We are conducting theoretical studies and practical validation of atm osphere/ionosphere phenomena preceding major earthquakes. Our approach is based on monitoring of two physical parameters from space: outgoi ng long-wavelength radiation (OLR) on the top of the atmosphere and e lectron and electron density variations in the ionosphere via GPS Tot al Electron Content (GPS/TEC). We retrospectively analyzed the temporal and spatial variations of OLR an GPS/TEC parameters characterizing  the state of the atmosphere and ionosphere several days before four m ajor earthquakes (M>6) in Greece for 2008-2009: M6.9 of 02.12.08, M6. 2 02.20.08; M6.4 of 06.08.08 and M6.4 of 07.01.09.We found anomalous behavior before all of these events (over land and sea) over regions o f maximum stress. We expect that our analysis reveal the underlying p hysics of pre-earthquake signals associated with some of the largest  earthquakes in Greece

Davidenko, D. A.

Kafatos, M.

Ouzounov, D. P.

Pulinets, S. A.

Taylor, P. T.

NASA Technical Reports Server

Space-borne observations of atmospheric pre-earthquake signals in 
seismically active areas. Case study for Greece 2008-2009 
 
 
Ouzounov DP1, Pulinets SA2, Davidenko DA3, Kafatos M1, Taylor PT4 
 
1CEESMO,Chapman University, Orange, CA 92866, USA, ouzounov@chapman.edu 
2Institute of Applied Geophysics, Moscow 129128, Russia 
3Space Research Institute RAS, Moscow 117997, Russia 
4NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 
 
Abstract: We are conducting theoretical studies and practical validation of 
atmosphere/ionosphere phenomena preceding major earthquakes. Our approach is based on 
monitoring of two physical parameters from space: outgoing long-wavelength radiation (OLR) on 
the top of the atmosphere and electron and electron density variations in the ionosphere via GPS 
Total Electron Content (GPS/TEC). We retrospectively analyzed the temporal and spatial 
variations of OLR an GPS/TEC parameters characterizing the state of the atmosphere and 
ionosphere several days before four major earthquakes (M>6) in Greece for 2008-2009:  M6.9 of 
02.12.08, M6.2 02.20.08; M6.4 of 06.08.08 and M6.4 of 07.01.09.We found anomalous behavior 
before all of these events (over land and sea) over regions of maximum stress. We expect that our 
analysis reveal the underlying physics of pre-earthquake signals associated with some of the 
largest earthquakes in Greece. 
 
 
1. Introduction 
The evidence for more than thirty years of data provides a large number of examples of transient 
signals preceding these earthquakes. Some of them have shown (Tronin et al., 2002; Liu et al., 
2004; Pulintes and Boyarchuk, 2004; Tramutoli et al., 2004) that studying atmospheric variability 
could also reveal active tectonic processes in the Earth’s crust. Despite the many singular reports 
showing an enhancement in the atmospheric transient fields around the time of major earthquakes 
(Ouzounov et al., 2007; Parrot, 2010, Pergola et al, 2010), there is still of a lack of coordinated 
multisensory observations shown in (Ouzounov et al., (2011a,b), which are required for an 
understanding of the complex physical processes associated with major earthquakes. 
This study explores the relationship between atmospheric processes and the occurrence of four 
major earthquakes (M>6) in Greece for 2008-2009:  M6.9 of 02.12.08, M6.2 02.20.08; M6.4 of 
06.08.08 and M6.4 of 07.01.09 by analyzing data from ground and satellite observations (Table 1, 
Figure 1).  
 
Table 1.  List of major earthquake events in Greece (2008-2009) with depths less then 50km, 
Source; University of Athens, Seismological Laboratory 
(http://www.geophysics.geol.uoa.gr/stations/maps 
https://ntrs.nasa.gov/search.jsp?R=20130011796 2019-08-31T00:31:25+00:00Z
  
Figure 1. Reference of map of Greece and location of 2008-2009 earthquakes from Table.1. Stars 
indicate epicenters; tectonic plate boundaries are in bold black, faults shown by gray lines 
 
2. Data Processing and analysis 
We have analyzed two different physical parameters characterizing the state of the atmosphere 
during the time of four earthquakes in Greece: 1. Earth outgoing long wave earth radiation (OLR) 
measured at the top of the atmosphere; and 2. Ionospheric variability of GPS, Total Electron 
Content (TEC). This approach could minimize the biased estimate of using only a singular 
parameter and provide information about the scale and physics of the changes in the atmospheric 
processes related to tectonic activity. 
 
2.1 Earth radiation observation 
OLR is one of the main parameters used to characterize the earth’s radiation environment at the 
top of the atmosphere (300mb) and includes emissions from the ground, atmosphere and clouds. 
OLR is not directly measured, but is calculated from observations using a separate algorithm. The 
National Oceanic an Atmospheric Administration (NOAA) Climate Prediction Center web site 
(http://www.cdc.noaa.gov/) provided these daily OLR data. The OLR algorithm for analyzing the 
Advanced Very High Resolution Radiometer (AVHRR) data is from Cruber and Kruger (1984) 
and integrates (Infrared) IR data between 10 and 13 microns. These data are mainly sensitive to 
near surface and/or cloud temperatures. A daily mean (by 2.5 o x 2.5 o) was used to study the main 
OLR variability in the earthquake area (Ouzounov et al., 2007, Ouzounov et al, 2011a). This has 
been proposed to be related to tectonic stresses and thermodynamic processes in the atmosphere 
and an increase in emitted radiation. The abnormal indicator, named – E-index, is defined as an 
change detection in OLR field (Ouzounov et al, 2007), indicating the presence of an anomalous 
thermal trend, similar to the RETIRA index (Tramutoli et al., 1999). The E_index represents the 
statically defined maximum change in OLR values for specific spatial locations and predefined 
times: 
  E(t) = (S*(xi, j, yi, j, t)S
*(xi, j, yi, j, t)) /i. j               (1) 
Where: t=1, K – time in days, ),,( ,,
* tyxS jiji the current OLR value and ),,( ,,
* tyxS jiji  the 
computed mean field, defined by multiple years of observations over the same location, local time 
and normalized by the standard deviation i. j (Ouzounov et al, 2007, 2011a). 
 
2.2. GPS/TEC analysis 
Analysis was made of the Athens GPS receiver, NOA1 (National Observatory of Athens), which 
for all earthquakes was inside the earthquake preparation area determined, by Dobrovolsky et al. 
(1979) or Bowman et al. (1998). The vertical TEC was calculated with a time resolution of 2 
minutes. In the second step the percentage deviation from the running mean was calculated: 
TEC =100  (TECTECav ) /TECav       (2) 
as a background level TECav the running mean was taken for 15 preceding days for every time 
moment of  UT. At the third stage the 3-D pattern of TEC was constructed where the X-axis is 
in days (7 days before earthquake and 4 after), Y-axis – UT, and Z-axis (scale bar) - TEC. We 
used the technique proposed first in Pulinets et al., (2002) 
In every figure we demonstrate the time series of the vertical TEC, standard deviation TEC, 
Percent deviation TEC and global equatorial geomagnetic Dst index. At the left panel the OLR 
anomalies are demonstrated, and at the bottom panel – the 3-D pattern of TEC. 
 
 
 
Figure 2. OLR and GPS/TEC analysis for M6.7 of 02.14.08 and M6.0 of 02.20.08 A. OLR 
anomaly from 02.17.08(07.30LT). B OLR anomaly from 02.20.02 (07.30LT). C.GPS/TEC time 
series (01.01.08-02.23.08);D. TEC map for M6.7 of 02.14.08; E. Map of 3-D pattern of TEC  
for M6.0 of 02.20.08 
 
3. Summary of Results and Conclusions  
Our OLR study includes analysis of NOAA AVHRR data between 2003 and 2009.  The OLR 
survey containing the pixels closets to the epicentral area show that the initial formation of a 
transient atmospheric anomaly was detected before the following earthquakes:  on Feb 7. 2008 (-
7 days); M6.9 of 02.12.08; (Figure 2.A); on Feb 20, 2008 (few hours in advance); M6.2 02.20.08 
(Figure 2.B); on June 8th, 2008 (few hour in advance); M6.4 of 06.08.08 (Figure 3.A); and on Jun 
11, 2009 (19 days in advance) for M6.4 of 07.01.09 (Figure 4.A). 
 
The OLR reference field was computed for each preceding month and 15 day after the event 
using all available data (2003-2009) and with a confidence level (+2/-2 sigma). All OLR 
anomalies (Figure 2.AB; Figure 3.A and Figure 4.A) show a strong transient OLR anomalous 
field (with a confident level greater than +2 sigma) near the epicentral area, over the major faults. 
The enhancement of radiative emission could be explained by the anomalous flux of the latent 
heat over the area of increased tectonic activity observed within few days before the earthquake 
(Ouzounov et al., 2007; Pulinets and Ouzounov, 2011a).  
 
Figure 3. OLR and GPS/TEC analysis for M6.4 of 08.06.08 A. OLR anomaly from 
06.08.08(07.30LT). B.GPS/TEC time series (05.15.08-06.14.08);C. Map of 3-D pattern 
of TEC  for M6.4 of 06.08.08; 
 
For the GPS/TEC analysis the most complex case was the first one  (Table 1, Figure 2) 
when two consecutive shocks M6.9 and M6.2 were observed with the time interval 6 
days (14 and 20 February 2008). That is why at the first anomalous pattern related to the 
14 Feb earthquake we are able to observe the positive deviations (pre-sunrise 0-4 AM), 
which are the precursors of the second event on 20 February (Figure 2. C, D, E) 
 
 
Figure 4. OLR and GPS/TEC analysis for M6.2 of 07.01.09 A. OLR anomaly from 
06.11.09(07.30LT). B.GPS/TEC time series (06.06.09-07.07.09);C. Map of 3-D pattern of TEC 
for M6.2 of 07.01.09; 
 
The same figures were created for two other cases of June 8, 2008 (Figure 3 C, D) and July 1, 
2009 (Figure 4 C, D). Besides the four major earthquake described in the present paper we 
analyzed five M>6 earthquakes in Greece with the same technique and created an averaged 
pattern from all 9 cases which we name the “precursor mask”.  For individual cases (like the four 
earthquakes shown in Table 1) we are able to observe sometimes only the part of this time 
interval of a different duration, shown on (Figure 2, D, E; Figure 3 C; Figure 4, C). The averaged 
pattern demonstrates that the most stable part of the precursory phenomena is the positive TEC 
deviations during the afternoon hours (from 4 PM till midnight) and a day before the earthquake 
and again positive deviations during pre-sunrise hours (0-4 AM) at the day of the quake (totally 
12 hours).  
 
4. Acknowledgements  
Authors wish to thank to Chapman University for their support, NOAA’s Climate Prediction 
Center for making OLR data available to the user community and to the National Observatory of 
Athens (NOA) for providing GPS data. 
 
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Space-borne Observations of Atmospheric Pre-Earthquake Signals in Seismically Active Areas: Case Study for Greece 2008-2009

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