Pyroclastic Flow Deposits and InSAR: Analysis of Long-Term Subsidence at Augustine Volcano, Alaska

David Mcalpin,Wenyu Gong,Franz Meyer,James Beget,Peter Webley

doi:10.3390/rs9010004

David Mcalpin, Wenyu Gong + Show 3 more

Open Access

https://doi.org/10.3390/rs9010004

Copy DOI

Abstract

Deformation of pyroclastic flow deposits begins almost immediately after emplacement, and continues thereafter for months or years. This study analyzes the extent, volume, thickness, and variability in pyroclastic flow deposits (PFDs) on Augustine Volcano from measuring their deformation rates with interferometric synthetic aperture radar (InSAR). To conduct this analysis, we obtained 48 SAR images of Augustine Volcano acquired between 1992 and 2010, spanning its most recent eruption in 2006. The data were processed using d-InSAR time-series analysis to measure the thickness of the Augustine PFDs, as well as their surface deformation behavior. Because much of the 2006 PFDs overlie those from the previous eruption in 1986, geophysical models were derived to decompose deformation contributions from the 1986 deposits underlying the measured 2006 deposits. To accomplish this, we introduce an inversion approach to estimate geophysical parameters for both 1986 and 2006 PFDs. Our analyses estimate the expanded volume of pyroclastic flow material deposited during the 2006 eruption to be 3.3 × 107 m3 ± 0.11 × 107 m3, and that PFDs in the northeastern part of Augustine Island reached a maximum thickness of ~31 m with a mean of ~5 m. Similarly, we estimate the expanded volume of PFDs from the 1986 eruption at 4.6 × 107 m3 ± 0.62 × 107 m3, with a maximum thickness of ~31 m, and a mean of ~7 m.

Highlights

Interferometric synthetic aperture radar (InSAR) is well established as a means for identifying terrain deformation associated with volcanic activity [1,2,3,4,5]
A set of M interferograms is first formed from the N + 1 images using InSAR processing, which calculates the phase difference φi,j between pairs of SAR images according to φi,j = φi − φ j where φi,j is the interferometric phase measurement calculated from SAR images i and j (i, j ∈ ( N + 1)
Our methodology was applied to examine the subsidence behavior of pyroclastic flow deposits (PFDs) from multi-sensor InSAR acquisitions acquired across two eruption cycles

Summary

Introduction

Interferometric synthetic aperture radar (InSAR) is well established as a means for identifying terrain deformation associated with volcanic activity [1,2,3,4,5]. InSAR processing can be used to measure changes in the surface deformation with centimeter to sub-centimeter accuracy at regional scales as terrains inflate and deflate with subsurface magma intrusion and extrusion [6,7], and at local scales as post-eruptive materials subside through compaction, degassing, and other mechanisms [8,9]. Lavas are flows of magma that have erupted at the Earth’s surface effusive volcanic activity [10]. Pyroclastic flows are produced by more violent explosive activity or gravitational dome collapse [11]. They can be described, generally, as hot, gravity controlled, rapidly moving flows of high particle-concentration ash and gas, and, in some instances, may be partly fluidized [10]

Objectives

Methods

Findings

Discussion

Conclusion