1. Tectonics or magma intrusion?
-- new results from multi-parameter study
at Gede Volcano, West Java, Indonesia
D Hidayat1, H Gunawan2, M Hendrasto2, A Basuki2, F Schwandner1, S Marcial1, S
Kunrat2
1
Earth Observatory of Singapore, Nanyang Technological University
2
Center for Volcanology and Geological Hazard Mitigation, Indonesia

2. Gede Volcano,
West Java,
Indonesia
JAKARTA
Danau
BOGOR Jatiluhur
Pangrango
©2009 Google – Map Data ©2009 and Europa Technologies

3. Eruptive history of Gede
Seismic behavior
at Gede

4. Monitoring Scheme Initial no of station: 2 (1-component)
Currently: 9 stations (3 components:
For Gede & Salak Volcanoes BB and short period)
Planned: 1 CO2 flux monitoring
PUN

5. Example of data Drumplot during normal period
Drumplot during swarm

6. Locatable VT at and around Gede Volcano May 2011– Aug 2012
no report

7. Gede Hypocenters May 2011 – 26 Feb 2012

8. ede Hypocenters during swarm 27 Feb- 9 Apr 2012

9. Gede Hypocenters Aug 2012

10. Receiver function study reveals
2 low velocity zones under Gede

11. Gede Hypocenters during swarm vs Results from Receiver Function Study

12. Comparison with previous swarm
Hypocenters of 1997 swarm Hypocenters of 2012 swarm

13. Tilt time-series
Deformation monitoring by
tiltmeters Jun-Jul 2011
Tilt vector

14. Tilt time-series
Deformation monitoring by
tiltmeters (Nov 2011-Feb 2012)
Tilt vector 11/2011 – 26/02/2012

15. Tilt time-series
Deformation monitoring by
tiltmeters (27 Feb ’12-Jun ‘12)
Tilt vector

16. Tilt time-series
Deformation monitoring by
tiltmeters (Aug-Sep 2012)
Tilt vector

17. Flank CO2 flux measurement campaigns
Highlight: 2011 NE sector: higher CO2 activity
2011-2012 flank CO2 flux :
•Campaigns:
• May, Sept 2011 (n 134)
• March 2012 (n 40)
•Method:
• high resolution CO2
accumulation chamber
(LICOR Li8100A)
• ~10 points/day, >3/site
•Results [CO2 g/m2/d]:
• 019.8 mean (2011)
112.5 max (2011)
• 011.7 mean (2012)
043.4 max (2012)
Compare flanks Gede -Merapi
mean ~40, max ~120 g/m2/day
(9/2002 at Woro)
Toutain et al. 2002, Figs.1,8

18. Possible source causing the earthquakes:
-tectonic related earthquakes (faulting)
-DVT (distal VT)

19. Concluding Remarks
-Prior to the swarm in Feb-Mar 2012 and Aug 2012, sequences of
small earthquakes occurred along NE-SW across Gede and
Pangrango.
-A short VT swarms occurred 27 Feb-8 Mar 2012. We postulates
that there may be a magma intrusion under Gede volcano but do
not lead to any eruption. Similar swarms occurred in 1997 were
located under Gede Volcano.
-Tilt data suggest deformation is controlled by local tectonic until
early Nov 2011. Then tilt vector change suggests inflation due to
(possibly) magma intrusion, followed by swarm of earthquakes at the
end of Feb 2012. Several months later tilt data is back to NE
direction. While CO2 flux measurements around Gede suggest some
high flux around NE from the volcano.
-Gede & Salak activity need to be continously monitored with multi-
parameter stations as any larger swarm, deformation, or gas flux
changes may lead to surface activity (eruption) which will affect
people living around the volcano.

20. Thank you