Study of the electrical field Study of the electrical field related - - PowerPoint PPT Presentation

SLIDE 1

1

Study of the electrical field Study of the electrical field related to related to Kozani Kozani-

• Grevena

Grevena (Greece) Ms (Greece) Ms 6.6

6.6 earthquake of

earthquake of May 13, 1995 May 13, 1995 Preliminary results Preliminary results

Vargemezis G.

Geophysical Laboratory of Aristotle’s University of Thessaloniki, GREECE

Zlotnicki J.

CNRS-UPB-UMR6524, FRANCE

SLIDE 2

2

• Case description- Motivation
• Data collection
• Mass data processing
• Focusing in special cases
• Conclusions

SLIDE 3

3

May 13, 1995 earthquake in Kozani area, Greece

SLIDE 4

4

Model of 1995 KOZANI-GREVENA sequence

• Mw 6.6
• Strike N65oE
• Length 30km
• Width 10km
• Dip NNW
• Mean displacement

50cm

• Depth 13.6km

Papazachos et al. (1998) Papanastasiou et al. (1998)

SLIDE 5

5

Resor et al. (2005)

SLIDE 6

6

Seismicity in time

Number of events 900 Minimum 2.1 Maximum 6.6

SLIDE 7

7

SLIDE 8

8

Telluric stations

Installation EANI : 18/5/95 PANAYIA: 21/5/95 KNIDI : 28/5/95

SLIDE 9

9

Installation of KNIDI telluric station

Pb-PbCl2 Non polarized electrode 5 m Sampling interval: 4 sec

SLIDE 10

10

VOLOS remote EM station

SLIDE 11

11

• Plots of time series of raw data in different

time periods

• Filtering in different frequencies
• Time-space plots of telluric and seismic

activity

• Plots of polarization variation in time

…… Comparison with seismic activity

SLIDE 12

12

Telluric activity in KNIDI station

9 Jun 19 Jul 28 Aug 7 Oct

SLIDE 13

13

Telluric field at EANI station

20 May 30 May 9 Jun 19 Jun 29 Jun 9 Jul 19 Jul 29 Jul 8 Aug 18 Aug 28 Aug

SLIDE 14

14

Telluric field at PANAYIA station

20 May 30 May 9 Jun 19 Jun 29 Jun 9 Jul 19 Jul 29 Jul 8 Aug 18 Aug 28 Aug

SLIDE 15

15

Telluric activity in KOZANI network

20 May 30 May 9 Jun 19 Jun 29 Jun 9 Jul 19 Jul 29 Jul 8 Aug 18 Aug

140 160 180 200 220

• 300
• 200
• 100

100 PANAYIA 2 3 4 5 6 Mw

• 80
• 60
• 40
• 20

20 EANI

• 20
• 10

10 20 30 KNIDI

SLIDE 16

16

Time-Space distribution of seismic events

SLIDE 17

17

Telluric activity compared to rainfalls and seismicity

140 160 180 200 220

• 300
• 200
• 100

100 PANAYIA

• 80
• 60
• 40
• 20

20 EANI

• 20
• 10

10 20 30 KNIDI

31-May 14-Jun 28-Jun 12-Jul 26-Jul 9-Aug 23-Aug 10 20 30

Number of events

Seismicity Time Interval: 18 May-25 Aug (136-235) Knidi Knidi-Eani Eani Eani-Panayia Panayia Panayia-Knidi

10 20 30 Rainfall (mm)

SLIDE 18

18

NS V O L O S EW

TIME PERIOD: 202-235, normalized amplitude: mV/km

19-Jul 24-Jul 29-Jul 3-Aug 8-Aug 13-Aug 18-Aug 23-Aug

• 208
• 139
• 70

PAN

16 21 26

KNI

• 1

113 227

KNI

• 40
• 20

PAN

146 163 180

EW

• 50

3 56

H

• 23

22 67

D

90 145 200

NS

• 40
• 10

20

EANI

• 68
• 43
• 18

EANI

Step 1: Raw data observation

NS V O L O S EW

TIME PERIOD: 148-202, normalized amplitude: mV/km

146 153 160 167 174 181 188 195 202

127 150 173

NS

• 34

17 68

D

• 66
• 3

60

H

89 128 167

EW

• 20

20

PAN

• 20
• 15
• 10
• 5

5

KNI

• 20.0

2.0 24.0

KNI

• 300
• 200
• 100

PAN

SLIDE 19

19

Filtered data

NS V O L O S EW

TIME PERIOD: 176-202, normalized amplitude: mV/km Periods: 1<T<2h

176 181 186 191 196 201

• 53
• 7

39

PAN

• 2.0

0.1 2.2

KNI

• 3.9
• 0.2

3.5

NS

• 13
• 1

11

D

• 1.7

0.2 2.1

PAN

• 4

1 6

EW

• 0.8

0.1 1.0

KNI

• 13

2 17

H

NS V O L O S EW

TIME PERIOD: 176-202, normalized amplitude: mV/km Periods: > 4h

176 183 190 197

• 11
• 5

1

KNI

• 17
• 11
• 5

PAN

106 136 166

EW

• 45

6 57

H

• 31

15 61

D

145 154 163

NS

• 171
• 123
• 75

PAN

4 14 24

KNI

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20

Step 2: Focusing on shorter periods of data records Period A: 20 May-14 June Period B: 12 -24 July Period C: 12-27 September

SLIDE 21

21

Period A: 140-165

V O L O S

TIME PERIOD: 140-165, Band Pass (1h<T<2h)), mV/km

140 147 154 161

• 0.8
• 0.4

0.0 0.4 0.8

KNI

• 0.8

0.0 0.8

PAN

• 12

1 14

EAN

• 4

1 6

EW

• 13

2 17

H

• 4.0

0.3 4.6

NS

• 9
• 1

7

EAN

• 1.0

0.0 1.0

KNI

• 0.8
• 0.4

0.0 0.4 0.8

PAN

• 8

1 10

D

NS V O L O S EW

TIME PERIOD: 140-165, normalized amplitude: mV/km

140 142 144 146 148 150 152 154 156 158 160 162 164 166

• 121
• 61
• 1

PAN

• 20
• 3

14

KNI

124 138 152

NS

• 34

16 66

D

• 51
• 4

43

H

89 99 109 119

EW

• 2

8 18

PAN KNI

• 36
• 12

12

EANI

• 50
• 29
• 8

EANI

SLIDE 22

22

Day 143: EANI station

1

143 143.2 143.4 143.6 143.8 144 4 8 12 16

Rainfall (mm)

• 30
• 20
• 10

10 20

NS (mV/km)

• 40
• 30
• 20
• 10

EW (mV/km)

1 2 3 4 5

Mw

3.6 4.24.1 4.3 4.2

1 2 3 4 5

2 3 4 5

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23

Day 149: KNIDI station

149 149.2 149.4 149.6 149.8 150 4 8 12 16 20

Rainfall (mm)

6 6.5 7 7.5 8 8.5

NS (mV/km)

• 1.6
• 1.2
• 0.8
• 0.4

0.4

EW (mV/km)

1 2 3 4

Mw

2.9 3.2 2.6 3.2 3.3 3 2.9 3 3.6 2.8 3.2 2.9 3.53.4 3.8

Lightings

4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

. . . . . .

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

@ @ @

EANI KNIDI PANAYIA

22°5'0"E 22°5'0"E 22°0'0"E 22°0'0"E 21°55'0"E 21°55'0"E 21°50'0"E 21°50'0"E 21°45'0"E 21°45'0"E 21°40'0"E 21°40'0"E 21°35'0"E 21°35'0"E 21°30'0"E 21°30'0"E 21°25'0"E 21°25'0"E 40°15'0"N 40°15'0"N 40°10'0"N 40°10'0"N 40°5'0"N 40°5'0"N 40°0'0"N 40°0'0"N 39°55'0"N 39°55'0"N 39°50'0"N 39°50'0"N

Legend

@

T elluric Stations

Seismic Events Ms 149.0012, 2.9

2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.0195, 3.2 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.0309, 2.6 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.0882, 3.2 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.1577, 3.3 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.2425, 3 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.291, 2.9 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.3025, 3 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.3485, 3.6 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.4656, 3.2 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.5191, 2.9 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.7022, 3.5 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.7514, 3.4 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8 149.8391, 3.8 2.6 2.7 - 3.0 3.1 - 3.3 3.4 - 3.6 3.7 - 3.8

SLIDE 24

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Day 157: KNIDI station

156 156.4 156.8 157.2 157.6 158 5 10 15 20 25

Rainfall (mm)

10 10.5 11 11.5 12 12.5

NS (mV/km)

• 3
• 2
• 1

1 2

EW (mV/km)

1 2 3 4 5

Mw

3.8 3.7 4.8 2.9 3.5

4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

. . . . . .

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

@ @ @

EANI KNIDI PANAYIA

22°5'0"E 22°5'0"E 22°0'0"E 22°0'0"E 21°55'0"E 21°55'0"E 21°50'0"E 21°50'0"E 21°45'0"E 21°45'0"E 21°40'0"E 21°40'0"E 21°35'0"E 21°35'0"E 21°30'0"E 21°30'0"E 21°25'0"E 21°25'0"E 40°15'0"N 40°15'0"N 40°10'0"N 40°10'0"N 40°5'0"N 40°5'0"N 40°0'0"N 40°0'0"N 39°55'0"N 39°55'0"N 39°50'0"N 39°50'0"N

Legend

@

T elluric Stations

Seismic Events Ms 156.7728, 3.8

3.5 - 3.8 3.9 - 4.0 4.1 - 4.3 4.4 - 4.5 4.6 - 4.8

157.0325, 3.7

3.5 - 3.8 3.9 - 4.0 4.1 - 4.3 4.4 - 4.5 4.6 - 4.8

157.1917, 4.8

3.5 - 3.8 3.9 - 4.0 4.1 - 4.3 4.4 - 4.5 4.6 - 4.8

157.3764, 3.5

3.5 - 3.8 3.9 - 4.0 4.1 - 4.3 4.4 - 4.5 4.6 - 4.8

156.6 156.8 157 157.2 157.4 10.8 11 11.2 11.4 11.6 11.8

NS (mV/km)

• 2
• 1.5
• 1
• 0.5

0.5

EW (mV/km)

1 2 3 4 5

Mw

3.8 3.7 4.8 2.9 3.5

9h

1.6h

SLIDE 25

25

4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

. . . . . . . .

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

@ @ @

EANI KNIDI PANAYIA

22°5'0"E 22°5'0"E 22°0'0"E 22°0'0"E 21°55'0"E 21°55'0"E 21°50'0"E 21°50'0"E 21°45'0"E 21°45'0"E 21°40'0"E 21°40'0"E 21°35'0"E 21°35'0"E 21°30'0"E 21°30'0"E 21°25'0"E 21°25'0"E 40°15'0"N 40°15'0"N 40°10'0"N 40°10'0"N 40°5'0"N 40°5'0"N 40°0'0"N 40°0'0"N 39°55'0"N 39°55'0"N 39°50'0"N 39°50'0"N

Legend

@

T elluric Stations

Seismic Events Ms 162.0463, 2.7

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.0843, 3

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.1347, 2.7

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.2031, 3

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.2863, 2.7

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.3315, 2.9

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.3551, 2.5

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.3639, 3.2

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.3917, 2.3

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.5701, 3.4

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.6021, 2.6

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.7224, 4

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.7569, 2.9

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.786, 4.8

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.8499, 2.5

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.86, 4

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

162.8859, 3

2.3 - 3.1 3.2 - 4.0 4.1 - 4.8

Day 162: KNIDI station

162 162.2 162.4 162.6 162.8 163 4 8 12 16

Rainfall (mm)

• 12
• 10
• 8
• 6
• 4
• 2

NS (mV/km)

• 4.4
• 4
• 3.6
• 3.2
• 2.8

EW (mV/km)

1 2 3 4 5

Mw

2.7 3 2.7 3 2.7 2.9 2.9 2.5 3.2 2.4 2.3 3.4 2.6 4 2.9 4.8 2.5 4 3

SLIDE 26

26

Period B: 193-205

12 July – 24 July

SLIDE 27

27

NS V O L O S EW

TIME PERIOD: 148-202, normalized amplitude: mV/km Periods: > 4h

146 153 160 167 174 181 188 195 202

• 171
• 86
• 1

PAN

• 20

2 24

KNI

129 146 163

NS

• 32

15 62

D

• 45

6 57

H

48 107 166

EW

• 17
• 2

13

PAN

• 20
• 15
• 10
• 5

5

KNI

NS V O L O S EW

TIME PERIOD: 148-202, normalized amplitude: mV/km Periods: 1<T<2h

146 153 160 167 174 181 188 195 202

• 2

2

PAN

• 0.8

0.1 1.0

KNI

• 4

1 6

EW

• 12

12

D

• 4.0

0.3 4.6

NS

• 13

2 17

H

• 2.0

0.1 2.2

KNI

• 53
• 6

41

PAN

Filtered data

SLIDE 28

28

Daily plot: Day 193

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

2.8 2.8 2.8 2.6 2.4 2.4

1 2 3

6 8 10

KNIDI

1 2 3

PANAYIA EANI

KOZANI Julian Day: 193 (12/7/95)

Telluric stations Epicenters-Magnitudes EW component NS component Polarity

VOLOS

SLIDE 29

29

Daily plot: Day 194

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

3.2 2.5 2.1

1 2 3 4

4 8 12

KNIDI PANAYIA

1 2 3 4

EANI

KOZANI Julian Day: 194 (13/7/95)

Telluric stations Epicenters-Magnitudes EW component NS component Polarity

VOLOS

SLIDE 30

30

Filtered data: 194-205

V O L O S

TIME PERIOD: 194-205, Band Pass (1h<T<2h), mV/km

194 198 202

• 53
• 13

27

PAN

• 0.5

1.5

KNI

• 3
• 1

1

EAN

• 5

5

NS

• 12

12

D

• 12

2 16

H

• 5

5

EW

• 14

3 20

EAN

• 2

2

PAN KNI

1 2 3 4 5 6

M

13-Jul 14-Jul 15-Jul 16-Jul 17-Jul 18-Jul 19-Jul 20-Jul 21-Jul 22-Jul 23-Jul

194.5 195.5 196.5 197.5 198.5 199.5 200.5 201.5 202.5 203.5

10 20 30

Number of events

1 7 9 24 3 6 4 2 3

Seismicity Time Interval: 13 July-23 July (194-204) Knidi Knidi-Eani Eani Eani-Panayia Panayia Panayia-Knidi

SLIDE 31

31

Period: 196-199 JD

V O L O S

TIME PERIOD: 196-199, Periods: 1-2h, mV/km

196 197 198 199 200

PAN PAN KNI KNI EW H

• 13
• 8
• 3

D NS

2 4 6 Mw

V O L O S

TIME PERIOD: 196-199, Raw data, mV/km

196 197 198 199 200

• 294
• 194
• 94

PAN PAN

• 3
• 1

KNI

9 13 17 21

KNI

• 40
• 10

20

EAN

• 68
• 43
• 18

EAN

122 132 142 152

EW

• 67
• 4

59

H

• 33
• 13

7 27 47

D

132

NS

2 4 6 Mw

SLIDE 32

32

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

2.4

KNIDI

9.6 10.0 10.4 10.8 11.2

1 2 3 1 2 3

PANAYIA EANI

KOZANI Julian Day: 196 (15/7/95)

Telluric stations Epicenters-Magnitudes EW component NS component Polarity

VOLOS

SLIDE 33

33

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

2.9 2.9 2.7 2.6 2.5 2.5 2.5 2.4 2.3 2.2 2.2 2 2 1.9

1 2 3

• 4
• 3
• 2
• 1

9 10 11

KNIDI

1 2 3

PANAYIA EANI

KOZANI Julian Day: 197 (16/7/95)

Telluric stations Epicenters-Magnitudes EW component NS component Polarity

VOLOS

SLIDE 34

34

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

5 3.3 3.1 3 2.8 2.6 2.5 2.3 2 2

1 2 3 4 5

• 2.0
• 1.0

0.0 9.0 9.5 10.0 10.5 11.0

KNIDI

1 2 3 4 5

PANAYIA EANI

KOZANI Julian Day: 198 (17/7/95)

Telluric stations Epicenters-Magnitudes Major fault EW component NS component Polarity

VOLOS

SLIDE 35

35

21.3 21.4 21.5 21.6 21.7 21.8 21.9 22.0 39.9 40.0 40.1 40.2 40.3 40.4

4.2 3.8 3.8 3.3 3.2 3.1 3.1 3.1 3 2.9 2.8 2.8 2.7 2.7 2.7 2.6 2.6 2.6 2.6 2.5 2.5 2.5 2.5 2.5 2.4 2.4 2.4 2.4 2.4 2.2 2.2 2.2 2.1 2 2 1.9

1 2 3 4 5

• 1.2
• 0.4

0.4 8 12 16 20 24

KNIDI

• 300
• 250
• 200
• 150
• 100
• 50

1 2 3 4 5

PANAYIA EANI

KOZANI Julian Day: 199 (18/7/95)

Telluric stations Epicenters-Magnitudes EW component NS component Polarity

VOLOS

SLIDE 36

36

Pre-seismic electric signal?

197.2 197.6 198 198.4 198.8

• 4

4 8 12 mV/km 2 4 6 Mw

KNIDI NS EW Seismicity

SLIDE 37

37

Period C: 255-275 (12-27 Sep)

SLIDE 38

38

Period C: 255-275 (12-27 Sep)

4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

. . . . . . . . .

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

@ @ @

EANI KNIDI PANAYIA

22°0'0"E 22°0'0"E 21°55'0"E 21°55'0"E 21°50'0"E 21°50'0"E 21°45'0"E 21°45'0"E 21°40'0"E 21°40'0"E 21°35'0"E 21°35'0"E 21°30'0"E 21°30'0"E 21°25'0"E 21°25'0"E 21°20'0"E 21°20'0"E 21°15'0"E 21°15'0"E 40°25'0"N 40°25'0"N 40°20'0"N 40°20'0"N 40°15'0"N 40°15'0"N 40°10'0"N 40°10'0"N 40°5'0"N 40°5'0"N 40°0'0"N 40°0'0"N

Legend

2.1

12-Sep 13-Sep 14-Sep 15-Sep 16-Sep 17-Sep 18-Sep 19-Sep 20-Sep 21-Sep 22-Sep 23-Sep 24-Sep 25-Sep 26-Sep 27-Sep

1 2 3

M

SLIDE 39

39

Raw data

V O L O S

TIME PERIOD: 255-275, Raw Data, mV/km

256 260 264 268 272

• 220
• 200
• 180
• 160
• 140

K N I

66 94 122

N S

• 22

50 122

D

• 131
• 45

41

H

167 189 211

E W

172 176 180 184

K N I

V O L O S

TIME PERIOD: 255-275, Periods 1-2h, mV/km

256 260 264 268 272

• 20
• 10

10 20

K N I

• 12
• 8
• 4

4 8

N S

• 20
• 10

10 20

D

• 30
• 20
• 10

10 20 30

H

• 8
• 4

4 8

E W

• 1

1

K N I

SLIDE 40

40

256 260 264 268 272 5 10 15 20 25 Rainfall (mm)

• 220
• 200
• 180
• 160
• 140

KNIDI 172 174 176 178 180 182 184

EW (mV/km)

13-Sep 17-Sep 21-Sep 25-Sep 29-Sep

1 2 3

M

SLIDE 41

41

Time varying polarization

SLIDE 42

42

SLIDE 43

43

SLIDE 44

44

KNIDI PANAYIA EANI

SLIDE 45

45

KNIDI EANI PANAYIA JULIAN DAYS

SLIDE 46

46

CONCLUSION

• Polarization of the electric field over the electric

network is strongly inhomogeneous, depending

• n the location of the station relatively to the

location and the mechanism of the active fault

• Electric field varies strongly very close to the

epicentral area

• Electrical anomalies are transient effects with

amplitude of a few mV/km

• Abnormal changes of the telluric field sometimes

are mostly related with rainfalls (need of local data for every station)

SLIDE 47

47

To be done…..

• Filtering in higher frequencies (up to

0.25Hz)

• Cross correlation of different data sets
• Discrimination of proseismic/coseismic or

postseismic signals

• Study of the origin of anomalous signals
• Pattern recognition of probable

seismoelectric signals