Analysis of Magma Activity during the Cerro Azul Volcanic Unrest in March 2017 Using Sentinel-1 DInSAR Observations; Sentinel-1 DInSAR 관측을 활용한 2017년 3월 Cerro Azul 화산 불안 시기의 마그마 활동 분석

초록

Cerro Azul volcano, one of the most active volcanoes in the Galápagos Archipelago, exhibited significant unrest in March 2017, marked by dramatic displacement around the caldera and on the southeastern plain. This study applied differential interferometric synthetic aperture radar (DInSAR) technique to SAR image pairs acquired from the Sentinel-1A satellite’s ascending and descending nodes to measure the line-of-sight (LOS) and two-dimensional (up-down and east-west) displacements during the 2017 unrest of the volcano. Extensive concentric fringe patterns were observed around the caldera and on the southeastern plain of Cerro Azul volcano, indicating LOS displacements away from and toward the satellite, respectively. Two-dimensional displacements revealed that the volcanic body around the caldera contracted, while the southeastern plain uplifted and expanded. To further characterize magmatic activity during the unrest, we inverted LOS displacements from both ascending and descending observations using Mogi and Sill source models. The surface displacements simulated from the optimal magma source parameters obtained through inversion showed a normalized root mean square error of less than 5% compared to the DInSAR-observed displacements, confirming the reliability of the inversion results. The Mogi source was located approximately 4.7 km beneath the northeastern caldera rim of Cerro Azul and exhibited a volume change of –31 × 106 m3. The Sill source, characterized by a long rectangular shape approximately 10 km in length and 1 km in width, was situated about 7 km beneath the southeastern plain and showed a volume change of 68 × 106 m3. The volume increase of the Sill source was approximately twice that of the volume decrease of the Mogi source. Results of this study suggest that magma intrusion into the southeastern plain, originating from the Mogi source and deeper magma reservoirs, likely drove the 2017 unrest. This highlights the complex magmatic activity of Cerro Azul volcano and underscores the importance of continuous displacement monitoring to assess volcanic activity and associated hazards. © © 2024 Korean Society of Remote Sensing.

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