Hazard vs' Risk

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Volcanic Hazards

• Hazard vs. Risk ??
• hazard the probability of an area being affected
  by destructive volcanic processes in a given time
• volcanic hazard volcanic activity that endangers
  the lives of people and property both close to
  and far away from a volcano
• activity involves the explosive ejection or
  flowage of rock fragments and molten rock
• can be hot or cold, wet or dry, and fast or slow
• risk the possibility of loss (life, property,
  economy, etc.) due to a hazard

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Volcanic Hazards

• Hazard vs. Risk ??
• Risk (value) x (vulnerability) x (hazard)
• where,
• value number of lives, property value, economic
  capacity
• vulnerability 0-100 of the value lost in an
  event
• hazard (0-100 damaging capacity) x (hazard
  frequency)
• so, the risk is much greater if there are
  numerous small towns built in valleys surrounding
  a moderately active volcano (such as S. America
  or Indonesia)
• versus the risk of caldera eruption occurring in
  a remote region

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Volcanic Hazards

• Importance
• volcanic disasters occur less frequently, affect
  fewer people, and produce less loss than other
  natural disasters
• about 1500 active volcanoes globally with the
  ability to affect 10 of the worlds population
  (local to regional hazards)
• compare this to 40 living near major
  earthquake faults or 60 vulnerable to flood or
  drought
• example deadliest disasters
• volcano Tambora, Indonesia (1815) 92,000
• hurricane Bangladesh (1970) 500,000
• Earthquake China (1556) 820,000 (1976)
  800,000
• in the US, you are far more likely to be hit by
  lightning than be affected by a volcanic hazard
• however, in Japan Indonesia, chances are 20-50
  times greater

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Volcanic Hazards

• Statistics are commonly misleading
• no reliable data gathering agency for these
  disasters
• official government reports can be wrong
• example China reports only 240,000 dead in the
  1976 earthquake
• volcanic-related deaths by region (1600 - 1995)
• Indonesia 165,000
• Caribbean 31,000
• S. America 26,000
• Japan 21,000
• Iceland 10,000
• Others 20,000
• large singular events (Krakatau, Tambora,
  Pelee, Ruiz)

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Volcanic Hazards

• Statistics by hazard
• Hazard (1600 - 1900) (1900 - 1990)
• Lava-flow 985 85
• Ash-fall 11,500 3,100
• PDC 55,000 37,000
• Tsunami 44,000 500
• Lahar 30,000 23,500
• Disease 95,000 3,100
• Gas 2,000 1,700

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Volcanic Hazards

• Process of Hazard Assessment
• Mitigation versus Monitoring
• monitoring the regular collection of data
  sources in order to assess a volcanos activity
  state
• mitigation activities/processes/procedures
  designed to reduce and/or eliminate the threat of
  the hazard

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Volcanic Hazards

• Process of Hazard Assessment
• fundamental research is the first step!
• literature search/history geologic and
  stratigraphic mapping geochemical analyses of
  rock and gas samples geophysical surveys
• ideally done before activity initiates
• example first done systematically at Mt. St.
  Helens in the late 1970s
• report came out less than a year before the May,
  1980 eruption
• was critical when it came to dealing with the
  what if questions
• history now exists for all the Cascade volcanoes,
  but many dangerous
• volcanoes still have very little data (incl
  monitoring)

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Volcanic Hazards

• USGS Volcanic Hazards Diagram
• shows many of the primary volcanic hazards
  associated with an eruption
• http//volcanoes.usgs.gov/ Hazards/What/hazards.ht
  ml

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Volcanic Hazards

• Primary volcanic hazards
• Ash Falls
• Pyroclastic Density Currents (PDCs)
• Mudflows (lahars)
• Volcanic Landslides
• Volcanic Tsunamis
• Lava Flows
• Poisonous Gas

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Volcanic Hazards

• Ash Falls
• can cover large areas for days to weeks
• ash will last on the ground for months to years
• making land and water unusable
• provide material for future hazards (lahars)

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Volcanic Hazards

• PDCs
• due to collapse of eruption column or lava dome
• Large ones often comprised of two parts
• Basal surge (denser, "hugs" topography)
• convecting cloud (less dense, can ignore
  topography)
• travel gt 100 mph with temperatures of 100 - 600
  degrees C

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Lava Flows/Domes
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Volcanic Hazards

• Mudflows (lahars)
• due to excessive rain mobilizing ash and rock
  and/or melting of snow and glacial ice
• produces rivers of mud and debris that can affect
  great distances
• slow to very fast moving
• speed is a function of the bulk viscosity and
  slope etc

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Volcanic Hazards

• Volcanic Landslides
• large mass-movements of rock and debris from a
  volcano
• due to an eruption or simple failure of weak
  structures (hydrothermal alteration is often
  important)
• can cause great devastation due to high speeds
  and bulk density of the material

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Volcanic Hazards

• Volcanic Tsunamis
• commonly called tidal waves
• caused by quakes and volcanic eruptions
• PDCs and/or landslides entering the water
• can affect people thousands of miles away if they
  are large enough

Hilo, HI (1946)
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Volcanic Hazards

• Lava Flows
• not generally hazardous or life threatening
• can cause large amounts of property damage and
  affect commerce

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Volcanic Hazards

• Poisonous Gas
• mostly an irritant, however it can be quite
  deadly
• common gas species H2O, CO2, CO, SO2, H2, HF
• volcanic fog (VOG) in Hawaii H2SO4
• can cause crop/land/water damage
• CO2 collects in low-lying areas, heavier than air

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Monitoring/Mitigation

• volcanic monitoring
• different types (several of which are
  interrelated)
• Deformation
• Seismic
• Heat Discharge
• Gas Discharge
• Water Flows

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Monitoring/Mitigation

• Deformation
• measurement of changes in the volcano's shape due
  to increasing pressures and/or the presence of
  new magma
• tilt meters
• highly sensitive water filled tubes many meters
  long (old) and electronic systems (new)
• can detect changes in slope as small as 1mm over
  1km distance
• one of the oldest techniques

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Monitoring/Mitigation
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Monitoring/Mitigation

• Deformation
• laser sighting
• precise measurements of the distance between a
  laser base station and a reflective target
• targets are placed on the volcano and
  observations are made from the safety of the
  volcano observatory
• global positioning system (GPS)
• uses satellite broadcasts and triangulation to
  precisely locate the receiver's location and
  elevation
• a series of GPS receivers on a volcano can record
  very small changes in inflation and lateral
  movement

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Monitoring/Mitigation

• Deformation
• radar interferometry
• newest technique that uses radar signals beamed
  from satellites to measure the distance between
  the satellite and the volcano
• need two or more observations to tell if the
  there has been movement

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Monitoring/Mitigation

• Seismic Monitoring
• network of seismometers to measure the magnitude
  (M), frequency (F) and distribution (position) of
  earthquakes under an active volcano
• Types??
• high-frequency quakes
• volcanic tremor
• Aseismic zone

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Monitoring/Mitigation

• Seismicity Types
• high-frequency quakes
• caused by rock fracture above a magma body
• brittle strain, therefore these occur at shallow
  depths (0-3 km)
• generally small M and high F
• volcanic tremor
• caused by magma movement in the conduit as well
  as the formation of gas bubbles in the magma
• causes long-period quakes
• lower depth than high-frequency quakes
• Aseismic zone
• region of no quakes
• defines a potential magma (liquid) storage area

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Monitoring/Mitigation
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Monitoring/Mitigation
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Monitoring/Mitigation

• Heat Flow
• volcanoes can begin to heat up weeks to days
  before an eruption
• soil and water (groundwater and surface water)
  temperatures can be monitored
• direct measurement
• using probes
• can be dangerous for the volcanologist
• indirect measurements
• radiant heat can be measured from a distance
• using a more sensitive device flown in an
  aircraft or a satellite
• using a hand-held device (radiometer) for small
  distances (lt 2km)

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Monitoring/Mitigation
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Monitoring

• Heat Flow
• indirect measurements
• radiant heat can be measured from a distance
• using a hand-held device (radiometer) for small
  distances (lt 2km)
• well developed channels with tube formation high
  on the shield

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Monitoring/Mitigation

• Volcanic Gas Monitoring
• chemistry of the emitted volcanic gas can be used
  to determine the composition of the magma and the
  likelihood of an eruption
• can be direct sampling or indirect measurements
• How??
• direct sampling
• indirect sampling

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Monitoring/Mitigation

• Volcanic Gas Monitoring
• direct sampling
• volcanologists capture gases emitted from vents,
  fumaroles, lakes and soil
• can be very dangerous
• indirect sampling
• satellite, plane and ground measurements
• certain gases are easily detectable (SO2, H2, HF)
  
• others are not (H2O, CO2, CO)
• example correlation spectrometer (COSPEC) is
  used to detect SO2
• looking at light in the UV (SO2 is easy to detect
  in that region)
• COSPEC can be mounted on a plane, helicopter or
  vehicle or positioned on the ground

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Monitoring/Mitigation
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Monitoring/Mitigation

• Hydrologic Monitoring
• lahar hazards (days - months)
• long-term threat of sediment transport/erosion
  and increased flooding (months - years)
• How??
• direct sampling
• stream gauges
• mapping
• indirect sampling
• acoustic-flow monitor (AFM) stations
• rainfall meters

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Monitoring/Mitigation
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Monitoring/Mitigation

• Mitigation
• activities, processes or procedures designed to
  reduce and/or eliminate the threats of volcanic
  hazards
• important to remember that mitigation is
  different than monitoring
• however, monitoring is necessary for eventual
  mitigation
• Different Categories
• physical structures/effort
• public education
• use of new technologies

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Monitoring/Mitigation

• Physical Structures
• Lava Diversion
• use of permanent or temporary structures to keep
  the lava from advancing into a town or structure
• works because of the slow moving nature of most
  lava flows
• only is effect sometimes and then only on a small
  scale
• large, fast flows will quickly overtop any
  man-made structure
• used successfully in the 1983 eruption of Mt.
  Etna
• within a month the flow was 6.5 km long
  threatening 3 towns
• rubble barrier about 10 m high, 30 m wide 400 m
  long
• eventually worked!
• total cost 3 million (potentially saved
  5-25 million)

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Monitoring/Mitigation
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Monitoring/Mitigation
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Monitoring/Mitigation

• Physical Structures
• Lahar Diversion
• Sabo Dams dams constructed in river valleys
  which are designed to
• strain out large debris
• divert lahar away from people/property
• minimize erosion
• common in Japan and Indonesia
• where large populations live and work near/in the
  threatened river valleys

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Monitoring/Mitigation
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Monitoring/Mitigation
Merapi Volcano, Indonesia
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Monitoring/Mitigation

• Physical Structures
• Water Cooling
• rapid cooling of the flow front using cold water
  in order to strengthen the lava and form a
  natural blockage
• used in Iceland in 1973 to try to stop a flow
  from Heimaey Volcano from closing off an
  important harbor
• sprayed seawater for days on flow
• many scientists are convinced that the flow was
  stopping and that the water did very little

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Monitoring/Mitigation

• Public Education
• can be critical in reduction of the risks
• needed in third world countries
• population is high
• information dissemination is low
• needed also in first world countries
• recurrence interval is large
• perceived threat from volcanoes is minimal

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Monitoring/Mitigation

• Public Education
• begin training early
• Japan does this for grade school kids living in
  hazard-prone areas
• continue public education/drills/training in
  those areas
• especially before and during a hazard
• increase funding for monitoring at hazardous
  volcanoes
• eventually produce a geologic and hazards map for
  the volcano and the surrounding areas
• have the local towns integrate those reports into
  their operating plan

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Monitoring/Mitigation

• New Technologies
• remote sensing/detection newer and newer
  satellite instruments are providing better
  detection
• increased resolution and quicker coverage, which
  are all important for hazard mitigation
• robotics and ground-based sensors are providing
  needed data without endangering the lives of the
  volcanologists
• warning systems are being established
• lahar "detectors" combinations of seismometers
  and rain gauges which radio warnings back to a
  central point when they detect both high rainfall
  and the seismic energy associated with a moving
  lahar
• tsunami systems warning sirens set off when an
  quake or eruption is detected