SATELLITE MONITORING OF THE 2011 PUYEHUE...
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Table1: ENVISAT interferometric pairs and their spatial baseline 07/02/2011 09/03/2011 08/04/2011 08/05/2011 07/06/2011 07/07/2011 06/08/2011 05/09/2011 05/10/2011 04/12/2011 07/02/2011 89m 09/03/2011 251m 08/04/2011 244m 08/05/2011 98m 07/06/2011 153m 07/07/2011 50m 06/08/2011 206m 05/09/2011 92m 05/10/2011 187 04/12/2011 SATELLITE MONITORING OF THE 2011 PUYEHUE ERUPTION: FROM SAR TO OPTICAL SENSORS Bignami C. 1 , Corradini S. 1 , Merucci L. 1 , Piedra J. 2 , De Michele M. 3 , Raucoules D. 3 , Stramondo S. 1 1 INGV 2 Gulich Institute, CONAE 3 BRGM ABSTRACT : Chile has more than 2000 volcanoes, 500 of them considered geologically active with 60 historical eruptive records in the last 450 years. Chile has currently twelve active volcanoes with low eruptive activity (Lascar, San Pedro-San Plablo, Headed Grande-Cerro Azul-Quizapu, Planchon Peteroa Antuco Calbuco, Chaitén, Hudson, Villarrica, Lonquimay-Tolhuaca Choshuenco Mocho, Osorno) and two with middle eruptive activity (Puyehue-Cordon Caulle, Llaima). Among these volcanoes, we focus our work on the complex Puyehue - Cordon Caulle. Such complex is located in the province of Ranco, Region of Los Rios, and it consists of volcanic centers aligned northeast-southwest direction, and covers an area of 40 km2. In the northeast corner of the complex, we find the volcano Cordillera Nevada, in the central section is the Caulle - a fissure system that has delivered large volumes of lava – and in the extreme south is the Puyehue stratovolcano. Like most of stratovolcanoes on the Southern Volcanic Zone of the Andes, Puyehue and Cordón Caulle are located along the intersection of a traverse fault with the larger north-south Liquiñe-Ofqui Fault. On June 2011, Puyehue volcano began erupting. On 4 June, seismicity increased to an average of 230 earthquakes per hour, at depths of 1-4 km. About 12 events were magnitudes greater than 4, and 50 events were magnitudes greater than 3. The Alert Level was raised to 5. Explosion from Cordón Caulle produced a 5-km-wide ash-and-gas plume that rose to an altitude of 12.2 km. During 4-5 June an ash fall of several centimeters thick was reported in surrounding areas. On 7-8 July explosions were recorded and ash plum was present, reaching 2-3 Km altitude. The eruption continued on the next months. Currently, the seismicity recorded at the volcano continues decreasing trend, remaining at a low level of activity and energy compared to previous months. However, it still remains the possibility of minor explosive events generated. The current study reports the observation and analysis based satellite remote sensing application. In particular we exploited SAR interferometric technique (InSAR) to detect and to measure terrain movements. A series of SAR images acquired by ENVISAT platform, between May and December 2011 (about one image per month) have been processed to infer the displacement occurred during the eruption. Soon after the eruption beginning we found a maximum deflation of about 65 cm, clearly localized at the north-west area with respect the Puyheue caldera. The deformation decreased in the following months, reaching -20 cm on December. In addition, optical images captured by the MODIS sensors have been used to extract ash and gas emissions. The information gathered by both type of sensors allowed to highlight the relationship between surface deformation and the amount of ash and gases emitted by the volcano. 50 55 60 65 70 75 80 85 90 95 0.0E+00 5.0E+04 1.0E+05 1.5E+05 2.0E+05 2.5E+05 3.0E+05 3.5E+05 4.0E+05 4.5E+05 LOS monthly deflation [cm] Mass [t] Ash Mass SO2 Mass @7.3 mircons SO2 Mass @8.6 microns ENVISAT LOS deformation 0 5 10 15 20 25 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Plume altitude [km] Effective radius [microns] / AOD Effective Radius AOD Plume Altitude ENVISAT-ASAR & Cosmo-SkyMed data analysis: deformation and change detection The monthly acquisitions of ENVISAT-ASAR (February-December 20129) allowed the estimation of the deformation occurred during the eruption. Standard DinSAR processing has been applied to IS6 mode images. A multi-look factor of 6 az. X 2 rg , leading to 25m per pixel resolution; the topographic phase component has been removed by using the SRTM DEM. Due to low coherence, the deformation measurements have been obtained only for 4 SAR pair (see table 1). Left column reports the wrapped interferograms and right column reports the measured deformations. The red triangle corresponds to the new vent. First row refers to images taken on May 8-April 8, 2011. This is the last phase of inflation where few cm are captured by the interferogram. Second row refers to images taken on May 8-June 7, 2011. This is the most complex pattern of fringe of the entire sequence. It is possible to see the deformation resulting from the beginning of eruption, on June 4, 2011. The interferogram points out a deflating areas in the Cordon Caulle with a maximum value of -90 cm. Few cm of deflation are also present in the west flank of Puyehue mountain, well identified by the wrapped phase on the left column map. This latter shows also a small concentric fringe pattern in the NNE area in front of the new vent which is inflating (max 12 cm up). The second images pair shows the deformation measured between June 7-July 7. The deflation pattern is similar to the previous one but elongated towards the Puyehue volcano (South-East direction). The deflation value is noticeably reduced to a peak value of -55 cm. The last pair corresponds to the interferogram obtained from the images acquired on October 5 and December 4. The deflating area is still on the Cordon Caulle complex, but the maximum deformation value (about -20 cm) is shifted towards South-East. From the last three interferograms we guess the activity of Puyehue decreased in the observed period, as depicted in the plots on the right. no coherence interferograms strong atmo effects (likely due to march scene) good interferograms – figures below Ash detection and retrieval using Optical and SAR satellite images The MODIS ash detection is realized by using the BTD technique (Prata, 1989) that exploit the different absorption in the channels centred around 11 and 12 mm. The detection is possible only in case of meteorological cloud free scenes or when the volcanic cloud lies over the meteo clouds. When the volcanic cloud is completely covered by the meteo clouds the optical data are useless. In this latter case the SAR images can be used to detect the volcanic cloud near the vents. SAR images have also been exploited to obtain change detection maps (CDM). The CMD highlighted the evolution of the lava front in the surrounding area of the vent as showed in the last figures of the panel below. The VHR resolution images of COSMO –SkyMed, followed the first 20 days lava deposition (see first figure of the panel above; Red= June19, Green=Blue=June 26). The other 4 RGB false colour compositions have been obtained by assigning the May 5 image of ENVISAT to the Red channel, while the Blue and Green channels correspond to July 7, August 6, September 5 and October 5 acquisitions, respectively. The October image did not show significative modification in the lava front, which means that the effusive phase of the eruption stopped between September and October. Table2: COSMO-SkyMed used data date time looking direction & orbit polarization 2011-06-10 22:40:30 left – descending VV 2011-06-12 10:46:16 left – ascending HH 2011-06-19 22:40:27 left – descending HH 2011-06-26 22:40:24 left – descending HH The available COSMO-SkyMed images, unfortunately did not allowed DInSAR processing. Only two images have been acquired in the same modality on June 19 and 26, but – despite one week temporal separation – the strong loss of coherence hampered the interferogram generation. The red pixels in the MODIS BTD images indicate the volcanic ash presence The complete meteo cloud cover of the 07 June at 04:05 UTC MODIS image doesn’t allow the ash detection using optical data. The ash cloud can be detected by using the near contemporary ENVISAT-ASAR image, collected at 03:49 UTC (figure on the right). As the ENVISAT_ASAR images, also the COSMO-SkyMed images can be used to detect the volcanic clouds in case of meteo cloud cover. Ash /SO2 retrieval and correlation with surface deformation The MODIS ash retrievals (mass , effective radii and AOD) are based on computing the simulated inverted arches curves BTD vs brightness temperature at 11 mm varying the AOD and the particles effective radius (Wen and Rose, 1994). The optical properties are computed considering the Obsidian refractive index (Pollack, 1973), a log-normal distribution and applying the Mie theory. The SO2 columnar abundance is carried out by using a weighted least squares fit procedure (Realmuto et al., 1994) considering the MODIS channels centered around 7.3 and 8.7 mm (ch 28 and 29). An ash correction is applied to avoid the SO2 retrievals overestimation due to the ash presence (Corradini et al., 2009). For each image pixel, containing both SO2 and ash, the least square fit procedure is applied by taking onto account the AOD and effective radius computed from the pixel itself. MODIS-Aqua, 06 June 2011, 18:40 UTC MODIS-Terra, 07 June 2011, 04:05 UTC MODIS-Terra, 07 June 2011, 15:10 UTC RGB (ch 28, 29, 31) BTD (ch 31, 32) RGB (ch 28, 29, 31) BTD (ch 31, 32) RGB (ch 28, 29, 31) BTD (ch 31, 32) MODIS-Aqua, 05 June 2011, 05:55 UTC MODIS-Aqua, 10 June 2011, 18:15 COSMO, 10/06/11, 22:40 UTC RGB (ch 28, 29, 31) BTD (ch 31, 32) ENVISAT, 7/6/11, 3:49 UTC The method proposed in De Michele et al. 2013, has been used to detect the ash cloud on ENVISAT C-band SAR acquisition. It is worth to note that ash plume is not visible in the backscattering image. Figure on the left reports the sub-aperture azimuth pixel shift due to an anomaly in the Doppler history during the Synthetic Aperture. From this analysis we guess that the plume is oriented to SSE, providing additional information on the ash where the could cover hampers the detection with optical data. For details on the adopted methodology refer to 2‐P‐241 (here by the side). The X-band SAR image of COSMO-SkyMed, clearly detects the ash cloud in the proximity of the vent. The backscattering attenuation shows the Eastward direction of the plume, coherently with the MODIS- Aqua image acquired on the same day few hours before the COSMO-SkyMed pass. The Doppler anomaly method used for ENVISAT image, seems not work properly for X-band data. Further study are on going to point out the feasibility of the Dppler anomaly on X-band data The ash/SO2 total masses and the mean AOD/effective radius plotted are computed considering the first 300 km from the vent. The SAR deformation and the ash/SO2 masses retrieved show a similar exponential behaviour than an evident correlation. Unfortunately the low SAR revisit time (approximately 1 image per month) doesn’t allow to verify the rapid decay observed by MODIS from 6 to 11 June. SENTINEL-1 mission is expected to give a significative impact on this analysis allowing 6 days revisit time. Also the plume altitude and the mean AOD show the same exponential trend observed for the ash/SO2 masses, while for the mean effective radius the exponential decay is less evident.
Transcript of SATELLITE MONITORING OF THE 2011 PUYEHUE...
Table1: ENVISAT interferometric pairs and their spatial baseline 07/02/2011 09/03/2011 08/04/2011 08/05/2011 07/06/2011 07/07/2011 06/08/2011 05/09/2011 05/10/2011 04/12/2011
07/02/2011 89m
09/03/2011 251m
08/04/2011 244m
08/05/2011 98m
07/06/2011 153m
07/07/2011 50m
06/08/2011 206m
05/09/2011 92m
05/10/2011 187
04/12/2011
SATELLITE MONITORING OF THE 2011 PUYEHUE ERUPTION: FROM SAR TO OPTICAL SENSORS
Bignami C.1, Corradini S. 1, Merucci L. 1, Piedra J. 2, De Michele M. 3, Raucoules D. 3, Stramondo S. 1 1 INGV
2 Gulich Institute, CONAE 3BRGM
ABSTRACT : Chile has more than 2000 volcanoes, 500 of them considered geologically active with 60 historical eruptive records in the last 450 years. Chile has currently twelve active volcanoes with low eruptive activity (Lascar, San Pedro-San Plablo, Headed Grande-Cerro Azul-Quizapu, Planchon
Peteroa Antuco Calbuco, Chaitén, Hudson, Villarrica, Lonquimay-Tolhuaca Choshuenco Mocho, Osorno) and two with middle eruptive activity (Puyehue-Cordon Caulle, Llaima). Among these volcanoes, we focus our work on the complex Puyehue - Cordon Caulle. Such complex is located in the province of Ranco, Region of Los Rios, and it consists of volcanic centers aligned northeast-southwest direction, and covers an area of 40 km2. In the northeast corner of the complex, we find the volcano Cordillera Nevada, in the central section is the Caulle - a fissure system that has delivered large volumes of lava – and in the extreme south is the Puyehue stratovolcano. Like most of stratovolcanoes on the Southern Volcanic Zone of the Andes, Puyehue and Cordón Caulle are located along the intersection of a traverse fault with the larger north-south Liquiñe-Ofqui Fault. On June 2011, Puyehue volcano began erupting. On 4 June, seismicity increased to an average of 230 earthquakes per hour, at depths of 1-4 km. About 12 events were magnitudes greater than 4, and 50 events were magnitudes greater than 3. The Alert Level was raised to 5. Explosion from Cordón Caulle produced a 5-km-wide ash-and-gas plume that rose to an altitude of 12.2 km. During 4-5 June an ash fall of several centimeters thick was reported in surrounding areas. On 7-8 July explosions were recorded and ash plum was present, reaching 2-3 Km altitude. The eruption continued on the next months. Currently, the seismicity recorded at the volcano continues decreasing trend, remaining at a low level of activity and energy compared to previous months. However, it still remains the possibility of minor explosive events generated. The current study reports the observation and analysis based satellite remote sensing application. In particular we exploited SAR interferometric technique (InSAR) to detect and to measure terrain movements. A series of SAR images acquired by ENVISAT platform, between May and December 2011 (about one image per month) have been processed to infer the displacement occurred during the eruption. Soon after the eruption beginning we found a maximum deflation of about 65 cm, clearly localized at the north-west area with respect the Puyheue caldera. The deformation decreased in the following months, reaching -20 cm on December. In addition, optical images captured by the MODIS sensors have been used to extract ash and gas emissions. The information gathered by both type of sensors allowed to highlight the relationship between surface deformation and the amount of ash and gases emitted by the volcano.
50
55
60
65
70
75
80
85
90
95
0.0E+00
5.0E+04
1.0E+05
1.5E+05
2.0E+05
2.5E+05
3.0E+05
3.5E+05
4.0E+05
4.5E+05
LOS
mo
nth
ly d
efla
tio
n [c
m]
Mas
s [t
]
Ash Mass
SO2 Mass @7.3 mircons
SO2 Mass @8.6 microns
ENVISAT LOS deformation
0
5
10
15
20
25
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Plu
me
alti
tud
e [k
m]
Effe
ctiv
e ra
diu
s [m
icro
ns]
/ A
OD
Effective Radius
AOD
Plume Altitude
ENVISAT-ASAR & Cosmo-SkyMed data analysis: deformation and change detection The monthly acquisitions of ENVISAT-ASAR (February-December 20129) allowed the estimation of the deformation occurred during the eruption. Standard DinSAR processing has been applied to IS6 mode images. A multi-look factor of 6 az. X 2 rg , leading to 25m per pixel resolution; the topographic phase component has been removed by using the SRTM DEM. Due to low coherence, the deformation measurements have been obtained only for 4 SAR pair (see table 1).
Left column reports the wrapped interferograms and right column reports the measured deformations. The red triangle corresponds to the new vent. First row refers to images taken on May 8-April 8, 2011. This is the last phase of inflation where few cm are captured by the interferogram. Second row refers to images taken on May 8-June 7, 2011. This is the most complex pattern of fringe of the entire sequence. It is possible to see the deformation resulting from the beginning of eruption, on June 4, 2011. The interferogram points out a deflating areas in the Cordon Caulle with a maximum value of -90 cm. Few cm of deflation are also present in the west flank of Puyehue mountain, well identified by the wrapped phase on the left column map. This latter shows also a small concentric fringe pattern in the NNE area in front of the new vent which is inflating (max 12 cm up). The second images pair shows the deformation measured between June 7-July 7. The deflation pattern is similar to the previous one but elongated towards the Puyehue volcano (South-East direction). The deflation value is noticeably reduced to a peak value of -55 cm. The last pair corresponds to the interferogram obtained from the images acquired on October 5 and December 4. The deflating area is still on the Cordon Caulle complex, but the maximum deformation value (about -20 cm) is shifted towards South-East. From the last three interferograms we guess the activity of Puyehue decreased in the observed period, as depicted in the plots on the right.
no coherence interferograms
strong atmo effects (likely due to march scene)
good interferograms – figures below
Ash detection and retrieval using Optical and SAR satellite images
The MODIS ash detection is realized by using the BTD technique (Prata, 1989) that exploit the different absorption in the channels centred around 11 and 12 mm. The detection is possible only in case of meteorological cloud free scenes or when the volcanic cloud lies over the meteo clouds. When the volcanic cloud is completely covered by the meteo clouds the optical data are useless. In this latter case the SAR images can be used to detect the volcanic cloud near the vents.
SAR images have also been exploited to obtain change detection maps (CDM). The CMD highlighted the evolution of the lava front in the surrounding area of the vent as showed in the last figures of the panel below. The VHR resolution images of COSMO –SkyMed, followed the first 20 days lava deposition (see first figure of the panel above; Red= June19, Green=Blue=June 26). The other 4 RGB false colour compositions have been obtained by assigning the May 5 image of ENVISAT to the Red channel, while the Blue and Green channels correspond to July 7, August 6, September 5 and October 5 acquisitions, respectively. The October image did not show significative modification in the lava front, which means that the effusive phase of the eruption stopped between September and October.
Table2: COSMO-SkyMed used data
date time looking direction & orbit polarization
2011-06-10 22:40:30 left – descending VV
2011-06-12 10:46:16 left – ascending HH
2011-06-19 22:40:27 left – descending HH
2011-06-26 22:40:24 left – descending HH
The available COSMO-SkyMed images, unfortunately did not allowed DInSAR processing. Only two images have been acquired in the same modality on June 19 and 26, but – despite one week temporal separation – the strong loss of coherence hampered the interferogram generation.
The red pixels in the MODIS BTD images indicate the volcanic ash presence
The complete meteo cloud cover of the 07 June at 04:05 UTC MODIS image doesn’t allow the ash detection using optical data. The ash cloud can be detected by using the near contemporary ENVISAT-ASAR image, collected at 03:49 UTC (figure on the right).
As the ENVISAT_ASAR images, also the COSMO-SkyMed images can be used to detect the volcanic clouds in case of meteo cloud cover.
Ash /SO2 retrieval and correlation with surface deformation
The MODIS ash retrievals (mass , effective radii and AOD) are based on computing the simulated inverted arches curves BTD vs brightness temperature at 11 mm varying the AOD and the particles effective radius (Wen and Rose, 1994). The optical properties are computed considering the Obsidian refractive index (Pollack, 1973), a log-normal distribution and applying the Mie theory. The SO2 columnar abundance is carried out by using a weighted least squares fit procedure (Realmuto et al., 1994) considering the MODIS channels centered around 7.3 and 8.7 mm (ch 28 and 29). An ash correction is applied to avoid the SO2 retrievals overestimation due to the ash presence (Corradini et al., 2009). For each image pixel, containing both SO2 and ash, the least square fit procedure is applied by taking onto account the AOD and effective radius computed from the pixel itself.
MODIS-Aqua, 06 June 2011, 18:40 UTC MODIS-Terra, 07 June 2011, 04:05 UTC MODIS-Terra, 07 June 2011, 15:10 UTC
RGB (ch 28, 29, 31)
BTD (ch 31, 32)
RGB (ch 28, 29, 31)
BTD (ch 31, 32)
RGB (ch 28, 29, 31)
BTD (ch 31, 32)
MODIS-Aqua, 05 June 2011, 05:55 UTC
MODIS-Aqua, 10 June 2011, 18:15
COSMO, 10/06/11, 22:40 UTC
RGB (ch 28, 29, 31)
BTD (ch 31, 32)
ENVISAT, 7/6/11, 3:49 UTC
The method proposed in De Michele et al. 2013, has been used to detect the ash cloud on ENVISAT C-band SAR acquisition. It is worth to note that ash plume is not visible in the backscattering image.
Figure on the left reports the sub-aperture azimuth pixel shift due to an anomaly in the Doppler history during the Synthetic Aperture.
From this analysis we guess that the plume is oriented to SSE, providing additional information on the ash where the could cover hampers the detection with optical data.
For details on the adopted methodology refer to 2‐P‐241 (here by the side).
The X-band SAR image of COSMO-SkyMed, clearly detects the ash cloud in the proximity of the vent. The backscattering attenuation shows the Eastward direction of the plume, coherently with the MODIS-Aqua image acquired on the same day few hours before the COSMO-SkyMed pass.
The Doppler anomaly method used for ENVISAT image, seems not work properly for X-band data. Further study are on going to point out the feasibility of the Dppler anomaly on X-band data
The ash/SO2 total masses and the mean AOD/effective radius plotted are computed considering the first 300 km from the vent. The SAR deformation and the ash/SO2 masses retrieved show a similar exponential behaviour than an evident correlation. Unfortunately the low SAR revisit time (approximately 1 image per month) doesn’t allow to verify the rapid decay observed by MODIS from 6 to 11 June. SENTINEL-1 mission is expected to give a significative impact on this analysis allowing 6 days revisit time. Also the plume altitude and the mean AOD show the same exponential trend observed for the ash/SO2 masses, while for the mean effective radius the exponential decay is less evident.
