolution
Nuclear test
t1-t0 ~70 sec
Δ~100 km
Shock wave

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Chebarkul meteorite: seismic observations,
Pn, ML=2.4; (ML(REB)=2.2)
Z
ARU N
E
Z
AKTO H1
H2
BVAR
KURK
MKAR

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Chebarkul meteorite: seismic observations
Pn and LgNot the impact!

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Chebarkul meteorite: seismic observations
No LR associated in the REB!
ARU
AKTO
BVAR
KURK
AAK
OBN
MKAR
KBZ

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Chebarkul meteorite: seismic observations,
LR: offline 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 stations (+ARU, AKTO,
and KURK)
Ms(IDC)max = 4.35 (ZALV
and MKAR)
Ms(IDC)min =3.20 (OBN)
Ms(IDC)ave =3.95 (±0.06)
Ms(met) > Ms(DPRK2013)
Δmax= 74º !

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Chebarkul meteorite: seismic observations,
LR
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 hypocenter 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 major gap in IDC processing at the development stage

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Chebarkul meteorite: seismic observations,
LQ
ARU
AKTO
BVAR
KURK
OBN
AAK
MKAR
KBZ

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Chebarkul meteorite: seismic observations,
LQ
NRIK
SPITS

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Atmospheric 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 km, Smin =15.3 km
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

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Chulym meteorite, 1984
26.02.1984, 13:40:00
57.5º N, 85.1º E
mLg = 3.39
Ek ~10 kt
(From: Ovchinnikov and Pasechnik, Meteoritika 47,1988)

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Local acoustoseismic wave
ARU Z
ARU N
ARU E
Station ARU: acoustoseismic wave 15 min after Pn
Δ(Pn) ~ 200 km; Δ(LR/LQ) ~ 280 km
Travel time (Pn) = 10 min
Travel time (LR/LQ) = 14 min;
No signal
Signal stronger than Lg
October 20, 1962, t0=09-21-45.6, =50.4227, =77.723, Y=6.7 kt, HOB=635 m
NCE (328 km). (By the courtesy of Sokolova I.N., IGR Kazakhstan, T2-P57)
~18 min

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Conclusions
• Infrasound signal from a relatively small underground explosion can be
measured at near-regional distances
• Local infrasound signal generated by seismic wave can be used for relative
calibration of seismic and infrasound sensors
• The energy of infrasound and seismic sources associated with a meteorite
may differ by a factor of 2
• The impact of the Chebarkul meteorite is unlikely. Debris reached the surface
• There were at least three sources different in space and time: infrasound, LR
and LQ, and Pn waves.
• These three sources are located along the trajectory
• Local acoustoseismic waves were measured at seismic station ARU
• The IDC has a major hole in joint processing of infrasound and seismic
waves from atmospheric explosions. In fact, this type of nuclear tests is
practically excluded from seismic monitoring
• The IDC misses important information on surface wave magnitude of
acoustoseismic events, which can be used for screening