Advanced Hazards and Disasters Flashcards
define hazard
(cause) is a potential threat to humans and their welfare, an environmental hazard is all the potential threats facing human society by events that originate in and are transmitted through the environment. In order from decreasing severity: Hazards to people – death, injur, disease, mental stress. Hazards to goods – property damage, economic loss. Hazards to environment – loss of flora and fauna, pollution, loss of amenity. A naturally occurring or human-induced process, or event, with the potential to create loss, i.e. a general source of future danger. (Hazard is potential). Venn diagram, Hazard overlaps physical system and human system. Physical Exposure + Human Vulnerability
define risk
(effect or likely consequence) is the probability of an event causing a loss or of a hazard occurring and creating loss. (Probability is risk)
define disaster
(actual consequence) is a hazard that has been realized; the realization of hazard. Social phenomena that occur when a community suffers exceptional levels of disruption and loss due to natural processes or technological accidents
define vulnerability
is a possible future state that implies high risk combined with an inability to cope. Human vulnerability is a more comprehensive term - the degree of resistance offered by a social system to the impact of hazardous event.
define magnitude
size or intensity of hazardous processes. Hazard magnitude can be determined by the peak deviation beyond the threshold on the vertical scale. A number assigned to a quantity, such as weight, and used as a basis of comparison for the measurement of similar quantities
define duration
Hazard duration from the length of time the threshold is exceeded on the horizontal scale. The length of time something continues or exists.
define frequency
The number of times and event recurs during a set time period. The number of periods or regularly occurring events of any given kind in unit of time, usually in one second.
define recurrence intervals
or return period, is the time that ,on average, elapses between two events that equal, or exceed, a given magnitude. Is based on the probability that the given event will be equaled or exceeded in any given year. For example, assume there is a 1 in 50 chance that 6.60 inches of rain will fall in a certain area in a 24-hour period during any given year. Thus, a rainfall total of 6.60 inches in a consecutive 24-hour period is said to have a 50-year recurrence interval. Ten or more years of data are required to perform a frequency analysis for the determination of recurrence intervals
define tangible vs. intangible impacts
Tangible are those for which it is possible to assign monetary values (physical damage to property, loss of business or industrial production, donated aid, and reconstruction grants) while intangible, although real, cannot be properly assessed in monetary terms (Loss of national heritage (e.g. art treasures), stress, inconvenience, post-recovery illness, deposits of fertile ash/silt for agriculture, scenic building land (e.g. water frontage), and tourism potential (e.g. volcanic sites))
define direct vs. indirect impacts
Direct losses are the first order consequences that occur immediately after an event, such as deaths and economical loss, and are much easier to measure. Indirect impacts emerge later and may be more difficult to attribute to the event, such as mental illness following event, property value decrease, and relocating
define perception
How a person sees a risk and the level of threat they believe them to be
define psychometric paradigm
uses psychophysical scaling and multivariate analysis techniques to produce quantitative representations or “cognitive maps” of risk attitudes and perceptions. focus on the roles of affect, emotion, and stigma in influencing risk perception.
A cognitive road map based upon how an individual perceives the level of dread risk and unknown risk associated with a particular hazard. It is used to better understand how the “layperson” judges risk.
define na-tech disaster
also known as hybrid disasters , which occur when natural hazards, such as earthquakes or floods, result in dangerous spills of oil , chemic,lal or other dangerous materials . Common form of na-tech disaster is risk of death or injury to road vehicle occupants caused by local weather conditions, such as snow or tornadoes. Environmental hazards: Natural Processes (extreme geophysical events) and technological accidents (severe system failures)
Refers to a hybrid type disaster which is in part human caused and naturally occurring. This would include an earthquake which causes a chemical spill or a human induced natural hazard like desertification.
define fault or event tree
uses a process of inductive logic that can be applied whenever a known chain of events must take place before a disaster can occur.
A systematic method used to investigate the cause of an accident. These trees are used to evaluate the pathways leading to a failure in a system.
Give an example of how risk and hazard are related.
Example of Hazard and Risk: The difference between hazard and risk can be illustrated through two people crossing an ocean, one in a large ship and the other in a rowing boat. The hazard (deep water and large waves) is the same in both cases but the risk (probability of capsize and drowning is very much greater for the person in the rowing boat.
Where are earthquakes most common and why do they occur there?
EQ are predominantly at tectonic plate boundaries
- 80 % circum-Pacific belt
- 15% Mediterranean-Asiatic
- 5% interiors of plates and MORs
They occur there due to the presence of plate tectonic boundaries:
Transform: dominant stress is shear
Divergent: dominant stress is tension
Convergent: dominant stress is compression
What causes earthquakes?
Cause of LARGE Earthquakes: magma migration and volcanic eruption, Sudden movements along a fault Fault=fracture or crack along which movement (displacement) occurs. Faults develop when regional forces create a large enough STRESS differential to cause movement.
Cause of MOST earthquakes. Sudden movements along a fault, Fault=fracture or crack along which movement (displacement) occurs. Faults develop when regional forces create a large enough STRESS differential to cause movement.
An earthquake is what happens when two blocks of the earth suddenly slip past one another and release stored stress. The blocks experience movement and become displaced. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter (focus), and the location directly above it on the surface of the earth is called the epicenter.
What hazards are associated with earthquakes (including secondary hazards)? (Hint 6)
- Liquefaction of ground—unconsolidated materials saturated with water behaves as a fluid
- Fire
- Landslides
- ground failure
- Tsunami
- Ground shaking–Majority of damage and toll on human life caused by structural collapse
List how earthquakes are measured (Hint 3 ways)?
By size on Richter (1935), Moment Magnitude, Mercalli (qualitative)
Where are volcanos most common and why do they occur there?
90% at plate boundaries
-10% at hot spots
Nearly 80% of magma reaching the surface occurs along the spreading centers
-rift valleys and Oceanic ridges
What causes volcanos?
Spreading plate margins
Where plates move away from each other at spreading or divergent plate margins, volcanic eruptions are gentle extrusions of basaltic lava. Most of these occur underwater where magma rises from great depth below to fill the space created by seafloor spreading which occurs at a rate of about 10 centimetres a year.
Subducting plate margins
At subducting plate margins, one plate is pushed under a neighbouring plate as they squeeze together. In addition to the old, weathered plate being forced down and melted, wet sediment and seawater is forced down creating andesitic lava and more violent eruptions containing ash. These volcanoes form classic cone shapes.
Some volcanoes are found at great distances from plate boundaries and are referred to as intraplate, within plate or hot spot volcanoes. These form above hot mantle upwellings or plumes which rise from great depths. As the plate overlying the plume moves away from the hot spot and a new volcano is formed, the previous one cools to become dormant and eventually extinct. This sequence forms a volcanic chain such as that currently found in the Hawaiian Islands. Hotspot volcanism forms very large, low gradient shield volcanoes and are similar in composition and eruption style to those found at divergent plate boundaries.
What hazards are associated with volcanos (including secondary hazards)? (Hint 9)
Volcanic Earthquakes Directed Blast Tephra - rock fragments released during an eruption. Volcanic Gases Lava Flows Landslides Tsunamis Pyroclastic Surge Pyroclastic Flows Lahars - mudflow
*Other secondary effects could be things like climate change (cooling) due to the release of material and gasses into the upper atmosphere.
How are volcanos measured?
Volcanic eruptions are measured using the VEI (Volcanic Explosivity Index). It is based on the volume of ejecta, Height of the eruptive column, Qualitative descriptions (“gentle”, “effusive”, “explosive”, “cataclysmic”, etc.), Style of past activity, and height of spreading of the eruptive plume head (in troposphere or stratosphere). The scale goes from 0 to 8 with 0 corresponding to “nonexplosive” and 8 corresponding to “megacolossal.”
