ELF/VLF waves as Earthquake precursor
– A case study
(May 12, 2008 Wenchuan, China earthquake)
Rajesh Singh, A.K. Maurya, B. Veenadhari, P. Pant1, A.K. Singh2
Indian Institute of Geomagnetism
New Panvel, Navi Mumbai - 410218 India
Manora Peak, Nainital – 263129, India
2Physics Department, B.H.U. , Varanasi – 221005 India
1ARIES,
GBR DHQ
FTA2
HWU ICV
Nainital
3SA
Allahabad
VNS
VTX
May 12, 2008 Wenchuan
China earthquake
NWC
JJI
Predicting an earthquake is and has always been
a challenge for Scientific Community
 People who live in a seismically active region of the
world would like to know when an earthquake will occur
 But Earthquake are notorious for striking suddenly.
 They cause death and devastation apparently without
warning
 Tens of thousand of lives and damage to the
structures and infrastructures could be saved, if early
warning are available
Seismologists Quote:
‘Earthquakes cannot be predicted’
- Geller, R.J., Jackson, D.D., Kagan, Y.Y., Mulargia, F., Science, 275, 1616, 1997
- Main, I., Nature, 385, 19, 1997
- Friedemann, T.F. Current Science, 94, 311, 2008
 This statement is true if the only tools for prediction are those of
Siesmology and Geodesy: Earthquakes can indeed not be predicted
 Because what ever the probability models for prediction available in
seismology are based on past seismograph data and geological records
 The data that goes into these models are retrospective: The
knowledge acquired over the past events is used to forecast future
events –
Statistical Analysis
 So, even the most elaborate models is inadequate because it is not
based on information that might become available in real time about a
specific earthquake that looms ahead

In last couple of decades scientific community is trying to
investigate problem of earthquake prediction by looking into:
(i) Are there other signals that rock produce when subjected to ever
increasing stress?
(ii) If such signals are produced at depth, can they be transmitted or
somehow carried from the seismogenic region to region of the
earth?
Prospective pre-earthquake signals
 Local magnetic field variations over a wide range of timescales
 Enhanced infrared emissions from the epicentral region
 Change in the atmosphere near the ground and at altitudes up to ~ 1000 m
 Unusual animal behaviour, etc
 Perturbations in the lower ionosphere above the epicentral region
 Anomalous behavior in Low/Ultra low electromagnetic emissions recorded
all around the globe
The scientific community has been deeply divided over these signals
and whether or not they are indeed pre-earthquake indicators
(Henderson et al., JGR, 1993; Rodger et al, Radio Sci., 1999 and others)
VLF/LF radio sounding
Search for Seismo-ionospheric perturbations:
Previous Works
 First attempt was done by Russian workers (Gokhberg et al.,
1982; Gufeld et al., 1992). They studied long VLF path form
Reunion Omega transmitter to Omsk and Moscow, looking for
any earthquake effect in the Caucasia region – Found anomaly
for Spitak earthquake
Kobe Earthquake (7.3 M) in 1995
 Reported significant shift in the terminator times before the
earthquake, inferring daytime felt by VLF signal is elongated for a
few days around the earthquake.
– Hayakawa et al., 1996
 Later a much more extensive study by Molchanov and
Hayakawa, 1998 based on much more events during 13
years for same propagation path Tushima to Inubo came to
following conclusions:
(i) For shallow earthquakes (depth < 30 km), terminator time
anomaly was found similar to Kobe earthquake
(ii) When the depth is in medium range of 30-100 km, different
type of terminator time anomalies were found
(iii) Deep (> 100 km) earthquakes did not showed any anomaly
Sumatra Earthquake – 26 December, 2004
– Hayakawa et al., 2007
– Hayakawa et al., 2007
May 12, 2008 Wenchuan, China earthquake
(19th deadliest earthquake of all time)
Magnitude: 7.9 M
Epicenter location:
31.021°N 103.367°E
Depth: 19 kilometres (12 mi)
Aftershocks: 149 to 284 major
& over 42,719 total
Casualties: ~ 69,000 dead
~ 18,000 missing
~ 375,000 injured
TIME: 06:28:01.42 UT
Tested all the proposed method of analysis
Primarily two methods of analysis is proposed using sub-ionospheric
VLF data to make out precursory effects of ionospheric perturbations
(1) Terminator Time Method
 Effective on E-W meridian plane propagation direction and
Short paths (~ 1000-2000 km)
(Hayakawa et al., 1996; Molchanov and Hayakawa, 1998; Hayakawa 2007)
(2) Nighttime fluctuation analysis
 In this method VLF amplitude
corresponding Local night-time is
used
 Finally, integrate dA2 over the
night-time hours and have one data
value for one day
<A>
<A>
6
4
Amplitude(a.u.)
 Estimate Diff : dA = A(t) - <A>
A(t) is the amplitude at time ‘t’
<A> is average over one month
8
A(t)
A(t)
2
0
dA=A(t) - <A>
dA=A(t)-<A>
-2
-4
0
2
4
6
8
10
12
14
IST(Hours)
16
18
20
22
24
Daily Amplitude Variations at NAT, ALD and VNS
JJI-Nainital: Daily Amplitude Variation
JJI-Varanasi: Daily Amplitude Variation
JJI-Allahabad: Daily Amplitude Variation
20-May
20-May
16-May
EQ-12-May
11-May
EQ-12-May
EQ-12-May
11-May
11-May
29-April
21-April
20-April
20-April
0
2
4
6
8
10
12
14
Time in LT
16
18
20
22
24
0
2
4
6
8
10
12
14
Time in LT
16
18
20
22
24
0
2
4
6
8
10
12
14
Time in LT
16
18
20
22
24
JJI-Allahabad: Daily Amplitude Variation
16-May
EQ-12-May
11-May
29-April
Terminator -Time not visible
T-T method not
applicable
20-April
0
2
4
6
8
10
12
14
Time in LT
16
18
20
22
24
~5500 km
Time Difference ~ 3.5 hrs
Difficult to apply T-T method of analysis
Adopted the Nighttime fluctuation analysis method
JJI-VNS: Daily Night Time Amlitude Variation
JJI-NAT: Daily Night Time Amlitude Variation
JJI-VNS: Daily Night Time Amlitude Variation
20-May
20-May
16-May
EQ-12-May
EQ-12-May
EQ-12-May
11-May
11-May
11-May
20-April
12
20-April
20-April
14
16
18
Time in UT
20
22
24
12
14
16
18
Time in UT
20
22
24
12
14
16
18
Time in UT
20
22
24
JJI-ALD: Night Fluctuations
JJI-VNS: Night Fluctuations
1200
9000
Q
Fluctuation (a.u.)
M
ay
600
400
200
7000
ay
2-
800
M
-1
6000
5000
4000
3000
2000
1000
0
-M
20
ay
ay
il
pr
-A
19
-M
16
il
pr
-A
20
0
JJI-NAT: Night Fluctuations
10000
EQ
ay
M
2-1
8000
Fluctuation (a.u.)
Fluctuation (a.u.)
2-1
EQ
8000
E
1000
6000
4000
2000
-M
20
ay
il
pr
-A
20
0
Kp < 4
 So ionospheric perturbation due to solar activity can be ruled out
DEMETER Q-look ELF Spectrum
06 May 2008
Orbit: 20545_0
07 May 2008
Orbit: 20560_0
08 May 2008
Orbit: 20575_0
09 May 2008
Orbit: 20589_0
10 May 2008
Orbit: 20604_0
11 May 2008
Orbit: 20619_0
E-quake
12 May 2008
Orbit: 20633_0
13 May 2008
Orbit: 20648_0
EQ TIME: 06:28:01.42 UT
Orbit Time ~ 4-5 UT
These are initial observations
- NOT conclusions on EQ precursors
Thank you for kind attention !