Volcano Observatory Best Practice WorkshopVolcano Observatory Best Practice Workshop

Near Term Eruption ForecastingNear Term Eruption ForecastingErice, Sicily (IT), 11 - 15 September 2011Erice, Sicily (IT), 11 - 15 September 2011

CALDERASCALDERAS

Problems and challenges for near-term eruption forecastingProblems and challenges for near-term eruption forecasting

Paolo PapalePaolo Papale

INGV, ItalyINGV, Italy

• Caldera-forming eruptions are the largest eruptions on Earth. For Caldera-forming eruptions are the largest eruptions on Earth. For example, the Fish Canyon eruption in southwestern Colorado (United example, the Fish Canyon eruption in southwestern Colorado (United States) about 28 million years ago erupted more than 5,000 kmStates) about 28 million years ago erupted more than 5,000 km33 of of magma from La Garita caldera. That's enough magma to bury the entire magma from La Garita caldera. That's enough magma to bury the entire state of California to a depth of nearly 12 m! state of California to a depth of nearly 12 m!

• At least 1,299 episodes of unrest have occurred at 138 calderas greater At least 1,299 episodes of unrest have occurred at 138 calderas greater than 5 km in diameter during historical time. than 5 km in diameter during historical time.

• In a typical year some form of unrest (earthquakes, ground In a typical year some form of unrest (earthquakes, ground deformation, change in fumarole activity, or eruptions) occurs at about 18 deformation, change in fumarole activity, or eruptions) occurs at about 18 large calderas worldwide, and eruptions occur within or near at least five large calderas worldwide, and eruptions occur within or near at least five of them. of them.

source: http://volcanoes.usgs.gov/images/pglossary/caldera.phpsource: http://volcanoes.usgs.gov/images/pglossary/caldera.php

CALDERASCALDERAS: some general facts: some general facts

CALDERASCALDERAS: why are they different?: why are they different?

• The structure of calderas is profoundly different from The structure of calderas is profoundly different from that of stratovolcanoesthat of stratovolcanoes

• “ “negative” as opposed to “positive” edificenegative” as opposed to “positive” edifice• boarder faultsboarder faults• chaotic rock assemblagechaotic rock assemblage• development of large geothermal circulationdevelopment of large geothermal circulation• resurgencyresurgency• compressional/extensional portionscompressional/extensional portions• several distinct post-collapse ventsseveral distinct post-collapse vents• … …

CAMPI FLEGREI, CAMPI FLEGREI, Southern ItalySouthern Italy

main caldera bordermain caldera border

internal calderainternal caldera

post-collapse post-collapse eruptive ventseruptive vents

resurgent resurgent blockblock

extensional settingextensional setting

compressional settingcompressional setting

maximum maximum uplift area uplift area

extensive extensive degassingdegassing

CALDERASCALDERAS: why are they different?: why are they different?

They often display unrest dynamics that if observed at They often display unrest dynamics that if observed at central volcanoes, they would almost certainly culminate central volcanoes, they would almost certainly culminate into an eruptioninto an eruption

Observations that are often reported as “critical” for near-term Observations that are often reported as “critical” for near-term eruption forecast:eruption forecast:

• acceleration in seismicityacceleration in seismicity

• acceleration in deformation acceleration in deformation

• increase of gas fluxes, especially COincrease of gas fluxes, especially CO22 flux (and concentration) flux (and concentration)

(re: first two days of VOBP workshop)(re: first two days of VOBP workshop)

Are they equally diagnostic / critical at calderas?Are they equally diagnostic / critical at calderas?

CAMPI FLEGREICAMPI FLEGREI

Vertical displacement during last 2 centuriesVertical displacement during last 2 centuries

In 1983 about 40,000 people were evacuated from the town of Pozzuoli, In 1983 about 40,000 people were evacuated from the town of Pozzuoli, officially, due to the risk of structural collapses as a consequence of officially, due to the risk of structural collapses as a consequence of rapid ground displacement and seismic swarmsrapid ground displacement and seismic swarms

> 8,000 earthquakes recorded> 8,000 earthquakes recorded

3.5 m of ground 3.5 m of ground upliftuplift

FromFrom: Chiodini et al., 2008.: Chiodini et al., 2008.

Campi Flegrei, Italy, 1980-2008Campi Flegrei, Italy, 1980-2008

RABAUL eruption, 1994RABAUL eruption, 1994

““The eruption began on September 18 The eruption began on September 18 after less than a day of intense seismicityafter less than a day of intense seismicity…”…”

““The people who lived there were reminded of the inevitability of an eruption by The people who lived there were reminded of the inevitability of an eruption by intense intense earthquake activity and uplift of the ground within the caldera in the mid-1980'searthquake activity and uplift of the ground within the caldera in the mid-1980's.”.”

““However, despite warnings and a declared stage-2 emergency in 1983 and 1984, However, despite warnings and a declared stage-2 emergency in 1983 and 1984, Rabaul did not eruptRabaul did not erupt and, in fact, and, in fact, activity waned and remained at low levels until hours activity waned and remained at low levels until hours before the latest eruptionbefore the latest eruption broke out…” broke out…”

Source: http://hvo.wr.usgs.gov/volcanowatch/1994/94_09_23.htmlSource: http://hvo.wr.usgs.gov/volcanowatch/1994/94_09_23.html

Vent location is definitely more uncertain than for central volcanoes

CALDERASCALDERAS: why are they different?: why are they different?

map of the probability map of the probability of venting for a next of venting for a next eruption at Campi eruption at Campi FlegreiFlegrei

from from Selva et al., 2011Selva et al., 2011

5 km5 km

RABAUL, 1994: several vents up to km apart were activeRABAUL, 1994: several vents up to km apart were active

““At times on September 19, there may have been as many At times on September 19, there may have been as many as five active vents along the caldera rim, including as five active vents along the caldera rim, including several that began below the sea...”several that began below the sea...”

Source: http://hvo.wr.usgs.gov/volcanowatch/1994/94_09_23.htmlSource: http://hvo.wr.usgs.gov/volcanowatch/1994/94_09_23.html

CALDERASCALDERAS: why are they different?: why are they different?

Many caldera depressions are partially or totally filled with waterMany caldera depressions are partially or totally filled with water

Phreatic explosions and phreatomagmatic eruptions can be frequent at calderas

Geothermal circulation is usually well developed below caldera floorGeothermal circulation is usually well developed below caldera floor

CALDERAS: some “hot” questions

• what’s the origin of unrest at calderas, and why so often what’s the origin of unrest at calderas, and why so often large unrest dynamics do not culminate into an eruption?large unrest dynamics do not culminate into an eruption?

During last 3 decades a number of interpretations have been proposed for the During last 3 decades a number of interpretations have been proposed for the 1982-84 crisis at Campi Flegrei. Based on signal inversion and forward 1982-84 crisis at Campi Flegrei. Based on signal inversion and forward modeling, ground displacement has been alternately interpreted as mainly due modeling, ground displacement has been alternately interpreted as mainly due to:to:

• increased heat/fluid flow in the geothermal systemincreased heat/fluid flow in the geothermal system

• emplacement of a shallow magma bodyemplacement of a shallow magma body

High velocity – High Density

Inversion of P-wave velocity and gravity at Campi FlegreiInversion of P-wave velocity and gravity at Campi Flegrei

3D integrated v3D integrated vPP model of Campi Flegrei model of Campi Flegrei

From A. Zollo and co-workers

Seismic attentuation tomography

From De Siena et al., 2010

200-500 m200-500 m

200-

500

m20

0-50

0 m

0.1 0.1 kmkm33

From Di Vito and Orsi, 2009

Magnitude of last 5 ka activity at Campi FlegreiMagnitude of last 5 ka activity at Campi Flegrei

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

eruzione

volu

me

(DR

E)

volu

me

(D

RE

)

eruzione

volu

me

(km

3 D

RE

)

eruzione

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

eruzione

volu

me

(DR

E)

0.1 km3

0.25 km3

AD 1538 Monte NuovoAD 1538 Monte Nuovo

top of carbonatic basement

composition of the gas phase (wt% CO2)

pres

sure

(M

Pa) depth (km

)

Top of carbonatic basement

Seismic discontinuity

Vesuvius

0

100

200

300

400

500

0.0 0.2 0.4 0.6 0.8 1.0

Pre

ssur

e (M

Pa)

0

4

8

12

16

20

CO2 gas (wt fraction)

Dep

th (

km)

Minopoli 2

Agnano Monte Spina

Campanian Ignimbrite

Top of carbonatic basement

pres

sure

(M

Pa) depth (km

)

Seismic discontinuity

Campi Flegrei

composition of the gas phase (wt% CO2)

CO2 ~ 60 - 80 wt% in the gas phase

From Rutherford, this project and previous GNV Campi Flegrei ProjectFrom Rutherford, this project and previous GNV Campi Flegrei Project

Plinian phase D1 of the 4100 BP Plinian phase D1 of the 4100 BP Agnano Monte Spina eruptionAgnano Monte Spina eruption

1.5 – 3 km depth1.5 – 3 km depth

Agnano Monte Spina eruption

A few tens of hours before discharge

shallow phonolite

deep trachyte

From Rutherford, INGV-DPC Projects 2001-03/17 and 2004-06/V3_2From Rutherford, INGV-DPC Projects 2001-03/17 and 2004-06/V3_2

AVERNO AVERNO EruptionEruption

0,707265

0,707315

0,707365

0,707415

0,707465

0 1 2 3 4 5 6 7 8 9 10 11 12 13

87Sr

/86Sr

SM sp

SMs

SMc

Mond.15U3

Mond.152a2

w.r Mg-cpx. big Fe-cpx.small

Biot.

Magn.

glass Feld.frantz Apat

Feld. big

Mg-

Fe-cpx.big

Fe-cpx.int0,707265

0,707315

0,707365

0,707415

0,707465

0 1 2 3 4 5 6 7 8 9 10 11 12 13

87Sr

/86Sr

SM sp

SMs

SMc

Mond.15U3

Mond.152a2

w.r Mg-cpx. big Fe-cpx.small

Biot.

Magn.

glass Feld.frantz Apat

Feld. big

Mg-

Fe-cpx.big

Fe-cpx.int

IC EruptionIC Eruption

19.00

19.01

19.02

19.03

19.04

19.05

19.06206Pb/204Pb

0.70745 0.7075 0.70755 0.7076 0.70765

87Sr/86Sr

A1 wr E1 wr

E gray glass

AMS EruptionAMS Eruption

Chemical and isotopic evidence of mixing-mingling Chemical and isotopic evidence of mixing-mingling preceeding many CF eruptionspreceeding many CF eruptions

AMS EruptionAMS Eruption

From: From: Civetta, 2009Civetta, 2009

Schematic view of Campi Flegrei system in the past 5 ka.Schematic view of Campi Flegrei system in the past 5 ka.

heterogeneous, mostly shoshonitic, CO2-rich, large (>100 km3) magma reservoir

large geothermal circulationlarge geothermal circulation

CALDERASCALDERAS: some “hot” questions: some “hot” questions

• what’s the origin of unrest at calderas, and why so often what’s the origin of unrest at calderas, and why so often large unrest dynamics do not culminate into an eruption?large unrest dynamics do not culminate into an eruption?

• how to discriminate between unrest leading or not leading to how to discriminate between unrest leading or not leading to an eruption? (e.g., dominantly due to the action of magma vs. an eruption? (e.g., dominantly due to the action of magma vs. dominantly due to the action of geothermal fluids)dominantly due to the action of geothermal fluids)

• how to relate observations to expected vent location?how to relate observations to expected vent location?

• how to deal with often decades-long unrest dynamics?how to deal with often decades-long unrest dynamics?

• how long in advance will the signals allow robust forecast?how long in advance will the signals allow robust forecast?

• how to evaluate the hazard (and risk) related to often how to evaluate the hazard (and risk) related to often intense unrest dynamics?intense unrest dynamics?

Schematic view of Campi Flegrei system in the past 5 ka.Schematic view of Campi Flegrei system in the past 5 ka.

heterogeneous, mostly shoshonitic, CO2-rich, large (>100 km3) magma reservoir

large geothermal circulationlarge geothermal circulation

what controls the size of an eruption at calderas?what controls the size of an eruption at calderas?

or,or,

do we need large magma bodies at shallow depth for a new do we need large magma bodies at shallow depth for a new caldera-forming eruption?caldera-forming eruption?

More general interpretation issueMore general interpretation issue::

Whether unrest at calderas (e.g., Long Valley, Yellowstone, Whether unrest at calderas (e.g., Long Valley, Yellowstone, Campi Flegrei, …) simply punctuates long periods of quiet or is Campi Flegrei, …) simply punctuates long periods of quiet or is the early warning sign of future eruptions is an important but still the early warning sign of future eruptions is an important but still unanswered question unanswered question

Short-term volcanic hazard forecast at calderas is generally characterized by uncertainties

larger than for central volcanoes!

Boolean parameters are represented by “YES”

“Gray areas” correspond to variable probability of being in the adjacent states, depending on the measured values

ELICITATION V BACKGROUNDGray area

UNRESTGray area

MAGM. UNREST

Gray area

ERUPTION

VT (M > 0.8) [ev/day]   5   15                          

LP/VLP/ULP [ev/month]   2   10                          

Rate uplift [cm/month]   0.7   1.3                          

Uplift [cm]   2   6   6   15              T Pisciarelli     100   110                          VLP/ULP                 1   5              Deep VT (M > 0.8) [ev/day]               2   20              Deep LP (> 2 Km) [ev/day]               3   20              Disp. Hypocenters [km]                           1   3  Tremor                                     YESDeep Tremor (>3.5 Km)

                          YES            

Acc. seismic events                                       YESAcc. RSAM                                       YESNew fractures                                   YESMacr. (dm) variation in def.

                                    YES

Migr. max uplift                                       YESExt degassing               YES                        Magm. comp. gases                           YES            HF - HCl - SO2                         YES           YESPhreatic activity                                       YES

Red parameters: Seismicity

Green parameters: Deformation

Blue parameters: Geochemistry

Campi Flegrei – Pre-eruptive Event TreeCampi Flegrei – Pre-eruptive Event Tree

after Selva et after Selva et al., 2011al., 2011

DELPHI DELPHI METHODMETHOD

0.1

0

0.20.3

0.40.50.60.70.80.9

1

1981 1982 1983 1984 1985

unrest

magmatic

eruption

Application to Campi Flegrei crisis 1982-1984

after Selva et al., 2010after Selva et al., 2010

Probability estimates: beyond the color codesProbability estimates: beyond the color codes

Colour codeColour code Continuous Continuous probabilities (with probabilities (with

uncertainties)uncertainties)Green: normal

Yellow: watch

Orange: attention

Red: crisis

Artificial discretization forces Artificial discretization forces actions to be strictly tied to actions to be strictly tied to evaluation from scientistsevaluation from scientists

Scientists become Scientists become de-factode-facto decision-makersdecision-makers

Correctly communicate the Correctly communicate the uncertain nature of predictionsuncertain nature of predictions

Allow a clear distinction of roles Allow a clear distinction of roles and responsibilities between and responsibilities between

scientists and decision-makersscientists and decision-makers

GLOBAL GLOBAL VOLCANO VOLCANO MODEL(S)MODEL(S)

after Longo et after Longo et al., 2010al., 2010

vert

ical

dis

plac

emen

t (m

)

0 2 4 6time (hours)

afterafter Voight et al., Voight et al., 20062006

ULP ground oscillations