11:15 〜 11:30
[SVC28-03] Evolution of Volcanic Deformation at Domuyo and Laguna del Maule, Southern Andes, Revealed by InSAR Time-series Analyses
キーワード：InSAR, Volcano deformation, Volcanic unrest, Time-series, Source modeling
Introduction
“Los Andes” mountain range, in South America, hosts numerous volcanoes that present eruptive and non-eruptive activity. Recently, alarming episodes of unrest at Domuyo and Laguna del Maule volcanic complexes (DVC and MVC respectively) inferred from geophysical observations have been announced. According to Astort et al.[1] (2019), inflation has been recognized at DVC from 2014, while at MVC from 2007, both with rates that surpass 12 cm/year. Here, we follow up on the recent deformation using time-series analyses of InSAR images and estimate the source parameters by applying different models representing the magmatic system.
InSAR time-series analysis
InSAR time series and velocity estimates of surface deformation were obtained using an open-source SAR interferometry (InSAR) analysis package, LiCSBAS (Morishita et al.[2], 2020). It integrates with an automated Sentinel-1 InSAR processor, LiCSAR (Lazecký et al.[3],2020), that produces interferograms using GAMMA SAR and Interferometry software.
The LiCSAR frames processed for both DVC and MVC correspond to the IDs 018A_12668_131313 for the ascending orbit and 083D_12636_131313 for the descending orbit, covering a time interval of about six years, from October 2014 to January 2021, with a total amount of 660 and 835 interferograms, respectively.
From the LiCSBAS analysis for DVC, a large deformation area around the summit was recognized with mean velocity of 10 cm/year as for January 2021, lower than that in the previous studies (e.g. Astort et al.[1], 2019) and that has been almost constant or slowly decreasing since the start of 2020 as shown in the time-series. This could indicate the possible culmination of the period of unrest of the complex. The normalized LOS displacements were divided into four periods based on displacement rates: I) Jan-Dec 2015, II) Jan-Dec 2016, III) Jul 2017-Dec 2018, and IV) Jan-Dec 2019.
For MVC, we also recognize a large circular deformation area surrounding the summit in both the ascending and descending paths, with a mean velocity of ~21 cm/yr. Comparing the temporal evolution of LOS displacements with that of the DVC, we found that MVC presents a continuous growth almost at a constant rate through the years.
Model selection
For source model estimation we used Geodetic Bayesian Inversion Software (GBIS) which allows a rapid characterization of posterior probability density functions (PDFs) of model parameters (Bagnardi and Hooper[4], 2018). LOS displacement data from both satellite tracks were used, assuming different types of source models: point pressure (Mogi[5], 1958), rectangular dipping dike (Okada[6], 1985), prolate spheroid (Yang and Davis[7], 1988), and horizontal rectangular sill (Okada[6], 1985). We treated each of the periods independently and then compared the residuals obtained for each model and conclude that the lowest values were related to the horizontal sill model.
In the case of the DVC, no significant differences in the source locations, length (~10 km) and strike of the sill were found, in contrast with the depths that range between 7.9 and 8.8 km. The volume varies as 21, 41, 30 and 16 × 106 m3 from period I to IV respectively, supporting the assumption of the ending of the DVC episode of unrest due to the decreasing of the values in time.
Although for the MVC the location and depth (7 ±0.1 km) remained almost constant, the volume of the source increased from 25 to 39 × 106 m3. This could not only mean that the source of magma supply does not move but also it increases through time.
References
[1] Remote Sens. 2019, 11, 2175; doi:10.3390/rs11182175
[2] Remote Sens. 2020, 12, 424; doi:10.3390/rs12030424
[3] Remote Sens. 2020, 12, 2430; doi:10.3390/rs121524300
[4] GGG. 2018, 19, 2194-2211; doi: 10.1029/2018GC007585
[5] Bull. Earthq. Res. Inst. U. Tokyo. 1958, 36, 99–134
[6] BSSA. 1985, 75(4), 1135-1154
[7] JGR: Solid Earth, 1988, 93(B5), 4249-4257
“Los Andes” mountain range, in South America, hosts numerous volcanoes that present eruptive and non-eruptive activity. Recently, alarming episodes of unrest at Domuyo and Laguna del Maule volcanic complexes (DVC and MVC respectively) inferred from geophysical observations have been announced. According to Astort et al.[1] (2019), inflation has been recognized at DVC from 2014, while at MVC from 2007, both with rates that surpass 12 cm/year. Here, we follow up on the recent deformation using time-series analyses of InSAR images and estimate the source parameters by applying different models representing the magmatic system.
InSAR time-series analysis
InSAR time series and velocity estimates of surface deformation were obtained using an open-source SAR interferometry (InSAR) analysis package, LiCSBAS (Morishita et al.[2], 2020). It integrates with an automated Sentinel-1 InSAR processor, LiCSAR (Lazecký et al.[3],2020), that produces interferograms using GAMMA SAR and Interferometry software.
The LiCSAR frames processed for both DVC and MVC correspond to the IDs 018A_12668_131313 for the ascending orbit and 083D_12636_131313 for the descending orbit, covering a time interval of about six years, from October 2014 to January 2021, with a total amount of 660 and 835 interferograms, respectively.
From the LiCSBAS analysis for DVC, a large deformation area around the summit was recognized with mean velocity of 10 cm/year as for January 2021, lower than that in the previous studies (e.g. Astort et al.[1], 2019) and that has been almost constant or slowly decreasing since the start of 2020 as shown in the time-series. This could indicate the possible culmination of the period of unrest of the complex. The normalized LOS displacements were divided into four periods based on displacement rates: I) Jan-Dec 2015, II) Jan-Dec 2016, III) Jul 2017-Dec 2018, and IV) Jan-Dec 2019.
For MVC, we also recognize a large circular deformation area surrounding the summit in both the ascending and descending paths, with a mean velocity of ~21 cm/yr. Comparing the temporal evolution of LOS displacements with that of the DVC, we found that MVC presents a continuous growth almost at a constant rate through the years.
Model selection
For source model estimation we used Geodetic Bayesian Inversion Software (GBIS) which allows a rapid characterization of posterior probability density functions (PDFs) of model parameters (Bagnardi and Hooper[4], 2018). LOS displacement data from both satellite tracks were used, assuming different types of source models: point pressure (Mogi[5], 1958), rectangular dipping dike (Okada[6], 1985), prolate spheroid (Yang and Davis[7], 1988), and horizontal rectangular sill (Okada[6], 1985). We treated each of the periods independently and then compared the residuals obtained for each model and conclude that the lowest values were related to the horizontal sill model.
In the case of the DVC, no significant differences in the source locations, length (~10 km) and strike of the sill were found, in contrast with the depths that range between 7.9 and 8.8 km. The volume varies as 21, 41, 30 and 16 × 106 m3 from period I to IV respectively, supporting the assumption of the ending of the DVC episode of unrest due to the decreasing of the values in time.
Although for the MVC the location and depth (7 ±0.1 km) remained almost constant, the volume of the source increased from 25 to 39 × 106 m3. This could not only mean that the source of magma supply does not move but also it increases through time.
References
[1] Remote Sens. 2019, 11, 2175; doi:10.3390/rs11182175
[2] Remote Sens. 2020, 12, 424; doi:10.3390/rs12030424
[3] Remote Sens. 2020, 12, 2430; doi:10.3390/rs121524300
[4] GGG. 2018, 19, 2194-2211; doi: 10.1029/2018GC007585
[5] Bull. Earthq. Res. Inst. U. Tokyo. 1958, 36, 99–134
[6] BSSA. 1985, 75(4), 1135-1154
[7] JGR: Solid Earth, 1988, 93(B5), 4249-4257