Comprehensive Risk Assessment for Natural Hazards - Planat

44
Hazard:* A threatening event, or the probability of occurrence
of a potentially damaging phenomenon within a given
time period and area.
Lahar:* A term originating in Indonesia, designating a debris
flow over the flank of a volcano.
Lava flow:* Molten rock which flows down-slope from a
volcanic vent, typically moving between a few metres to
several tens of kilometres per hour.
Magma:* The molten matter including liquid rock and gas
under pressure which may emerge from a volcanic vent.
Magma chamber:** An underground reservoir in which
magma is stored.
Mean return period:* The average time between occurrence of
a particular hazardous event.
Mitigation:* Measures taken in advance of a disaster aimed at
decreasing or eliminating its impact on society and environment.
Monitoring:* System that permits the continuous observation,
measurement and a valuation of the progress of a process
or phenomenon with a view to taking corrective
measures.
Mud flow:* The down-slope transfer of fine earth material
mixed with water.
Nuée ardente:* A classical expression for “Pyroclastic flow”.
Precursor:* Phenomena indicating a probable occurrence of an
earthquake or a volcanic eruption.
Prediction:* A statement of the expected time, place and
magnitude of a future event (for volcanic eruptions).
Prevention:* Encompasses activities designed to provide
permanent protection from disasters. It includes engineering
and other physical protective measures, and also
legislative measures controlling land use and urban planning.
Pyroclastic flow:* High-density flow of solid volcanic fragments
suspended in gas which flow downslope from a
volcanic vent (at speed up to 200 km/h) which may also
develop from partial collapse of a vertical eruption cone,
subdivided according to fragment composition and
nature of flowage into: ash flow, glowing avalanche, (“nuée
ardente”), pumice flow.
Repose time:** The interval between eruptions on an active
volcano.
Risk:* Expected losses (of lives, persons injured, property
damaged, and economic activity disrupted) due to a
particular hazard for a given area and reference period.
Based on mathematical calculations, risk is the product of
hazard and vulnerability.
Seismicity:* The distribution of earthquake in space and time.
Swarm: A series of minor earthquakes, none of which may be
identified as the mainshock, occurring in a limited area
and time.
Tephra: A general term for all fragmented volcanic material,
including blocks, pumice and volcanic ash. Fallout tephra
from eruption columns and clouds may be called airfall,
ash fall or tephra fall.
Tremor, harmonic:** Volcanic tremor that has a steady
frequency and amplitude.
Tremor, volcanic:** A continuous vibration of the ground,
detectable by seismographs, that is associated with
volcanic eruption and other subsurface volcanic activity.
Chapter 4 — Volcanic hazards
Viscosity:** A measure of resistance to flow in a liquid.
Volcanic eruption:* The discharge (aerially explosive) of
fragmentary ejecta, lava and gazes from a volcanic
vent.
Volcanic eruption index (VEI): Relative measure of the explosive
vigor of eruptions.VEI combines principally volume
of products and eruption cloud height. The scale ranges
from 0 to 8, the highest value.
Volcano:* The mountain formed by local accumulation of
volcanic materials around an erupting vent.
Vulnerability:* Degree of loss (from 0 to 100 per cent) resulting
from a potentially damaging phenomenon.
Zonation:* In general it is the subdivision of a geographical
entity (country, region, etc.) into homogenous sectors
with respect to certain criteria (for example, intensity of
the hazard, degree of risk, same overall protection against
a given hazard, etc.).
4.9 REFERENCES
Blaikies,P.,T.Cannon,I.Davis and B.Wisner,1994:At Risk,
Natural Hazards, People’s Vulnerability and Disasters.
Routledge, London and New-York, 284 pp.
Blong, R.J., 1984: Volcanics Hazards, a Sourcebook on the
Effects of Eruptions, Academic Press, 424 pp.
Bonham-Carter, G.F., 1994: Geographic Information
Systems for Geoscientists, Modeling with GIS.
Computer Methods in the Geosciences, Vol. 13,
Pergamon, 398 pp.
Cannon, T., 1994: Vulnerability Analysis and the Explanation
of “Natural” Disasters in Disasters, development and
environment, editors A.Varley, John Wiley and Sons Ltd.
CERESIS, 1989: Riesgo Volcánico, Evaluación y Mitigación en
América Latina, Aspectos Sociales, Institucionales y
Científicos, editor CERESIS, Lima, 298 pp.
Chouet, A.B., 1996: Long-period volcano seismicity: its
source and use in eruption forecasting, review article,
Nature, 380, pp. 309-316.
Crandell, D.R., 1973: Map showing potential hazards from
future eruptions of Mount Rainier, Washington (with
accompanying text), U.S. Geological Survey,
Miscellaneous geologic investigation, Map I-836.
Crandell, D.R., B. Booth, K. Kusumadinata, D.Shimozuru,
G.P.L. Walker and D. Westercamp, 1984: Source-book for
volcanic-hazards zonation, UNESCO, Paris, 97 pp.
Decker R.W. and B.B. Decker, 1992: Mountains of Fire;
the Nature of Volcanoes, Cambridge University Press,
198 pp.
Dvorak, J.J. and D. Dzurizin, 1997: Volcano Geodesy: The
Search for Magma Reservoir and the Formation of
Eruptive Vents,AGU, Reviews of Geophysics, 35, pp. 343-
384.
Ewert, J.W. and D.A. Swanson, 1992: Monitoring volcanoes:
Techniques and strategies used by the staff of the cascades
volcano observatory, 1980-90, U.S. Geological
Survey Bulletin, 1966, 223 pp.
Fisher, R.V. and G.A. Smith, 1991: Sedimentation in Volcanic
Settings, SEMP (Society for Sedimentary Geology),
Tulsa, Oklahoma, Special publication No 45, 257 pp.