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Small-scale deformation associated with the summit eruption of Kīlauea Volcano, Hawai‘i, from TerraSAR-X Interferometry
1 Friedrich-Schiller-University Jena Grietgasse 6, Jena Germany, D-07743 [email protected]
2 Hawaiian Volcano Observatory 51 Crater Rim Drive, Hawaii National Park USA - HI, 96718-0051 [email protected]
3 Jet Propulsion Laboratory 4800 Oak Grove Drive, Pasadena USA – CA, 91109 [email protected]
Nicole Richter1, Michael P. Poland2, Paul R. Lundgren3
Cont
act
Hawaiian Volcanoes: From Source to Surface AGU Chapman Conference
Waikoloa, Hawaii, USA | 20 - 24 August 2012
1 km
H
Summiteruptivevent
W155˚ 30' W155˚ 00'
N19˚ 30'
W155˚ 20' W155˚ 10' W154˚ 50'
N19˚ 20'
N19˚ 10'
SWRZ
ERZ
SummitCaldera
N 10 kmPuʻu ʻŌʻōCrater
HAWAI‘I ISLAND
Halema’uma’u Crater (H)St
udy
Area
& In
tens
ion
Dat
a &
Met
hods
Resu
lts
Fig. 2: Example of improvement in using the (B) high resolution LIDAR DEM: (A) Interferogram (2009/01/19-2009/04/17) processed using the SRTM 30 m
DEM. (C) Resulting interferogram (3 m spatial resolution). Right column: Zoom-in of the Halema'uma'u Crater.
On 19 March 2008, a new eruptive vent formed along the east wall of Halema‘uma‘u Crater at the summit of Kīlauea Volcano, Hawai‘i.
The ongoing summit eruption is characterized by degassing, seismic activity with varying frequencies (including very-long period), and the presence of an active lava lake within the vent at a level ranging from 60-200 m below the floor of Halema‘uma‘u Crater.
Over time, the vent has grown in diameter sporadically since its formation due to collapses of the unstable vent rim or conduit wall. These collapses are typically accompanied by seismicity and a dusty plume of debris and volcanic gas and often result in the deposition of ejecta on the rim of Halema’uma’u Crater—a significant local hazard.
Synthetic Aperture Radar Interferometry (InSAR) is a satellite-based method for detecting deformation of the Earth’s surface and has excellent spatial coverage compared to GPS and other point measurements. InSAR measurements of surface displacements using the German Space Agency (DLR) TerraSAR-X (TSX) satellite were used to identify and analyze small-scale surface deformation at Kīlauea’s summit eruptive vent during June 2008 to February 2012. We calculated displacements over time using the SBAS approach and found variable subsidence of the vent rim over space and time, which may provide an indication of which portions of the summit eruptive vent are likely to fail in future collapses.
Fig. 1: Map of Kīlauea Volcano, its two rift zones, and the currently active eruptive sites. Zoomed map focuses on Kīlauea Caldera and shows the location of the
Halema‘uma‘u Crater with the summit eruptive vent on its east wall.
T32
1
Summit eruptive vent
32
654
150 300 450 600 750 900 1050 12001200
Distance in m
150
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Dist
ance
in m
Halema‘uma‘u Crater
1 km0.5 km0 km
-16
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0
2008 2009 2010 2011 2012
Defo
rmati
on in
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OS)
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T24 - Descending Orbit
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OS)
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T32 - Ascending Orbit
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T24
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Halema‘uma‘u Crater
Summit eruptive vent
4 35
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Dist
ance
in m
Distance in m
1 km0.5 km0 km
LOS displacement
0 1,55 cm
LOS displacement
0 1,55 cm
Fig. 3: Evolution of the summit vent rim deformation from TerraSAR-X SBAS time series analysis. The mean annual velocity maps (left side) and time series graphs (right side) show the average linear velocities for selected pixels, located at the
summit vent‘s rim that are unsteady over time. From that, line-of-sight subsidence of portions of the vent rim is obvious. Red dashed lines mark explosive events that occurred from the summit vent during 2008 and in early 2011.
The X-band (3.1 cm wavelength) TerraSAR-X data have the advantage of very high spatial and temporal resolution (pixel size ~2 m and repeat time of 11 days, compared to ~6-20 m and 46-35 days for the Japanese ALOS and European Space Agency Envisat satellites, respectively). To take advantage of this high spatial resolution, we used a 1-m resolution digital elevation model (DEM) from LIDAR data acquired in 2009 to construct interferograms with an unpreceded spatial resolution of 3 m for Kīlauea’s summit area using the two-pass DInSAR method.
Line-of-sight subsidence of the rim of the summit eruptive vent is obvious in all pixels considered. For each track there are pixels that become incoherent well before the end of the time series, presumably because the rim in these areas collapsed.
There is one pixel (pixel 5 of T24) considered in our analysis that becomes incoherent contemporaneously with an explosive eruption (on January 17, 2011).
There is no clear sign of an acceleration in subsidence prior to the pixels becoming incoherent, which might indicate an imminent failure; however, the subsidence rate is higher for pixels that become incoherent before the end of the time series compared to those that are coherent for the entire period.
Data since mid-2011 show little deformation, suggesting that the vent rim is relatively stable right now. Pixel 3 in T32 shows an acceleration of susidence in early 2011, a period that was characterized by numerous wall rock collapses due to the high lava levels.
In early 2011, most of the points that are still coherent (pixels 1, 2 and 3 of T24 and pixels 2 and 3 of T32) show deviations from the overall trend of the deformation, which is caused by displacement associated with the 5-9 March Kamoamoa fissure eruption.
Conc
lusi
on
We found steady subsidence of portions of the rim, with small interruptions due to changes in the volcano’s activity, with a rate of up to 17 cm over the course of about 37 months (June 2008–July 2011). The most recent data (mid-2011–February 2012) shows relative stability of the vent’s rim and wall, a result consistent with visual observations from a Webcam recording the vent from the Halema’uma’u overlook.
With the method shown here, we are monitoring the stability of the summit eruptive vent over time. We recommend continued observation of the summit eruptive vent using the approach provided in this study to assess periods of increased likelihood of summit vent collapse.
Our results demonstrate excellent prospects for continued use of TerraSAR-X, or systems with comparable spatial and temporal resolutions, such as COSMO-SkyMed, as an operational volcano monitoring and research tool, particularly at locations where small-scale deformation is an important indicator of volcanic activity.
I would like to take this opportunity to congratulate HVO, both past and current HVO staff, on 100 years of successful monitoring and research of Hawaiian volcanism, ensuring that Hawaiian volcanoes are and remain among the best-studied volcanoes on Earth.
SBAS time series data allow us to monitor vent stability over time. The analysis of the data yields several significant results (Fig. 3):
Hau‘oli lā hānau!
A
B
C
Kīlauea Caldera Halema‘uma‘u Crater
Summit eruptive vent
1 km 1 km
Summit eruptive vent instability
N
LOS displacement
0 1,55 cm
0 1,55 cm
LOS displacement
