VLF sub-ionospheric signals and Earthquake precursor signatures? Results from the studies of some recent Earthquakes Ajeet K Maurya, Rajesh Singh, B. Veenadhari Indian Institute of Geomagnetism New Panvel, Navi Mumbai – , India The Sharjah-Stanford AWESOME VLF Workshop Feb 22-24, 2010

Earthquakes: Facts and Nomenclature EQ- Magnitude CategoryNumber(/Year)Energy Released ( J/yr) ≥ 8.0Great EQ0-10-1, Major EQ Strong EQ Moderate EQ1, Light EQ13, Minor EQ> 100, Source: Ionospheric Precursor of EQ, Springer

 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 Earthquake prediction: A Challenge for Scientific community

 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?

Lithosphere-atmosphere-Ionosphere Coupling – Types Electromagnetic Coupling: Connected with the direct penetration of DC electric field induced due to the appearance of Seismic-related electric charges on the Earth’s surface. It can lead to substantial modifications of ionospheric properties. Chemical Coupling: Determined by the variation of the fair weather electric field in the lower ionosphere due to the enhancement of conductivity of lower atmospheric layer ionized by radon emanating from Seismic faults. Dynamic Coupling: Implies influence of atmospheric wave processes originating near the Earth surface on the lower ionosphere.

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 behavior, 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)

Ionospheric Precursors: For different ionospheric layers F-Layer: Critical frequency of F layer (f o F 2 ) E-Layer: Critical frequency of Sporadic E-Layer (f o E s ) D-Layer : Phase and Amplitude of ELF/VLF signals from navigational transmitters Out of these three types lot of work have been done by Japanese and Russian group on D-region precursors studies. ( Pulinets et al 1991, Lipervosky et al 2000, Hayakawa 1996, Gokhberg et al., 1982; Gufeld et al., 1992 )

Precursory Effects in D-layer : Use of VLF signals  VLF waves are emerges as one of the most reliable and important method for continuous D-region monitoring.  The amplitude and phase distortion of the received VLF Navigational transmitter signal were interpreted as influence of the Earth-Ionosphere Waveguide where the VLF signals propagates.  This distortion is due to ionospheric lowering over the region of the Earth-quake preparation.  By the method of triangulation it is possible to determine the position of future epicenter and form the distortion amplitude to determine the EQ magnitude.

Earthquake Preparation Zone  The area on the ground surface where precursory phenomenon associated with the approaching Earthquake are observed. It is also called the activation zone  The radius of preparation zone is given as : Km Where ρ=radius of preparation zone, M= Earthquake magnitude (Dobrovolsky et al 1979)

Primarily two methods of analysis is proposed using sub-ionospheric VLF data to make out precursory effects of ionospheric perturbations  Terminator time method  Night time fluctuation method

(1) Terminator Time Method (Hayakawa et al., 1996; Molchanov and Hayakawa, 1998; Hayakawa 2007)  Abnormal behavior occurs around the sunrise & sunset of local times.  Effective on E-W meridian plane propagation direction and Short paths (~ km)  Evening Terminator is more indicative of Seismic influence  Generally an increase in the evening terminator and decrease in morning terminator time.

Kobe Earthquake (7.3 M) in 1995 (depth=20km)  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  Sift for Evening T-T is ~45 min.  Distance between receiver and transmitter is ~1000km

(2) Nighttime fluctuation analysis  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. Use full for large distance (d>1000km) (Shvets et al., 2004a, b; Roznoi et al., 2004; Maekawa at al., 2006)

– Hayakawa et al., 2007 Sumatra Earthquake – 26 December, 2004 M=9.0 depth=30km

– Hayakawa et al., 2007

Recent Earthquake Observations

Facts about propagation paths JJI and Allahabad: Distance ~4800 km Time difference: ~3:30 hrs Direction form Allahabad ~ East NWC and Allahabad: Distance ~ 6300 km Time difference: ~ 2:30 hrs Direction form Allahabad ~ South-East

China Earthquake: Special Case May 12, 2008 Wenchuan Magnitude: 7.9 M Epicenter location: °N °E Depth: 19 km (12 mi) Aftershocks: 149 to 284 major & over 42,719 total TIME: 06:28:01.42 UT

T-T Method is not applicable  Time diference~3.5hrs Difficult to apply T-T method

Adopted the Nighttime fluctuation analysis method

NWC Earthquake

Details of selected Earthquake Date: 02-Sep-09, Location: Java, Indonesia Lat: 7.809S, E Magnitude: 7.0, Depth: 46.2Km Time: at epicenter, 07:55:01UT Radius of Preparation Zone: Km Date: 30-Sep-09, Location: Southern Sumatra, Indonesia Lat: 0.725S, E Magnitude: 7.5, Depth: 81Km Time: at epicenter, 10:16:09UT Radius of Preparation Zone:1678.8Km Date: 01-Oct-09, Location: Southern Sumatra, Indonesia Lat: 2.508S, E Magnitude: 6.6, Depth: 15Km Time: at epicenter, 01:52:28UT Radius of Preparation Zone: Km Date: 10-Aug-09, Location: Andaman Islands, India Lat: N, E Magnitude: 7.5, Depth: 33.1Km Time: at epicenter, 19:55:39UT Radius of Preparation Zone:1678.8Km

Methodology: T-T Method of analysis 10-Aug-EQ (Magnitude: 7.5, Depth: 33.1Km) Change in Evening Terminator Time: ~11minute

Methodology: T-T Method of analysis Methodology: T-T Method of analysis 30-Sep & 1-Oct-EQ (Magnitude: 7.5, 6.6 Depth: 81Km, 15km) Shift in Evening Terminator Time: ~20minute

Methodology: T-T Method of analysis 02-Sep-EQ (Magnitude: 7.0, Depth: 46.2Km) Shift in Evening Terminator Time: ~22minute

Methodology: Night time Fluctuation Method of analysis 10-Aug-EQ (Magnitude: 7.5, Depth: 33.1Km) Lowest

Methodology: Night time Fluctuation Method of analysis 30-Sep & 1-Oct-EQ (Magnitude: 7.5, 6.6 Depth: 81Km, 15km) Lowest

Methodology: Night time Fluctuation Method of analysis 02-Sep-EQ (Magnitude: 7.0, Depth: 46.2Km) Lowest

JJI-Earthquake Date: 28-Aug-09, Location: Northern Qinghai, China Lat: N, E Magnitude: 6.2, Depth: 13Km Time: at epicenter, 01:52:06UT Radius of Preparation Zone: Km Date: 21-Sep-09 Location: Bhutan, Lat: N, Long:91.412E Magnitude: 6.1, Depth: 14Km Time: at epicenter, 08:53:06 UT Radius of Preparation Zone: Km

Both method of analysis have been applied: T-T Method of Analysis No Change in Terminator Time

Night time Fluctuation Analysis It shows the lowest value of fluctuation amplitude on the day of EQ compared the days around the EQ days. Lowest It shows the lowest value of fluctuation amplitude two days before the EQ day.

 So, we clearly see the increase in the VLF amplitude fluctuation for 12 May, 2008 China Earthquake  This is not true for all the Earthquakes  Subject of Seismic-Ionospheric perturbations caused by Earthquakes needs more attention and study  In case of Andaman and Indonesian we see lowest values of fluctuation on EQ day - with increase before and after EQ  Clear shift in Evening Terminator time ~ 10 – 25 min for Andaman and Indonesian EQ is seen Summary No Uniform Pattern is Observed

Thank you for your kind attention