Subject Area

Earth, Atmospheric and Marine Sciences

Abstract

Surface deformation mapping is an essential component for comprehensive monitoring of volcanic activities, serving as a vital tool for discerning crucial insights into magma dynamics, storage, and migration for accurate hazard forecasting, assessment, and mitigation. However, monitoring of the volcanic deformation across the Aleutian volcanic arc is usually limited by the lack of terrestrial sensors deployed due to their remote locations and hostile environmental conditions, necessitating alternative methodologies for data acquisition and analysis.

My PhD study aims at precisely mapping the crustal deformation for the Aleutian volcanoes and tracking the evolution of the magmatic system with Interferometric Synthetic Aperture Radar (InSAR) and numerical deformation modeling. Advanced timeseries InSAR algorithms are applied to three cases: Okmok, Makushin, and western and central Aleutian. Deformation history since the 2008 eruption at Okmok mapped with PSInSAR unveils several successive inflation episodes with time-dependent rates. Finite Element Models (FEM) updated with Ensemble Kalman Filter (EnKF) find the timeseries deformation can be well explained by a spherical source with temporally steady location about 3.5 km beneath the central caldera, with cumulative volume change about from 2008 to 2021.

Deformation mapped from SAR data collected across platforms have detected multiple inflation/deflation cycles characterized by temporally varying rates at Makushin volcano from 2004 to 2021. Inverse models of the crustal deformation suggest a Mogi source located to the northeast of the caldera at a depth ~6 km Beneath Sea Level (BSL). A shallow secondary deformation located to the southeast of the volcano, with rates about half that of the main deformation is also identified. A volatile intrusion/degassing dominated plumbing system is preferred by the inflation/deflation cycles with distinct magnitudes and lifetimes.

A new timeseries InSAR framework is developed based on the geocoded unwrapped interferograms produced from Jet Propulsion Laboratory (JPL) Advanced Rapid Imaging and Analysis (ARIA) system. Deformation histories for volcanoes in the western and central Aleutian are retrieved with this framework with Sentinel-1 imageries from 2015 to 2021. Various deformation patterns associated with different volcanic processes have been detected and used to track the evolution of volcanic systems. New deformation patterns are observed from Tanaga, Great Sitkin and Yunaska volcano. Overall higher magmatism, which may be attributed to spatial variation in tectonic environments, is identified in the central Aleutian.

To investigate the discrepancy between magmatic sources derived from geodetic deformation and the ones inferred from seismic tomography at Okmok, several numerical magma reservoir models are constructed and analyzed. The single reservoir model with magmatic chamber characterized by low P and S wave velocity (Vp and Vs) and moderate P to S wave velocity (Vp/Vs) ratio produce crustal deformation that fits the geodetic observations better than the distributed reservoir model with magma chambers represented by high Vp and Vp/Vs ratio and low Vs, which likely reconcile the geodetic deformation and seismic tomography observations and highlights the necessity of joint interpretation of geophysical observations over regions with complicated volcanic environments.

Degree Date

Spring 5-11-2024

Document Type

Dissertation

Degree Name

Ph.D.

Department

Earth Science

Advisor

Prof. Zhong Lu

Second Advisor

Prof. Brian Stump

Third Advisor

Dr. Jinwoo Kim

Fourth Advisor

Prof. Patricia Gregg

Fifth Advisor

Dr. Heresh Fattahi

Number of Pages

160

Format

.pdf

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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