Monitoring and risk assessment Flashcards
91% of fatalities [4]
pyroclastic flows, lahars, tsunamis, famine and disease
Long term forecasting [2[
identify high risk
hazard mapping
Shote term forecasting [3]
real-time monitoring, eruption forecasting and prediction, emergency plans and management
Identifying high risk volcanoes [4]
past eruptive history, prevalence of explosive eruptions, evidence of seismic activity, proximity to population
Volcano monitoring [2]
seismic monitoring, ground deformation
Eruption forecasting [5]
microgravity, magnetic field, volcanic gases, temp, hydrology
Volcanic seismic monitoring
preceded by earth tremors, fluid movement causing rocks to crack (low freq EQ), breaking rocks causing high-freq EQs,
Volcanic EQs [2]
mag 2/3, 10km below surface
Seismic monitoring [4]
timing, location, depth and magnitude
Tremors of short periods
high frequency, active intrusion of magma chamber
Harmonic tremors
continuous vibration from magma flowing through feeder conduits
Ground deformation e.g. Kilauea
Inflation (gradual) or deflation (sudden)
Ground deformation monitoring techniques [5]
Geoditic levelling cGPS Tiltmeter InSAR EDM
Geoditic levelling
measures elevation differences, repeat to measure change over time
cont. GPS
stable monuments with geodetic grade antenna and GPS receiver. M accuracy in standalone
Inflation monitoring using GPS
Mauna Loa
Tiltmeter, e.g. Kilauea
1-2cm displacement
Interferometric Synthetic Aperture
Phase shift - ground uplift = less distance of satellite. Line of Sight change
Electronic Distance Meter
electromagnetic signal. short to medium range (10-50km) 5mm short range accuracy
Micro gravity
used with precise levelling, gravity decrease implies loss of mass
Changes in loca Magnetic field
Molten = non-magnetic
Magnetite crystals magnetised below 500 degrees/Currie Point
Host e.g. Basalt = magnetic (negative anomaly)
Volcanic gas monitoring
Direct measurements on ground, airborne or analysis of water chemistry
Discharge rate of Mt St Helens gases and composition
seismic ^
dome ^
tilt ^
SO2 ^
Discharge rate SO2 CO2
SO2 increase preceding
CO2 first to exsolve from magma
Thermal monitoring
Differentiate hot from cold eruptive events
Hydrology
Monitoring sediment erosion/transport/deposition
water temp
ground vibrations
Hazard maps
Previous eruption freq, areas under threat. 50-80km away.
