InSAR Imaging of Aleutian Volcanoes: Monitoring a Volcanic Arc from Space

411 Pages·2014·76.96 MB·English

by  Zhong Lu

InSAR Imaging of
Aleutian Volcanoes
Monitoring a Volcanic Arc
from Space
Zhong Lu
Daniel Dzurisin
Springer Praxis Books
Geophysical Sciences
For furthervolumes:
http://www.springer.com/series/4110
RoilingeruptioncolumnrisingfromCraterPeakventofMountSpurronAugust18,1992.Viewisfromthe
south.SatelliteInSARwasinitsinfancyatthetimeandwewereunabletodetectanygrounddeformation
associatedwiththeeruptionbecauseonlyafewSARimageswereavailableandperennialsnowresultedin
coherence loss. The situation had improved by 2004–2005, when a shallow intrusion of magma beneath
MountSpurrwasaccompaniedbyelevatedseismicity,heatflux,andmagmaticgasemission.Bythattimethe
numberofoperationalSARsatelliteshadincreasedanddataanalysistechniqueshadadvancedconsiderably.
As a result, we were able to map a broad uplift signal and attribute it to inflation of a magma reservoir
10–14km BSL—presumably the source of the intrusion. Subsequent InSAR analyses have shown that the
AlaskaPeninsulaandCookInletregionfromtheKatmaivolcanicclustertoMountSpurrisamongthemost
actively deforming sections of the Aleutian arc. Photo by Game McGimsey, Alaska Volcano Observatory/
U.S.GeologicalSurvey
Zhong Lu Daniel Dzurisin
•
InSAR Imaging of Aleutian
Volcanoes
Monitoring a Volcanic Arc from Space
123 Published in association with
Praxis Publishing
Chichester, UK
ZhongLu Daniel Dzurisin
US GeologicalSurvey, US GeologicalSurvey,
Cascades VolcanoObservatory Cascades VolcanoObservatory
Vancouver,WA Vancouver,WA
USA USA
Currentaddress
ZhongLu
RoyM. HuffingtonDepartment
of Earth Sciences
SouthernMethodistUniversity
Dallas,TX
USA
ISSN 1615-9748
ISBN 978-3-642-00347-9 ISBN 978-3-642-00348-6 (eBook)
DOI 10.1007/978-3-642-00348-6
Springer Heidelberg NewYork Dordrecht London
LibraryofCongressControlNumber:2013956517
(cid:2)Springer-VerlagBerlinHeidelberg2014
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Science is a social process. It happens on a time scale longer than
a human life. If I die, someone takes my place. You die;
someone takes your place. What’s important is to get it done.
Alfred Lothar Wegener, visionary German scientist who paved
the way for development of modern plate tectonics theory with
his continental drift hypothesis. In 1915, Wegener published his ideas
on the breakup and dispersal of a protocontinent he named Pangaea.
His work, The Origin of Continents and Oceans (Die Entstehung der
Kontinente und Ozeane), met with general skepticism and remained
obscure until long after his death in 1930—until compelling evidence
for plate tectonics emerged in the 1960s.
Daniel J. (‘‘Dan’’ or ‘‘DJ’’) Johnson and Anthony (‘‘Tony’’) Qamar died
tragically in a highway mishap on October 4, 2005, en route to retrieve
Global Positioning System (GPS) equipment deployed on the Olympic
Peninsula in western Washington State, USA, to study an episodic tremor and
slip (ETS) event. Dan, a research professor at the University of Puget Sound,
brought a keen intellect and unbridled enthusiasm to his studies on ground
deformation in Hawaii, the Pacific Northwest, Galápagos Islands, and
elsewhere. As Washington state seismologist and research professor at the
University of Washington, Tony was a soft-spoken but widely recognized
expert on Pacific Northwest earthquakes and volcanoes, a caring mentor to
his students, and an accomplished mountain climber. Their work on ETS
events anderuptions atMountSt.Helensadvanced understandingofhowand
why the Earth deforms—a lasting contribution to be cherished by colleagues,
students, and friends
In memory of Daniel J. Johnson and Anthony Qamar
Foreword
Having worked with USGS colleagues Zhong Lu and Dan Dzurisin throughout our
careers in volcanology and tectonics, we were delighted to be asked to review this
exciting compilation of InSAR studies of Alaskan volcanoes. Our professional experi-
ences with the authors cover a wide range of interactions, from brainstorming expla-
nations for interferograms showing dramatic volcano-wide deformation patterns in the
CascadesandAlaskatohotdaysinthefieldexaminingtephrapitsatKilaueaVolcano.
Zhong and Dan’s enthusiasm for solving the mysteries of volcanoes using systematic
observations, mathematical precision, and conceptual models is evident in their prolific
publication records. In this lively and engaging book, both a primer and a compilation
ofpublishedandunpublishedresultsofInSARinsightsintovolcanoesoftheAleutians,
we are treated to their latest ideas on how volcanoes, and volcanic arcs, work.
Inthelate1990s,whenapplicationofsatelliteInSARwasinitsinfancy,itseemedto
some practitioners that the Alaskan volcanoes would prove to be poor InSAR targets.
The volcanoes of Alaska received too much snow every year, they had too much
permanent ice, and the Alaskan summers were too short to acquire a useful set of
coherent interferograms. Luckily however, a combination offactors enabled InSAR to
work there very well. There is enough bare (or nearly bare) rock and soil with C-band
radar scatterers in the brief Alaskan summers to yield year-to-year coherence in inter-
ferograms. Also, there is an abundance of satellite radar data available over the
volcanoes, thanks to the space agencies of Europe, Canada, and Japan, and to the
Alaska Satellite Facility in Fairbanks, Alaska (with support from NASA). Together,
these factors enabled Lu and Dzurisin to ferret out useful information about ground
deformation, or lack thereof, at most of the arc’s historically active volcanoes.
To accomplish that task, they combined relentless data management skills (witness the
*25,000interferogramsproducedfortheAlaskanvolcanoes)withexpertknowledgeof
volcanoes and how/why they deform. It also helps that there are a plentiful number of
deforming and erupting volcanoes in Alaska.
The Aleutian arc includes more than 50 historically active volcanoes along the
dramatic, 2,500-km-long sweep of islands, peninsula, and mountains that define the
northernmostportionofthecircum-PacificRingofFire.Overthepast40 years,during
a time when observational records are fairly complete, Alaska has experienced an
average of more than two eruptions per year. It is, quite simply, a tremendous natural
laboratory for the study of active volcanism. When an Alaskan volcano becomes rest-
less, volcanologists at the Alaska Volcano Observatory (AVO) are confronted with
questionsthat,despiteenormousadvancesinourunderstandingofhowvolcanoeswork,
remain quite difficult to answer with certainty: Will this episode of unrest end in erup-
tion?Ifso,whenwillitcommence?Howbigwillitbeandhowlongwillitlast?Forsome
years now, a standard procedure at AVO has been to quickly contact Zhong Lu and
Dan Dzurisin to seek the latest InSAR results for the volcano showing unrest. Can
InSAR augment our ground-based seismic and other monitoring data? Can surface
ix
x Foreword
deformationindicativeofmagmaticintrusion—perhapssuspectedbasedonseismicity—
beconfirmedorconstrained?Notsurprisingly,space-basedgeodeticinsightisespecially
helpful in monitoring Alaska’s distant and remote volcanic islands, where installation
andmaintenanceofground-basedGPSnetworksandseismometersremainquitecostly.
Usuallywithinaveryshorttime,AVOreceivesanewinterferogramresulttoaddtothe
discussion and interpretation of available data, providing another clue as we grapple
with providing hazard statements to those at risk.
Now,afternearlytwodecadesand12,000SARimagesfromsevendifferentsatellites,
Lu and Dzurisin have compiled results for most of the Holocene volcanoes in the
Aleutianarc.Inthisrichlyillustratedbook,theauthors’passionforunderstandinghow
the Earth works and particularly how volcano deformation can help image magmatic
systemsandforecasteruptionscomethroughloudandclear.Theybeginwithsystematic
treatments of the theory and practice of InSAR, its mathematical foundations, data
processing, error correction, and generation of interferograms and digital elevation
models (DEMs). Readers are then treated to an instructive and entertaining account of
the history of plate tectonic concepts, rich with engaging anecdotes about the scientific
process. A description of Aleutian tectonics sets the stage, and then the authors sail up
the arc, west to east from Kiska to Wrangell, summarizing 20 years of InSAR obser-
vation for each volcanic center. They integrate these results with eruption chronologies
and geologic-petrologic-geophysical studies, and then offer conceptual models of each
volcano’s magmatic system to test, refine, and call upon during episodes of unrest. The
book’s finale is a synthesis of broad conclusions based on InSAR-derived patterns of
Aleutian volcano deformation. Elegant in their simplicity, these insights offer volca-
nologists and other Earth scientists worldwide benchmark concepts to consider when
interpreting individual volcano dynamics and whole-arc behavior from source to sur-
face. Aleutian arc specialists, including those whose ideas they incorporate into this
synthesis, will especially enjoy debating the authors’ provocative conceptual models to
explain changing volcano behavior and deformation styles along the arc.
Weknowthisbook willfind awelcome homeonshelvesofvolcanologistsandother
Earth scientists of diverse specializations. True to their interdisciplinary roots, the
authorsspeaktospecialistsandgeneralistsalike,makingaclearcasethatintegrationof
multiple modes of observation is the key to improving our understanding of how vol-
canoes work. InSAR, with its powerful ability to provide a synoptic, volcano-scale
snapshot of the deformation field with time is rapidly becoming a critical Earth science
tool. It certainly has become part of the standard volcano observatory practice when
accesstosatellitedataexists.Infact,thesystematic(automatic?)useofInSARtodetect
premonitory signs of unrest at volcanoes worldwide may not be far off.
ThisbookismorethanatreatiseonInSARappliedtoAlaskanvolcanoes,itisalsoa
journey of scientific discovery. The motivation to produce a single interferogram is the
excitementofseeingwhatthatinterferogramcanrevealabouttheworkingsofavolcanic
system.Togenerateandponderthemeaningofthousandsofinterferogramstoadvance
our understanding of volcanoes is simply inspiring. We are honored to share with the
authors a small part of their journey by recalling our respective experiences with
Alaskan volcanoes and InSAR to help fine-tune the book.
Christina Neal
Chuck Wicks
Preface
IfIcouldexplainittotheaverageperson,Iwouldn’thavebeenworththeNobelPrize.
RichardP.Feynman
1965NobellaureateinPhysics
People,22July1985
Richard Feynman certainly was worth the Nobel Prize and we assuredly are not. We’ll
takethataslicenseforthisattemptto‘‘…explainittotheaverageperson.’’Itforusisnot
quantum electrodynamics but InSAR, the seemingly magical geodetic camera, and
specifically its application to the diverse volcanoes of the Aleutian volcanic arc. InSAR
is shorthand for interferometric synthetic aperture radar, a tongue twister of a remote
sensingtechniquethathasrevolutionizedstudiesofEarth’slandsurface,includingthose
most fascinating of dynamic landforms called volcanoes. More than 50 historically
active volcanoes are found in the Aleutian arc, which stretches from the Kamchatka
Peninsula eastward to Alaska to form the northern part of the Pacific ‘‘Ring of Fire.’’
Aleutian volcanoes range from stately basaltic stratocones that erupt frequently and
quietlyforthemostpart,tognarlysilicicsystemsthatcanliedormantforthousandsof
yearsbeforeproducingenormouseruptionsliketheonethatformedtheKatmaicaldera,
Novarupta dome, and Valley of Ten Thousand Smokes in 1912—the largest twentieth-
century eruption on Earth.
InSARenablesustoexaminetherichdiversityofAleutianvolcanoesthroughasingle
lens, as it were, and to muse about similarities and differences in such things as defor-
mationstyle, eruptionfrequency,and magmaplumbingsystems.That’s what thisbook
is about, an initial attempt to sketch out generalizations about how Aleutian volcanoes
deformand,byextension,howtheymightwork.Towardthatend,wedrawfreelyupon
information from other disciplines, including geology, seismology, and geochemistry,
although we are expert in none of these. We trust that our colleagues will correct our
mistakes and continue to address the many questions we leave unanswered.
The‘‘averageperson’’forwhomthisbookisintendedincludesstudentsofvolcanoes,
remotesensing,geomorphology,andsurface-changeprocesses,amongothers.Wehope
thebookisbothusefultoresearchspecialistsandinterestingtovolcanoenthusiastswith
little or no formal training in the field. Some readers might want to consult our more
general treatment of InSAR in aprevious Springer Praxis book, Volcano Deformation—
GeodeticMonitoringTechniques(Dzurisin2007;DzurisinandLu2007).Ifso,you’llnote
continuedprogresssincethatwritingtowardreal-timeglobalvolcanosurveillance,using
InSAR and other remote sensing techniques together with expanded ground-based
monitoring systems. Since July 1992, European Space Agency has launched C-band
ERS-1(1991),ERS-2(1995),andEnvisat(2002)satellites,providingatreasuretroveof
radar images to allow scientists to study planet Earth. Japan Aerospace Exploration
Agency successfully launched JERS-1 and ALOS PALAR in 1992 and 2006, respec-
tively, providing outstanding L-band radar images that can be used to produce inter-
ferogramsforheavilyvegetatedareasthataremostlyoff-limits atC-bandowingtoloss
ofcoherence.Radarsat-1,theCanadianSpaceAgency’sfirstC-bandradarmission,was
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