1. Triggered Earthquakes at Koyna, India
IASPEI 2009, Cape Town, South Africa
National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad, India
- Harsh Gupta, D.Shashidhar, K.Mallika, N.Purnachandra Rao, D.Nagesh, HVS.Satyanarayana, S.Saha, RT.Babu Naik and VP.Dimri

2. Globally, there are over 100 Artificial Water Reservoir sites where triggered earthquakes have occurred
Majority of the sites where triggered earthquakes of M ≥ 5 occurred are in SCR

3. KOYNA SITE
Most damaging RTS, event of December 10, 1967
Continued RTS since 1962
M ≥ 5 earthquakes: 1967, 1968, 1973, 1980, , 2000, 2005
Common Characteristics
Nucleation
Pore Fluid Pressure

4. Seismicity of the Koyna Region

5. Energy Released in Koyna region:
The Max. Credible Earthquake (MCE) considered for Koyna: M = 6.8
Empirical relation used: Log E = 1.5 M , (M = magnitude)
Using the above relation EMCE = 1022
Energy released so far:
Case 1:
E = 1 x EM x EM x EM 4.5
= 10(21.25) + 10(20.5) + 10(18.55) =
Percentage of MCE = / = 87 %
Case 2:
E = 1 x EM x EM x EM4.3
= 10(21.25) + 10(19.75) + 10(18.25) =
Percentage of MCE = / = 32 %
Considering the average of the above 2 extreme cases,
About 50% of energy may be released in Koyna

6. Real time monitoring at Koyna since August 2005.

7. At Koyna Reservoir
After several years as early as August 17,2005, a peak water level of m at koyna was reached
Fastest loading rate ever:
to m in just 55 days at Koyna.
Kaiser effect is observable

8. At Warna Reservoir
From a level of m on 23rd June 2005, it has risen to 626.9m on 15th August 2005.
This has been the fastest loading when the water level rose by 32.84m in just 53 days.

9. An Earthquake of M~5 may occur at Koyna
Kaiser effect was observable at both the reservoirs.
An enhanced seismic activity during August,2005 was observed and a M 4.2 earthquake occurred on 14th August 2005.
Two clusters were also identified nearer to Warna reservoir.
Based on the above factors a forecast was made on 25th August 2005 that ‘an earthquake of M~5 may occur at Koyna region in the weeks to follow’.
“And this forecast has come true with an earthquake of M 4.8 on 30th August 2005, Origin Time:08:53:18.1 (UTC), with location oN, oE and depth is 6.9km”
-CURRENT SCIENCE, VOL 89, 10TH SEP 2005, Gupta et. al.

10. Precursory Seismicity patterns

11. Total no of events in a area of 10km radius: 21
30 August 2005:
Earthquake of M 4.8
Nucleation time: 110 hrs
Total no of events in a area of 10km radius: 21
Largest being M 2.1
50 hrs Preceding Nucleation only 2 events

12. Total no of events in a area of 10km radius: 27
13 November 2005:
Earthquake of M 4.0
Nucleation time: 160 hrs
Total no of events in a area of 10km radius: 27
Largest being M 3.0
50 hrs Preceding Nucleation only 3 events

13. Total no of events in a area of 10km radius: 30
26 December 2005:
Earthquake of M 4.2
Nucleation time: 150 hrs
Total no of events in a area of 10km radius: 30
Largest being M 2.9
50 hrs Preceding Nucleation only 6 events

14. 17 April 2006: Earthquake of M 4.7 Nucleation time: 380 hrs
Total no of events in a area of 10km radius: 50
Largest being M 2.7
50 hrs Preceding Nucleation only 2 events

15. Events preceding the Main shock during the Nucleation time
Main earthquake
Duration of Nucleation Period (hours)
No. of events before the Main earthquake M M M
Largest earthquake
50 hrs prior to beginning of nucleation period
30 August 2005
M 4.8
110 13 8
2.6 2
13 November 2005 M 4.0
160 18 1
3.0 3
26 December M 4.2
150 22
2.9 6
17 April 2006
M 4.7
380 40 10
2.7

16. Forecast of an M~4 earthquake in the Koyna region
16th May 2006 at 7pm, IST
“On the basis of the data available from 7 seismic stations operating in the Koyna region, we have identified a nucleation, which started on 12th May, This may lead to the occurrence of an M~4 earthquake in the next 15 days. This shallow earthquake ( focal depth < 8 km ) will occur within a radius of 10 km centered at 17.10N, 73.80E. On the basis of our previous experience of studying nucleation-preceding earthquakes in the Koyna region, we expect this earthquake to occur over the next 15 days time (till 31st May, 2006), with a 50% probability.”
-JOUR.GEOL.SOC.INDIA, VOL.68, JULY2006, Gupta et. al.

17. Nucleation Preceding an M 4.2 Earthquake
Successfully Forecasted
Event observing Nucleation
Earthquake of M 4.2 in Zone-A
occurred on 21st May 2006
at 20:29:01.2 UTC.
The epicenter of this earthquake ( N, E),
lies within 10 km of the
predicted epicenter.
The focal depth is 4.7 km.
Nucleation time lasted for 250 hrs

18. Forecast of M 3.4 EQ Occurred on 14th Oct 2007
2007, October
2007, October 8 – 25
Successful
Forecast of M 3.4 EQ
Occurred on 14th Oct 2007

19. Forecast of M 3.0 EQ Occurred on 2nd July 2008
2008, June 13 – 4 July
2008, June
Successful
Forecast of M 3.0 EQ
Occurred on 2nd July 2008

20. Three Zones of Seismic Activity in the Koyna Region

21. A New Zone Of Seismic Activity
March 2007
Kandwan

22. Conclusions
Triggered earthquakes have continued to occur in the Koyna region for over 4 decades now.
The seismic activity being localized, with no other seismic activity in the vicinity, makes Koyna an ideal location for studying earthquake precursors.
We have found that earthquakes of M~4 are generally preceded by a nucleation lasting 100 to 400 hours before the main shock.
Proper monitoring makes it possible to make short term forecasts.
However, even in a small region like Koyna, we find that currently from among the three active areas, precursory nucleation is observed in only one area.
We have also discovered a new zone of seismic activity in Koyna for the past two years which gets activated in the months of February/March. This is possibly due to creation of another small reservoir which gets filled up seasonally.

23. Thank you

24. Earthquakes of M ≥ 3.5 in Zone - A
S.No
Day of
occurrence
Origin Time
(h m s)
Latitude
(oN)
Longitude
(oE)
Depth
(km)
Magnitude
(ML)
Remarks 1
17.161
73.793
5.0
4.2 - 2
17.147
73.780
6.8
4.8 3
17.134
73.783
4.0
Common nucleation,
being only one week
apart 4
17.209
73.765
5.9
4.1 5
17.149
73.786
5.8 6
17.145
73.785
3.9
4.7 7
17.171
73.777 8
17.143
2.5
3.8 9
73.784
3.6
4.3 10
17.136
73.789
After shock of # 9 11
17.139
73.778
4.4
3.5

25. Earthquakes of M ≥ 3.5 in Zone - B
S.No
Date of
occurrence
Origin Time
(h m s)
Latitude
(oN)
Longitude
(oE)
Depth
(km)
Magnitude
(ML) 1
17.111
73.705
3.1
4.8 2
17.107
73.710
3.3
4.6 3
17.108
73.711
2.1
4.1 4
17.102
2.8
3.5 5
17.109
73.704
3.6

26. Earthquakes of M ≥ 3.5 in Zone - C
S.No
Date of
occurrence
Origin Time
( h m s )
Latitude
(oN)
Longitude
(oE)
Depth
(km)
Magnitude
(ML) 1
17.334
73.755
11.4
3.5 2
17.339
73.766
5.7 3
17.281
73.728
2.1
3.8 4
17.324
73.747
3.2
4.3 5
17.297
73.771
7.8
4.8

27. Non-nucleation Phase at Zone - B
Earthquakes of M~4 in Zone-B occurred on 24 November 2007.
Aftershocks followed after the Main earthquakes in a tight cluster.

28. Non-nucleation Phase at Zone - C
Earthquake of M 4.8 in Zone-C occurred on 16 September 2008.
Absence of foreshock activity near epicentral region is clearly visible.

29. Zones Bearing Nucleation/Non-nucleation for Moderate Earthquakes in the Koyna Region
Zone A
Zone B
Zone C
Nucleation
preceded
not preceded
M 3.5 – 3.9 2 3
M 4.0 – 4.4 5 1
M 4.5 – 4.9 -

30. Successful forecasts in the Koyna Region
On the basis of clean nucleation pattern:
Successful forecasts in the Koyna Region

31. Reservoir Water Levels (2005, 2006)

32. Reservoir Water Levels (2007-2008)

33. Seismicity levels of the Koyna-Warna area (Aug’05-9July’06)
Seismicity map Histogram