InSAR Imaging of Aleutian Volcanoes - ESA SEOMseom.esa.int/fringe2015/files/presentation117.pdf · InSAR Imaging of Aleutian Volcanoes ERS-1, ERS-2, JERS-1, Radarsat-1, Envisat, ALOS,

Acknowledgements: • Contributions by many colleagues. • SAR images from ESA, NASA/ASF, JAXA, CSA, and DLR.

InSAR Imaging of Aleutian Volcanoes:

Zhong Lu1 & Dan Dzursin2

1. Southern Methodist University 2. U.S. Geological Survey

Monitoring a volcanic arc from space

• Volcano deformation • Aleutian volcanoes • What we have learned about Aleutian volcanoes

from InSAR imaging

Outline

Volcano Deformation: Why?

1. Many volcanic eruptions are preceded by pronounced ground deformation in response to increasing pressure from magma chambers or to the upward intrusion of magma.

2. Surface deformation patterns can provide important insights into the structure, plumbing, and state of restless volcanoes.

3. Surface deformation might be the first sign of increasing levels of volcanic activity, preceding swarms of earthquakes or other precursors that signal impending intrusions or eruptions.

4. Surface deformation provides a critical element on understanding how a volcano work.

• InSAR can identify and monitor surface deformation at quiescent and active volcanoes.

• InSAR can derive models of magma migration consistent with surface deformation preceding, accompanying, and following eruptions to constrain the nature of deformation sources (e.g., subsurface magma accumulation, hydrothermal-system depressurization resulting from cooling or volatile escape).

• InSAR can monitor and characterize volcanic processes such as lava-dome growth and map the extent of eruptive products (lava and pyroclastic flows and ash deposits) from SAR backscattering and coherence imagery during an eruption, an important diagnostic of the eruption process. Similar methods can be used during or after an eruption to determine the locations of lahars or landslides.

• InSAR can map localized deformation associated with volcanic flows that can persist for decades to understand physical property of volcanic flows, guide ground-based geodetic benchmarks, and help avoid misinterpretations caused by unrecognized deformation sources.

InSAR Applied to Volcanoes

• Estimate source characteristics from InSAR deformation data

s

forward model InSAR image

displacement (vector)

source parameters

G s = d

design matrix

inverse model s = G d

inv

Deformation Modeling

~7 km

~50 - 200 km

Lu et al., JGR, 2003

Simple Source Models in Elastic Half-Space • Spherical Point Source • Prolate Ellipsoid • Sill or Dike for volcanoes • Penny-shaped Sill • Pipe • Distributed sources

Deformation Source Models

Complicating Effects • Non-uniform Elastic Structure • Topography • Viscoelasticity • Poroelasticity • Thermoelasticity • Complex Geometry • Influence of hydrothermal fluid

u = ƒ(model parameters, material properties, …, )

• Homogeneous • Elastic • Half-space

• Although the rate of eruptive activity is very high, deformation monitoring using GPS has been possible at only a few Aleutian volcanoes, owing to the remote location, hostile climate, difficult logistics, and high cost of field operations.

Aleutian Volcanoes • ~8% of the world’s active

volcanoes. • ~75% of the historically

active volcanoes in U.S. • ~2 eruptions per year in

the arc. • Aleutian volcanoes span

the entire spectrum in – eruptive style – eruption size/volume – magma composition

InSAR Imaging of Aleutian Volcanoes ERS-1, ERS-2, JERS-1, Radarsat-1, Envisat, ALOS, TerraSAR-X imagery of 1990s-2010 25,000 InSAR images plus modeling & analysis

• Lu and Dzurisin, Springer, 2014

Becharof Discontinuity

Historically active volcanoes: 52 No evidence of surface deformation:13 No useful information (decorrelation or poor spatial resolution): 8 Surficial deformation: 7 Magma intrusion: 21 + Strandline Lake Deep-source deflation: 3 Erupted volcanoes: 17 (1992-2010) In contrast to Cascades volcanic arc: Large volcanic centers: 12 Deformed volcanoes: 4 Eruption: 1

Surprising fact: so much of the volcanic activity in the Aleutians—a region noted for snow and ice cover, locally dense tundra vegetation, rapid surface change, and notoriously bad weather—is amenable to study with InSAR

Deformation of Aleutian Volcanoes is Common

Spatial variations in deformation patterns among various volcanoes Temporal changes in deformation behavior at individual volcanoes. Reflects the fact that Aleutian volcanoes span a broad range of eruptive styles,

sizes, magma compositions, and tectonic settings. Differing deformation patterns suggest differences in magma plumbing systems.

Deformation Styles are Diverse

Westdahl

Fisher

Shishaldin

Inflation of a few cm/year Subsidence of 1-2 cm/year No significant deformation

Unimak Island

(Lu et al., 2000, 2003, 2004) (Lu et al., 2007) (Lu et al., 2003; Moran et al., 2006)

5 km

Most frequently erupted volcanoes: erupt without deforming appreciably Seismicity extends to greater depths beneath individual volcanoes A large proportion of earthquakes deeper than about 10 km are low-frequency

events indicative of fluids Stratovolcanoes with symmetric cones Several interpretations:

no significant pre-eruptive and co-eruptive deformation was associated an eruption => Magma accumulation/transfer occur relatively quickly

Short-lived pre-eruptive inflation was balanced by co-eruptive deflation and no net displacement could be observed

The magma source is very shallow and magma strength is small so that deformation could only occur over the region of lost coherence.

Call for InSAR images with shorter time separations (a few days) and continuous GPS measurements near the summit to capture localized deformation if it exists.

A long list of volcanoes outside the Aleutian arc that fit into this category: Aracar, Copahue, Galeras, Irrupuntuncu, Llaima, Lascar, Nevado del Chillan, Nevado del Tolima, Ojos del Salado, Reventador, Sabancaya, Ubinas, and Villarica in the Andes; Dempo and Merapi in west Sunda; Bezymianny, Kliuchevskoi, and Sheveluch in Kamchatka, …

Open-conduit Volcanoes can Erupt Without Deforming

Insignificant co-eruptive deformation at frequently erupted stratovolcanoes

Shishaldin: 3rd most active volcano in Aleutians.

Moran et al., 2006

1993-1996 Image covering 1995 eruption

1998-1999 Image covering 1998 eruption

92-day ALOS interferogram spanning an eruption in 2007

10 km

7/27 – 10/27, 2007

Cleveland: The most active volcano in Aleutians since 1990s.

2011

0807

N

~100

m

Cleveland: An Eruption Episode

Lu and Dzurisin, 2014

Dome growth

2011

0818

N

~100

m



Dome growth

2011

0829

N

~100

m



Dome growth

2011

0909

N

~100

m



Dome growth

2011

0920

~100

m

N



Dome growth

2011

1001

~100

m

N



Dome growth

2011

1012

~100

m

N



Dome growth

2011

1023

~100

m

N



Dome growth

2011

1103

~100

m

N



Dome growth

2012

0108

~100

m

N


Explosion!

Ash


2012

0119

~100

m

N


Explosion!

Ash


2012

0210

~100

m

N


New dome!


Cleveland – a “open-vent” system

Episodic Intrusion - an intrinsic feature of Aleutian volcanism

At several Aleutian volcanoes, surface inflation occurs more or less continuously (albeit at time-varying rates) for periods of a few years or longer. Continuous process of magma formation, ascent, storage in the crust, and eruption.

Quasi-Continuous Deformation at Okmok Volcano

1997-1998

1998-1999 1999-2000 2000-2001 2001-2002 2002-2003

2003-2004

10 km

2005-2006 2004-2005

0 2.83 cm

1992-1993 1993-1995 1995-1996 1996-1997

Subsidence

Subsidence

1997 eruption

2006-2007

No deformation

0 28.3 cm

2007-2008

Minor inflation

Minor inflation



A larger percentage of Aleutian volcanoes inflate only episodically. Inflation associated with magma intrusion often is accompanied by seismic swarm. Intrusion process in other cases can be aseismic.

Episodic Intrusions Everywhere Along the Aleutians

6.32 Peulik:

6.37 Strandline Lake:6.36 Iliamna, Redoubt:

6.37 Spurr, Hayes:

6.21 Akutan:

6.28 Kupreanof:6.6 Tanaga:

6.20 Makushin:

6.10 Atka Volcanic Center:

Atka Volcanic Center



A larger percentage of Aleutian volcanoes inflate only episodically. Inflation associated with magma intrusion often is accompanied by seismic swarm. Intrusion process in other cases can be aseismic.

Factors that promote the progression of magmatic intrusions into eruptions include high gas content rapid gas exsolution a favorable stress environment (Moran and others, 2011).

Factors that can impede such progress include magma overpressure below some critical threshold (Pinel and Jaupart, 2004) high or increasing magma viscosity slow magma ascent non-favorable stress environment buffering effect of geothermal systems (Tait and others, 1989).

Some inflation episodes of Aleutian volcanoes did not happen overnight. Instead, they took weeks to several months. Often surface inflation episodes end before the associated earthquake swarms end; a

behavior that seems consistent with a stalled intrusion continuing to cause seismicity while strain is accommodated in the host rock.

The relatively slow pace of some intrusions, both in the Aleutians and elsewhere, might be a primary control on why they do not culminate in eruptions.

Most cases of broad surface uplift are attributed to magma intrusion Most of the model sources are located at or below 5 km BSL, deeper than

hydrothermal fluids are thought to exist in active volcanic environments (Fournier, 2007).

Numerical and conceptual models are simplistic and non-unique. Magmatic systems

are inherently complicated, involving physical and chemical interactions among tectonic strain, magma (itself a complex three-phase mixture of melt, crystals, and gas), groundwater, and heterogeneous host rock

Surface uplift can be caused by pressurization of a magma reservoir without

additional input of magma. Demanding for simultaneous geodetic and precise gravity measurements.

Nonetheless, the frequent occurrence of precursory uplift at volcanoes that eventually erupt and then subside in a similar pattern is strong circumstantial evidence for the existence of magma reservoirs that are supplied and replenished by intrusions from below, and which occasionally feed intrusions toward the surface.

A Deep Deformation Source Near a Volcano is not Synonymous With Magma, BUT …

Calderas in Aleutian: Young calderas in Aleutian: 10 Uplift and subsidence: 4 Persistent subsidence: 6

Floors of calderas underlain by

partly molten magma bodies, persist for hundreds of thousands of years, tend to move up or down with regularity.

Surface deformation is the norm

rather than an exception.

Caldera Systems Are Especially Dynamic

Aniakchak

Fisher 1-2 cm/year subsidence (source depth: 3-5 km)

1.5 cm/year subsidence (source depth: 3-5 km)

5 mm/year subsidence (source depth: ~7 km)

Emmons Lake

• Recent lava flows or pyroclastic flows Pattern of subsidence mimics the flow distribution The greatest amount of subsidence occurs where the flow is the thickest

• Hydrothermal-system depressurization as a result of cooling and fluid loss Subsidence fields do not correlate with the distributions of young flows Modeling suggests source depths in the range 0–4 km BSL

• Cooling and fluid loss from crustal magma reservoirs Subsidence sourced at greater depth than the other two types (~5–12 km BSL) Source locations for uplift and subsidence are essentially the same Some of the uplift episodes have culminated in eruptions

Surface Subsidence of Various Kinds is a Common Process at Aleutian Volcanoes

2 kmRec

hesh

noi V

olca

no

Observed deformation Inflation due to source at 5 km Subsidence to due

geothermal resources

=

Observed Modeled Residual

Okm

ok V

olca

no

InSAR Source Depth, Geochemistry, Seismicity

BD – Becharof discontinuity

Buurman et al., 2013 Lu and Dzurisin, 2014 Nye, 2008

Seis

mic

ity D

epth

(km

)

BD

Volcanoes from west to eat

• Structural influences on magma production rate, composition, and storage Lack of deep seismicity beneath the eastern part of the arc are due to a diminished flux of

magma through the crust relative to the more active central & western parts. Lesser magma flux results in longer magma residence times in the crust, more

fractionation and crustal assimilation, formation of more evolved magmas, and fewer eruptions

• Along-arc changes in stress regime

The horizontal compressional stress is oblique to the trend of arc over the eastern part of the arc perpendicular to the trend over the western part of the arc

Magma reservoirs tend to be deeper where regional horizontal compressional stress is greatest

• Differences between oceanic and continental parts of the arc

Magma rising beneath the arc would become neutrally buoyant and pond deeper in continental lithosphere than in denser oceanic lithosphere over the western Aleutian arc

• Along-arc variations in convergence rate, convergence angle, and

downdip velocity No correspondence with source depth

Tectonic and Structural Influences

Volcano Counts

Aleutian N. Andean

C. Andean

S. Andean

W. Sunda

# of Holocene volcanoes 97 35 69 63 84

# of historically active volcanoes

52 15 17 27 76

# of deformed volcanoes 31 2 4 7 7

# of magmatic deformation 24 1 3 5 6

# of surficial deformation 7 1 1 2 1

Lu, Z. and D. Dzurisin, 2014, “InSAR Imaging of Aleutian Volcanoes: Monitoring a Volcanic Arc from Space”, Springer Praxis Books, Geophysical Sciences, ISBN 978-3-642-00347-9, 390 pp.

Thank you!!! Questions: [email protected]

InSAR Imaging of Aleutian Volcanoes - ESA SEOMseom.esa.int/fringe2015/files/presentation117.pdf · InSAR Imaging of Aleutian Volcanoes ERS-1, ERS-2, JERS-1, Radarsat-1, Envisat, ALOS,

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