ELF/VLF waves as Earthquake precursor – A case study (May 12, 2008 Wenchuan, China earthquake) Rajesh Singh, A.K. Maurya, B. Veenadhari, P. Pant 1, A.K. Singh 2 Indian Institute of Geomagnetism New Panvel, Navi Mumbai India 1 ARIES, Manora Peak, Nainital – , India 2 Physics Department, B.H.U., Varanasi – India

VTX NWC JJI 3SA ICV HWU FTA2 DHQ GBR Allahabad Nainital VNS May 12, 2008 Wenchuan China earthquake

 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 Predicting an earthquake is and has always been a challenge for Scientific Community

Seismologists Quote: ‘Earthquakes cannot be predicted’ - Geller, R.J., Jackson, D.D., Kagan, Y.Y., Mulargia, F., Science, 275, 1616, Main, I., Nature, 385, 19, 1997  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 - Friedemann, T.F. Current Science, 94, 311, 2008

 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  Anomalous behavior in Low/Ultra low electromagnetic emissions recorded all around the globe  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 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 km, different type of terminator time anomalies were found (iii) Deep (> 100 km) earthquakes did not showed any anomaly

– Hayakawa et al., 2007 Sumatra Earthquake – 26 December, 2004

– Hayakawa et al., 2007

May 12, 2008 Wenchuan, China earthquake (19th deadliest earthquake of all time) Depth: 19 kilometres (12 mi) Epicenter location: °N °E Aftershocks: 149 to 284 major & over 42,719 total Casualties: ~ 69,000 dead ~ 18,000 missing ~ 375,000 injured Magnitude: 7.9 M 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 (~ km) (Hayakawa et al., 1996; Molchanov and Hayakawa, 1998; Hayakawa 2007)

(2) Nighttime fluctuation analysis A(t) dA=A(t) -  In this method VLF amplitude corresponding Local night-time is used  Estimate Diff : dA = A(t) - A(t) is the amplitude at time ‘t’ is average over one month  Finally, integrate dA 2 over the night-time hours and have one data value for one day

Daily Amplitude Variations at NAT, ALD and VNS

Terminator -Time not visible T-T method not applicable

~5500 km Time Difference ~ 3.5 hrs Difficult to apply T-T method of analysis

Adopted the Nighttime fluctuation analysis method

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 Orbit Time ~ 4-5 UT EQ TIME: 06:28:01.42 UT

Thank you for kind attention ! These are initial observations - NOT conclusions on EQ precursors