1. Eruptive cycles inferred from ground deformation at Piton de La Fournaise
- A case study for the GlobVolcano project -
A. Peltier1, E. Kaminski2, JC. Komorowski1
with contributions from T. Staudacher, M. Bianchi
1. Equipe de Géologie des systèmes volcaniques, Institut de Physique du Globe de Paris (IPGP), France
2. Equipe de Dynamique des fluides géologiques, IPGP

2. Geological Setting N Piton de La Fournaise
Introduction GPS data PSInSAR Conclusion
Geological Setting
130
150
170
190 N 70
Indian Ocean 60 50 40
Piton de La Fournaise 30 20
(Gauss Laborde Réunion Coordinates, km)

3. Number of eruptions per year
Introduction GPS data PSInSAR Conclusion 1 2 3 4 5
Number of eruptions per year
Eruptive Activity
130
150
170
190
rest
rest N 70
1920
1930
1940
1950
1960
1970
1980
1990
2000 60 50
2 eruptions per year 40
Piton de La Fournaise
Rest Periods : , 30
Since 1998 : 26 eruptions 20
(Gauss Laborde Réunion Coordinates, km)

4. Elevation of eruptive fissures
Introduction GPS data PSInSAR Conclusion
Eruptive fissures : N
Distal eruptions
Elevation of eruptive fissures
Proximal eruptions
Summit eruptions
(Peltier et al., in press, JVGR)
Proximal eruption
Distal eruption
Summit eruption
1000
2000
Elevation (m)
01-jan-00
01-jan-02
01-jan-04
01-jan-06
Eruptive cycles

5. Continuous GPS network
Introduction GPS data PSInSAR Conclusion
Deformation network
Tiltmeter network N
Extensometer network
Dolomieu
Bory
Continuous GPS network
(since 2004)

6. Piton Bien car bcp d’éruption et permet
Introduction GPS data PSInSAR Conclusion
Piton de La Fournaise: 
High eruptive activity
Well monitored with ground deformation network
 Good case study for the GlobVolcano project
Projet GlobVolcano
Piton Bien car bcp d’éruption et permet
De valider les données avec les field data

7. Piton Bien car bcp d’éruption et permet
Introduction GPS data PSInSAR Conclusion
Piton de La Fournaise: 
High eruptive activity
Well monitored with ground deformation network
 Validation of deformation mapping products
Projet GlobVolcano
Piton Bien car bcp d’éruption et permet
De valider les données avec les field data

8. GPS data (2004-2007) Introduction - GPS data - PSInSAR - Conclusion
NS component
EW component
(Peltier, 2007)

9. Short-term eruptive displacements
Introduction GPS data PSInSAR Conclusion
GPS data ( )
Short-term eruptive displacements
(up to 20×103 mm d-1)
NS component
EW component
(Peltier, 2007)

10. Short-term eruptive displacements
Introduction GPS data PSInSAR Conclusion
GPS data ( )
Short-term eruptive displacements
(up to 20×103 mm d-1)
(1)
(2)
(1)
Horizontal displacements
Vertical displacements
(2)
Horizontal displacements
Vertical displacements
NS component
EW component
(Peltier, 2007)

11. Short-term eruptive displacements
Introduction GPS data PSInSAR Conclusion
GPS data ( )
Short-term eruptive displacements
(up to 20×103 mm d-1)
(1)
(1)
ΔP = 2.2 MPa
Explained data: 89%
NS component
EW component
(Peltier et al. 2008, EPSL)

12. Short-term eruptive displacements
Introduction GPS data PSInSAR Conclusion
GPS data ( )
Short-term eruptive displacements
(up to 20×103 mm d-1)
(1)
NS component
EW component
(Peltier et al. in press, JVGR)

13. Pre-eruptive long term inflation
Introduction GPS data PSInSAR Conclusion
GPS data ( )
Pre-eruptive long term inflation
( mm d-1)
NS component
EW component
(Peltier et al. in press, JVGR)

14. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
GPS ↔ available data for the PSInSAR product validation.
(M. Bianchi)

15. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
GPS ↔ available data for the PSInSAR product validation.
1st stage: identify time periods with a continuous GPS record.
(M. Bianchi)

16. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
GPS ↔ available data for the PSInSAR product validation.
1st stage: identify time periods with a continuous GPS record.
5 GPS stations with a continuous record between April 2004 and March 2007:
- 3 at the summit BORg, DSRg, SNEg
- 2 reference stations, outside of the summit cone.
SNEg
BORg
DSRg
(M. Bianchi)

17. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
GPS ↔ available data for the PSInSAR product validation.
1st stage: identify time periods with a continuous GPS record.
5 GPS stations with a continuous record between April 2004 and March 2007:
- 3 at the summit BORg, DSRg, SNEg
- 2 reference stations, outside of the summit cone.
(M. Bianchi)

18. GPS positions over S2 PS results (2004-2007)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
GPS ↔ available data for the PSInSAR product validation.
1st stage: identify time periods with a continuous GPS record.
5 GPS stations with a continuous record between April 2004 and March 2007:
- 3 at the summit BORg, DSRg, SNEg
- 2 reference stations, outside of the summit cone.
GPS positions over S2 PS results ( )
(M. Bianchi)

19. January 2004 distal eruption
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
BORg station
January 2004 distal eruption
(M. Bianchi)

20. PS time series, DSRg station
Introduction GPS data PSInSAR Conclusion
PS time series, DSRg station

21. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
To avoid the lack of coherency between images used to compute the interferograms, we focused on the pre-eruptive unrest periods.
2nd stage : find the longest time period with no eruption disturbing both the GPS and the PSInSAR records.
the selected period ranges between March and October 2005.
Two distinct deformation phases can be identified : (1) from March to July
(2) from July to October

22. Validation of deformation mapping products (PSInSAR)
Introduction GPS data PSInSAR Conclusion
Validation of deformation mapping products (PSInSAR)
To avoid the lack of coherency between images used to compute the interferograms, we focused on the pre-eruptive unrest periods.
2nd stage : find the longest time period with no eruption disturbing both the GPS and the PSInSAR records.
the selected period ranges between March and October 2005.
Two distinct deformation phases can be identified : (1) from March to July
(2) from July to October
Estimates of displacement rates in the line of sight of the satellite as inferred from the PSInSAR time series.
Estimates of GPS displacement rates in the line of sight of the satellite as inferred from the PSInSAR time series.

23. Comparison between PSInSAR and GPS data
Introduction GPS data PSInSAR Conclusion
Comparison between PSInSAR and GPS data
Good agreement between the two methods, within their associated error bars

24. Comparison between PSInSAR and GPS data
Introduction GPS data PSInSAR Conclusion
Comparison between PSInSAR and GPS data
Good agreement between the two methods, within their associated error bars

25. Conclusion – Ground deformation mapping product
Introduction GPS data PSInSAR Conclusion
Conclusion – Ground deformation mapping product
GPS data : Two time scales of ground deformation
(1) Large short-term ground displacements (up to 20×103 mm d-1), a few min to hours prior each eruption
(2) Small long-term ground displacements during pre-eruptive unrest ( mm d-1 of summit inflation)
For the pre-eruptive unrest periods :
Good agreement between the PSInSAR and GPS data : PSInSAR data provide global inference of the ground deformation field
PSInSAR data : useful complementary information for accurate ground displacement mapping

26. PSInSAR at Piton de La Fournaise Complementary to GPS data
Introduction GPS data PSInSAR Conclusion
Perspectives
PSInSAR at Piton de La Fournaise
Complementary to GPS data
GPS data: dynamics of the ground deformation in real-time
PSInSAR data: cover a larger area
Dolomieu
Bory

27. PSInSAR at Piton de La Fournaise Complementary to GPS data
Introduction GPS data PSInSAR Conclusion
Perspectives
Distal eruptions
PSInSAR at Piton de La Fournaise
Complementary to GPS data
Notably for the distal eruptions located outside of the summit cone where no field monitored networks are implemented
Dolomieu
Bory

28. PSInSAR at Piton de La Fournaise
Introduction GPS data PSInSAR Conclusion
Perspectives
Distal eruptions
PSInSAR at Piton de La Fournaise
Support to early stage warning of volcanic risk especially during distal eruptions.
Dolomieu
Bory

29. Ground deformation mapping
Introduction GPS data PSInSAR Conclusion
Product Validation at Piton de La Fournaise
Ground deformation mapping
Surface thermal anomalies

30. Results of the validation
Introduction GPS data PSInSAR Conclusion
Other product validation : Surface thermal anomalies (ASTER-SPOT-MODIS)
Results of the validation
September January 2007 eruption
GlobVolcano mass flux is about 30% larger than the volumetric flux measured by the observatory.
This implies an average porosity of about 30% for the lava flow, which agrees with both literature reference and some measurements made by the observatory.

31. Introduction - GPS data - PSInSAR - Conclusion
Other product validation : Surface thermal anomalies (ASTER-SPOT-MODIS)
Increase of surface activity linked with the summit crater collapse: flux estimated at > 50m3/s on the field
MODIS MIR- saturation
(B. Hirn)

32. Introduction - GPS data - PSInSAR - Conclusion
Other product validation : Surface thermal anomalies (ASTER-SPOT-MODIS)

33. Piton Bien car bcp d’éruption et permet
Introduction GPS data PSInSAR Conclusion
Product validation at Piton de La Fournaise: 
Ground deformation mapping
Surface thermal anomalies
Remarkable agreement found between ground data and GlobVolcano product.
- Both the location of the eruptive center, the emplacement of active lava flow, the ground displacements and the eruptive mass flux appear as robust and as accurate as the observatory record.
Projet GlobVolcano
Piton Bien car bcp d’éruption et permet
De valider les données avec les field data

34. THANKS for your attention !!!