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NVEWS
National Volcano
Early Warning System
(Tables adapted from:
PDF by John Ewert, USGS Open-File Report 2005-11644)
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List of the 15 hazard and 10
exposure factors used in the NVEWS threat
assessment and their scoring ranges. |
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Hazard Factors
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Scoring Ranges
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Volcano type |
0
or 1 |
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Maximum Volcanic Explosivity Index
|
0
to 3 |
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Explosive activity in past 500 years?
|
0
or 1 |
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Major explosive activity in past 5000 years?
|
0
or 1 |
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Eruption recurrence |
0
to 4 |
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Holocene pyroclastic flows?
|
0
or 1 |
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Holocene lahars? |
0
or 1 |
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Holocene lava flow? |
0
or 1 |
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Hydrothermal explosion potential?
|
0
or 1 |
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Holocene tsunami? |
0
or 1 |
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Sector collapse potential?
|
0
or 1 |
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Primary lahar source? |
0
or 1 |
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Observed seismic activity
|
0
or 1 |
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Observed ground deformation
|
0
or 1 |
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Observed fumarolic or magmatic degassing
|
0
or 1 |
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Total of Hazard Factors
|
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Exposure Factors |
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Log10
of Volcano Population Index (VPI)
at 30 km |
0
to 5.4 |
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Log10
of approximate population
downstream or downslope |
0
to 5.1 |
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Historical fatalities? |
0
or 1 |
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Historical evacuations? |
0
or 1 |
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Local aviation exposure |
0
to 2 |
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Regional aviation exposure
|
0
to 5.15 |
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Power infrastructure |
0
or 1 |
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Transportation infrastructure
|
0
or 1 |
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Major development or sensitive areas
|
0
or 1 |
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Volcano is a significant part of a populated
island |
0
or 1 |
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Total of Exposure Factors
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Sum of all hazard factors X
Sum of all exposure factors = Relative
Threat Ranking |
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Hazard and exposure factors
used in threat assessment of U.S. volcanoes
for the National Volcano Early Warning
System.
(factors pertaining to
Augustine are in bold type) |
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Hazards Factors
|
|
Score |
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Volcano type
If
volcano type is cinder cone, basaltic field,
small shield, or fissure vents: Score = 0
If
volcano type is stratocone, lava domes,
complex volcano, maar or caldera: Score = 1
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1 |
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Maximum Volcano Explosivity Index (VEI)
If
maximum known VEI ≤ 2: Score = 0
If
maximum known VEI = 3 or 4: Score = 1
If
maximum known VEI = 5 or 6: Score = 2
If
maximum known VEI ≥ 7: Score =
3
If
no maximum VEI is listed by GVP and if
volcano type = 0: Score = 0
If
no maximum VEI is listed by GVP but volcano
type = 1: Score = 1
If
no known Holocene eruptions and the volcano
is not a silicic caldera system:
Score = 0 |
1 |
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Explosive activity
If
explosive activity (VEI ≥ 3) within the last
500 years: Score = 1
|
1 |
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Major explosive activity
If
major explosive activity (VEI ≥ 4) within
last 5000 years: Score = 1
|
1 |
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Eruption recurrence
If
eruption interval is 1-99 years: Score = 4
If
eruption interval is 100 – 1,000 years:
Score = 3
If
eruption interval is 1,000 to several
thousand years: Score =2
If
eruption interval is 5,000-10,000 years, or
if no Holocene eruptions but it is a
large-volume restless silicic system that
has erupted in the last 100,000 years: Score
= 1
If
no known Holocene eruption: Score = 0
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4 |
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Holocene pyroclastic flows?
If
yes: Score = 1
|
1 |
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Holocene lava flows?
If
Holocene lava flows have traveled beyond the
immediate eruption site or flanks and
reached populated areas: Score =1
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0 |
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Holocene lahars?
If
Holocene lahars have traveled beyond the
flanks and reached populated areas: Score =1
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0 |
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Holocene tsunami(s)?
Has it produced a tsunami within the
Holocene? If yes: Score = 1
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1 |
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Hydrothermal explosion potential?
If
the volcano has had Holocene phreatic
explosive activity, and/or the volcano has
thermal features that are extensive enough
to pose a potential for explosive activity:
Score =1
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1 |
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Sector collapse potential?
If
the volcano has produced a sector collapse
in Quaternary-Holocene time and has
re-built its edifice, or, has high
relief, steep flanks and demonstrated or
inferred alteration: Score = 1
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16 |
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Primary lahar source?
If
volcano has a source of permanent water/ice
on edifice, water volume > 106
m3:
Score = 1
|
0 |
Historical Unrest Factors
|
Score
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Observed seismic unrest
Since the last eruption, in the absence of
eruptive activity, within 20 km of the volcanic
edifice? If yes: Score = 1
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1
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Observed ground deformation
Since the last eruption, in the absence of
eruptive activity, inflation or other evidence
of magma injection? If yes: Score = 1
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0 |
Observed fumarolic or magmatic degassing
Since the last eruption, in the absence of
eruptive activity, either heat source or
magmatic gases? If yes: Score = 1
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0 |
Total of Hazard Factors
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13
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Exposure Factors
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Log10
of Volcano Population Index (VPI)
at 30 km
Calculated with LandScan population database.
Visitor statistics for volcanoes in National
Parks and other destination recreation areas are
added to the VPI factor where available.
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0 |
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Log10
of approximate population
downstream or downslope
Population outside the 30 km VPI circle included
within the extent of Holocene flow deposits or
reasonable inundation modeling. This factor to
be used only with volcanoes that have a primary
lahar hazard (e.g. Cascade stratovolcanoes) or
significant lava flow hazard (e.g. Mauna Loa).
|
0 |
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Historical evacuations?
If
yes, and a permanent population is still
present: Score = 1
|
0 |
Local aviation exposure
If
any type volcano is within 50 km of a
jet-service airport, score = 1; if a Type 1
volcano is within 300 km of a jet-service
airport, score = 1; if a Type 1 volcano
is within 300 km of a major international
airport, score = 2; if none of these criteria
are met, score = 0. |
2 |
Regional aviation exposure
This score is based on the log10
of approximate daily passenger
traffic in each region. At present, in the U.S.,
this score ranges from 4 to 5.15. The regional
risk code is applied only to type 1
volcanoes and those type 0 volcanoes that
have produced explosive eruptions. |
4.15 |
Power infrastructure
Is
there power infrastructure (e.g., power
generation/transmission/distribution for
electricity, oil, or gas) within flowage hazard
zones, or in an area frequently downwind of the
volcano and close enough to considered at some
risk? If yes, score =1 |
0 |
Transportation infrastructure
Is
there transportation infrastructure (e.g., port
facilities, rail lines, major roads) within
flowage hazard zones, or in an area frequently
downwind of the volcano and close enough to
considered at some risk? If yes, score = 1
(Augustine poses a major risk to any air or sea
traffic in the area, and tsunamis/ash pose a
hazard to facilities near the coast.3) |
1
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Major development or sensitive areas
Are there major developments or sensitive areas
threatened (e.g., National Park facilities,
flood control projects, government facilities,
developed tourist/recreation facilities,
manufacturing or other significant economic
activity)? If yes, score =1 |
0 |
Volcano is a significant part of a populated
island
Holocene volcanic deposits cover >25% of land
mass. If yes, score = 1
|
0 |
Total of Exposure Factors
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7.1
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Sum of all hazard factors x Sum of all exposure
factors = Relative Threat Ranking
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92.3
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Based
upon the scheme developed by the USGS, Mt. Augustine is
monitored at Level 3,4 as there are 11
seismic monitoring stations on the island alone, with
the ability to track deformation and gas emissions;
Satellite imaging is used regularly to monitor any sort
of thermal activity that may indicate an eruption.10
When Augustine's Relative
Threat Ranking - 92.3 - is compared to the threat
rankings of other volcanoes, it is found that it should
be monitored at Level 4,4 thus there
is a monitoring gap of 1.
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