Hazard
- probability that a specific damaging event will take place within a particular period of time
- events are not a hazard but become so because of human use of land
Risk
- probability of a hazardous event and the expected damage if the event does occur
Catastrophe
- massive disaster that requires significant expenditure of money and a long time (years) for recovery to take place - Hurricane Katrina
Disaster
- hazardous event that occurs over a limited time span in a defined area
- criteria: (1) 10+ people killed (2) 100+ people affected (3) state of emergency declared (4) emergency assistance is required
- if 1 occurs it is a natural disaster
Main Impacts
- loss of life
- damage to infrastructure (transportation, health services, residences)
Vulnerability
- attributes, activities and aspects of a person/community that increases their susceptibility to given dangers
6 Forms of Vulnerability
- exposure to dangerous agents and environments
- weakness - predisposition of persons, buildings, communities or activities to greater harm
- lack of protection
- lack of resources to affect risks or respond to danger
- no capability to avoid/withstand or offset and recover from disaster
- inability to influence safety conditions or acquire protection and relief
Resilience
- measurement of vulnerability and how quickly a community can recover from disaster
Direct Effect
- people killed, injured, dislocated or otherwise damaged by a particular event
- felt by fewer people
Indirect Effect
- responses to the disaster (emotional distress, donation of money or goods, paying of taxes levied to finance recovery)
- felt by many people
Prediction
- specifies date, time and size of event
Forecast
- has ranges of certainty (i.e. weather)
Probability of Occurrence
determining the probability of an event in a particular location within a time span
Precursor Events
- hazardous events are preceded by precursor events
o i.e. surface of ground may creep prior to landslide
o Identification of precursor event help predict when and where a major event is likely to happen
Warning
- after a hazardous event has been predicted or forecast has been made, public must be warned
Magnitude vs. Frequence
- Magnitude: function of the amount of energy released
- Frequency: the interval between occurrences
Structural Adjustment
- design of better building material and structural design that reduces the impact on the structure
- more for floods and landslides
Non-Structural Adjustment
- legislation, planning, insurance, education, warnings
Faults
- fracture where rocks have been displaced
Descriptors
- Indicate the location of the fault line and point at which the quake originated: o Point of origin o Focus o Hypocenter o Epicenter
Seismic Waves
- Main determinant of earthquake hazard is the land waves generated from force of rupture
- Travel through land and at surface causing shaking of the ground
Reservoirs
- Dams enable communities to survive in regions where water resources are limited
- Essential in drought prone regions to provide water for agricultural irrigation and human consumptions
Deep Waste Disposal
- The disposal of unwanted liquids into bedrock has been linked to earthquake activity at a number of sites
- Liquid increases fluid pressure and causes slippage and fractures in bed rock
Pumping of Oil and Gas
- Removal of liquid and gases from bedrock can trigger quake activity (Alberta, BC)
Hydraulic Fracturing
- “Fracking” is cause of earthquake in regions of oil and gas productions
Divergent Boundaries
- A linear feature that exists between two tectonic plates that are moving away from each other.
Convergent Boundaries/Subduction Zone
- Also known as a destructive plate boundary (because of subduction), is an actively deforming region where two tectonic plates move together and collide
Transform Boundaries
- A fault whose relative motion is horizontal
Type of Faults
Strike-slip: horizontal displacement of fault plane
Thrust: hanging wall moves up and over footwall
Normal: footwall moves up and hanging wall moves down (opposite movement is called reverse fault)
Richter Scale
- based on a scale of 10
- The readings help determine the level of magnitude of an earthquake
- Derived from the logarithm of the amplitude of waves, recorded by a seismograph
Mercalli Scale
- focuses more on impact to society (# deaths, buildings collapsed)
- 3 WEAK: Felt by nearly everyone; some damage to wall plaster; unstable objects are overturned
- 4 WEAK: Felt on upper floors of buildings; stationary cars may rock slightly; vibration feels like the passing of a truck
- 8 SEVERE: Few masonry structures remain standing; bridges are destroyed; landslides are common
- 2 WEAK: Felt by very few people
Primary Hazards
- Primary damage that occurs is related to shaking of the ground and subsequent failure of structures (injuries and death)
Secondary Hazards
- liquefaction
- landslides
- land level changes
- tsunami
Tertiary Hazards
- When the initial hazard lead to the initiation of other hazards not always directly associated with the initial hazard
- fire, flood, exposure, disease, stress
Conditions that Create Vulnerability
- construction material (quality, availability and cost)
- building design (doors, windows, roof lines, room layout)
- upkeep and renovations (improve structural strength)
- site and situations (stability of foundations and closeness to slopes and other structures)
Short Term Predictions
Make predictions by observing:
- Foreshocks: tracking the rate of small shocks it is possible an increase in activity will provide warning of a larger earthquake
- Patterns and frequency of earthquakes and foreshocks
- Deformation of the ground surface including uplift and subsidence
- Seismic gaps along faults where there are sites of inactivity
- Geophysical and geochemical changes in groundwater levels, temperatures, soil and water chemistry
Tephra
the material explosively released during volcanic activity
Types of Volcanos
- Stratovolcano or Composite Volcano
- Shield Volcano
- Volcanic Domes
- Cinder Cones
Humans & Volcanos
- One of the few hazards we study that have little evidence of human activity affecting them.
- The level of human activity required to create a volcano is not often reached intentionally or unintentionally.
Benefits of Volcanos to ecosystem
- Volcanic soil (create rich soils attractive to farming)
- Geothermal power (alternative energy source, mining heat from earth)
- recreation (tourism attractions)
Volcanic Explosivity Index (VEI)
- measure of the volume of material erupted and the height of the ash plume.
- starts at 0 and no upper limit exists
Pillow Lava Flow
- occurs when hot lava flows into water and cools rapidly, creating long tubes and bulbous pillow-shaped mounds of rock.
Pahoehoe Lava Flow
characterized by a smooth, billowy, or ropy surface, ropy surface develops when a thin skin of cooler lava at the surface of the flow is pushed into folds by the faster moving, fluid lava just below the surface, flows tend to be relatively thin, from a few inches to a few feet thick
AA Lava Flow
Characterized by a rough, jagged surface, flows advance much like a bulldozer
Ash Fall
- Fine-grained fragmented debris, ash and abrasive volcanic glass
- Large eruptions cover property and can cause breathing problems and plane crashes.
Pyroclastic Flow
- Explosive volcanoes produce an incinerating mixture of gas and debris measuring between 700°-1000°C called pyroclastic flow.
- This fast-moving (150 km/h) flow burns everything in its path as it moves down the flank of the volcano.
- The flow can erupt vertically or from the side, which is a more deadly, concentrated flow.
Lahar - Volcanic Mudflow
- mixture of water and debris from the volcano
- The hazard of lahar is related to moisture conditions - greater moisture content will have a higher velocity and lower viscosity
Poisonous Gases
- main component of poisonous gases is water vapour (CO2, CO)
- Other gases, such as hydrogen sulfide (H2S), sulphuric acid (H2SO4) and hydrochloric acid (HCl) are created which cause acid rain and burning in humans and vegetation
Methods to Identify Possible Volcanic Activity
- Ground Deformation - Land Surface Monitoring
- Seismicity
- Remote Sensing
- Volcanic Gases
- Geologic History
- Hydrologic Hazards
Alert: Normal/Green
Non-erupting volcano is exhibiting typical background activity (including steaming, seismic events, thermal feature, or degassing)
Alert: Advisory/Yellow
Volcano is exhibiting signs of elevated unrest above known background activity.
Alert: Watch/Orange
Volcano is exhibiting escalating unrest with increased potential of eruption, timeframe uncertain OR an eruption is underway that poses limited hazards including no or minor volcanic-ash emissions.
Alert: Warning/Orange
Major volcanic eruption is imminent, underway, or suspected but it poses limited hazards to aviation because of no or minor volcanic-ash emissions
Alert: Watch/Red
Volcanic eruption is underway that poses limited hazards to ground-based communities but includes significant emission of ash into the atmosphere that could affect aviation
Alert: Warning/Red
Major volcanic eruption is imminent, underway, or suspected with hazardous activity both on the ground and in the air.
Tsunamis
A long high sea wave caused by an earthquake, submarine landslide, or other disturbance
Mega-tsunami
Produced by asteroid impact; wave that is about 100 times higher than the largest tsunami produced by an earthquake
2 ways that earthquakes can cause a tsunami
- Movement of the seafloor
2. Triggering a landslide
Distant/Tele-tsunami
Travels out across the deep ocean at high speed
Travels at least 1000 km before reaching land
Local tsunami
Heads towards land , can arrive quickly following an earthquake
Characteristics of regions at risk of tsunamis
Geographic location of a cost in relation to potential tsunami sources; earthquakes, landslides, volcanos
Rogue wave
Waves that are greater than twice the size of surrounding wave and are very unpredictable
Storm surge
A rising of the sea as a result of atmospheric pressure changes and wind associated with a storm
3 main processes that lead to displacement of water
- Earthquake must register at least a 7 on the Richter scale
- Seabed must be lifted or lowered by the earthquake
- Epicentre of earthquake must be near to the earth’s surface
4 stages of tsunamis
Stage One: Earthquake rupture in the seafloor pushes water upwards
Stage Two: Tsunami moves rapidly in deep ocean, reaching speeds of 950km/hr
Stage Three: As the tsunami nears land it slows to about 45km/hr but is squeezed upwards increasing in height
Stage Four: Tsunami heads inland, destroying all in its path
Least common trigger of tsunamis
volcanic
Natural function of tsunamis
Rejuvenate the vegetation cover, creating new habitats and possibly over time increasing biodiversity
Which ocean is most likely to experience a tsunami
85% of tsunamis occur in the Pacific ocean
What countries are most at risk of a tsunami?
Japan, Kamchatka, Hawaii, islands in the southern and west Pacific, Chile, Peru, Mexico, and the northeast Pacific coast from Alaska to northern California
Minimizing the tsunami hazard
Detection and warning, structural control (walls and dykes), construction of runup maps, land use, probability analysis, education, tsunami-ready status
Tsunami runup map
Shows the level to which the water travelled inland
Tsunami watch
Notification that an earthquake that can cause a tsunami has occured
Tsunami warning
Tsunami has been detected and is coming
Inundation maps
Predict and display the extent that waves will run up the shoreline and inundate the adjacent land.
3 recent canadian tsunamis
- Halifax, Nova Scotia (1917)
- Port Alberni, British Columbia (1964)
- Kitimat Inlet, British Columbia (1975)
5 basic types of landslides
- Falling: free fall of earth material
- Sliding: downslope movement of coherent block of earth along a plane
- Flow: downslope movement of unconsolidated material
- Slumping: sliding of rock or soil along a curved plane
- Creep: very slow flowage
Forces that impact landslides
Driving forces
Resisting forces
Calculating factor of Safety
resisting forces/driving forces
Variables that impact driving and resisting forces
Material type Slope and topography Climate Vegetation Water Time
Debris flow
Thick mixtures of mud, debris, and water; can move fast or slow, depending on conditions
Structural controls of landslides
- Slope drainage
- Slope reduction
- Engineering to resist mass movement
- Engineering to mitigate damage
Human processes in the initiation of landslides
Timer harvesting
Urbanization
Mining
Conditions to be considered in the prediction of landslides
- Slopes and seismic activity
- Geology and structure
- Surface water buildup
- Topographic and vegetation features
- Accelerated creep
Drainage basin
Region drained by a single stream or river
Discharge
Volume of water moving through a cross section of a river per unit of time
3 channel patterns of streams and rivers
- braided: large number of intersecting active channels
- anastomosing; 2+ channels and intervening stable islands or bars where sediment is temporarily stored
- meandering: single channel shaped like a snake
Flash flood
Associated with intense rainfall events such as during convective thunderstorms
E.g. Saguenay River in Quebec (1996)
Regional Floods
Cover large areas in extensive river valleys with flat topography
E.g. Red River in Manitoba
Impacts of floods
Primary Impacts:
- Loss of life, primarily from drowning
- Injury
- Damage to structures
- Soil and vegetation erosion and deposition
Secondary Impacts
- Pollution
- Hunger
- Disease
- Displacement of people
- Losses of services and income
Structural and non-structural adjustments for floods
Structural Adjustments
- Floodproofing
- Channelization
Non-Structural Adjustments
- Floodplain Regulation
- Relocation
- Channel Restoration
Hydrograph
Graph showing changes in stream discharge, water depth, or stage over time
Flood stage
When the elevation of the water surface has reached a level likely to cause damage to personal property
Recurrence interval of a flood
Average time between flood events that are of equal or greater magnitude
Downstream flood
Covers wide areas and are caused by regional storms or spring runoff
Natural service functions of floods
Fertile lands
Aquatic ecosystems
Sediment supply
Channelization
Straightening, deepening, widening existing stream channels
Watershed or catchment
An area that contributes surface water to a stream
Gradient
The average slope of a stream channel; that is, the ratio of the vertical drop of the stream over the horizontal distance of the drop
Headwaters
The tributaries of a stream or river near its source
Base level
The theoretical lowest elevation to which a river can erode at a particular time
Stream or total load
The sum of the dissolved, suspended, and bedload that a stream or river carries
Epicenter
- where earthquake starts
- place on the surface of Earth above where the ruptured rocks broke to produce the Earthquake
Focus or Hypocenter
- point of initial breaking
- directly below epicenter
Earthquake cycle
- long period of inactivity along a segment of a geologic fault.
- accumulated elastic strain produces small earthquakes. 3. consists of foreshocks, may occur only hours or days prior to the next large earthquake (stage may not occur)
- The mainshock, the major earthquake, and its aftershocks
Strain
deformation resulting from stress
elastic strain
deformation that isn’t permanent provided that stress is eventually released
elastic rebound
occurs after an earthquake