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Volcanoes are convergent boundaries so it is often that
earthquakes occur near them- sometimes in isolation in the ocean
Earthquakes are caused due to the
friction caused during subduction
A landslide can cause
large floods and tsunamis when they hit rivers or other large water bodies
Adaptations are ways in which human activities are
altered to take into account the increasing risk of hazards
Disasters are
major hazard events that impact a drastic amount of persons, creating many casualties (BIG HAZARD)
Hazard events are
occurrences of hazards that change demographic, economic and/or environmental conditions
Risk is the probability of a hazard event causing
harmful consequences, deaths, injuries, property damage economy and environment
Hazard perception is the degree to which
a hazard is considered to be. threat by different people
Resilience is the ability to protect
lives, livelihoods, and infrastructure from destruction, and to the ability to recover after a hazard
Risk of disaster [R] is measured by
(Severity of hazards [H] x People vulnerability [V])/ Capacity to cope [C]
Plate margins are
zones at which the most magma is produced
Ground technology is used to measure
gas emissions, grounds of formation, and resulting earthquake activity
Technology, monitoring, and evidence from past eruptions are used to model and create
eruption scenarios, hazard maps, and eruption timelines
As scientists can’t always get their predictions right, governments often
refuse to listen, as preparations and monitoring require large funds
The pressure release model measures risk by considering
the progression of vulnerability (root causes, dynamic pressures, unsafe conditions) and natural hazards
Root causes include
limited access to power, structures, resources, and political and economic ideologies
Dynamic pressures include
a lack of training, local investment, press freedom, with rapid population change, rapid urbanization, and deforestation
Unsafe conditions include
physical environmental, local economy, social relations and public action pressures.
Natural hazards include
earthquakes, flooding, landslides, volcanic eruptions, droughts, virus and pests, and wind storms
Earthquakes occur along plate boundaries, especially
convergent ones forming from subduction.
Friction is created through the opposing
forces in the two plates during subduction
Friction created through boundaries sends
seismic shock waves and vibrations that make up an earthquake
The stronger and shallower the earthquake is
the more violent its destruction
Earthquakes under oceans create
big, destructive waves called tsunamis
Around 100 out of 500,000 earthquakes per year
cause damage
The Moment magnitude scale is preferred to the Richter scale due to its
lack of upper limit
Both the moment magnitude scale and the richter scale
increase in magnitude 10x for every whole number increase in value
Using historical earthquake data, governments and scientists are trying to
predict when and where the next earthquakes will occur
Engineers are investing in building infrastructure with
lighter roofs, flexible structures and stronger foundations to deal with earthquakes
Countries with good earthquake-proof infrastructure include
Taiwan and Japan
The valdivia earthquake in Chile was
the largest earthquake ever recorded with a magnitude of 9.5, lasting 10 minutes.
The valdivia earthquake in Chile created
a tsunami which reached as far as Japan, affecting the globe
Risk that comes with an earthquake include
building codes not being up to date and poor governance and city planning restricting access to essential aid
Hospitals and services built on the edges of towns are examples
of essential services being build quickly on the cheapest land and being inaccessible in times of disaster
Roads collapsing
obstructs people’s access to essential resources + facilities
It’s not earthquakes that cause casualties,
it’s poor buildings
Stress
force per unit area acting on a plane within a body
Tensional stress
Builds in faults on divergent plant boundaries
Compressional stress
Builds up in faults on convergent plate boundaries
Sheer stress
Builds up in faults on plate boundaries moving side by side
Seismic waves
transfer energy in all directions
P-waves are the
deepest in the ground and produce the smallest waves in a seismograph
S-waves are the
precursor waves we feel, a little larger than P-waves on seismographs
Surface waves are
the largest waves seismographs and are the waves creating the impactful waves
Surface waves include
Love and Raleigh waves
Releigh waves move
in circular motions (like jump ropes)
Love waves move
in sideways motions (like s-waves on their sides)
S-waves move
in wave motions
P-waves move in
compressional motions
Earthquakes root from a focus which is
a point along the fault line where pressure builds and releases
The point directly above the focus, on the surface is the
epicenter, where energy on the surface will be the greatest (as the point of origin)
Wave fronts in the crust become
seismic waves on the surface
The fault line is
the line along which two plates slide against each other violently in opposing directions
Liquefaction is
a primary hazard of earthquakes where the ground turns to liquid
Shaking, cracking and opening of the ground are
primary hazards of earthquake events
Small, triggered fires and landslides are
secondary hazards of earthquake events
Mercalli scale is
based on observable earthquake damages and the effects at a given location on a scale of 1 to 12 (equal to 1 to 8 on Richter)
Richer scale is
calculated from the earthquake’s largest seismic wave amplitude and considered movement on a scale of 1 to 10 (each 10 times more intense than the last)
Mercalli scale’s benefits include
Intensity being directly linked to the physical effects felt making it more tangible and accessible for more people
Richter’s scale’s benefits include
Quantifiable, scientific and hence, accurate measures of earthquake strengths that allow for standardized comparisons of earthquakes
Mercalli scale’s limitations include
it is subjective and harder to compare and can use descriptions not everyone has experience with based on their environments.
Richter scale’s limitations include
it doesn’t reflect vertical movement and is valid for certain frequencies and distances only. It is also every inaccessible to people without prior knowledge
The moment magnitude scale
considers distortion and displacement of the ground along with the amplitude measurements of the Richter scale to create a more accurate measurement
The moment magnitude scale increase
32 times in energy released with every additional magnitude
Creeping zones
earthquake zones where slow and steady movements occur allowing for energy released slowly
Slip zone
earthquake zones where there is build up of stress and it is released violently
Understanding the frequency of earthquake occurances
can help model future fault slips and inform governments of time frames within which an earthquake is expected so they can plan around and mitigate its effects
Information needed for earthquake risk management include
Population density, access and roads to health services, urban landscapes and construction
As magnitudes of earthquakes increase
the frequency of their occurrences decrease
In general, earthquakes occur
more frequently than volcanos as there are more fault lines than hot spots
Technological advancements can play a huge role in increasing reported earthquakes as
more small earthquakes are being recorded, giving the media the illusion of their increased frequency
Why might people choose to live in areas affected by earthquakes?
Lacking socio-economic means, indigenous/emotional connections to land, low risk perception hence people live unaware of the hazard or able to mitigate it or because of present earthquake proofed infastructure
How can planning reduce the effects of an earthquake?
People could be evacuated, buildings could be proofed and checked for stability, land use could be further developed to reduce urban risk, education to respond to earthquakes could prevent increase casualties as well as readily available health services being prepared
Earthquake predictions are based on
Date and time, location and magnitude
Suggested precursors to earthquakes include
radon in local water, unusual behavior in animals, increasing magnitudes of events to suggest foreshock
A real earthquake prediction is
made on scientific basis in probabilistic terms
Economic reasons to live near earthquake zones
An Earthquake pushes the land further up, thus helping vegetation flourish as it allows nutrients and minerals to be deposited evenly, creating a very fertile soil. There are many minerals in tectonically active zones
Cultural reasons to live near earthquake zones
Ancestral lands or inherited ways of living, interpretation of earthquakes as mother nature’s response
Social reasons to live near earthquake zones
People may not be as well educated hence they might be unaware of the risks, it can be close to family, or just a simple way of living
DROP, COVER, HOLD is a
public earthquake response strategy aimed to protect people and their vital organs from overhead debris
DROP, COVER, HOLD advantages
Catchy and easy to remember even with language barriers, applicable despite income or social class, inexpensive strategy
DROP, COVER, HOLD disadvantages
Needs sturdy structure to hide under for debris inflection- might not be so available in lower income areas and they don’t mitigating risk for disabled persons as still exposed to debris
DROP, COVER, HOLD is used in
USA for the Great ShakeOut and globally as a first, applicable measure across all levels of development
The US Great Shake-out is
an earthquake preparedness drill that occurs across the entire country and has around millions of participates
The US Great Shake-out advantages include
all societal units (businesses, families, etc.) to practice together for greater cohesion in real scenario, reaches a wide range of people and educates them, people are incentivized to plan for it and practice it, and people can properly check up on emergency supplies, etc.
The US Great Shake-out disadvantages include
disrupting daily lives the more it is practiced nationwide, requires great organization and cohesion throughout the country and its timezones
Earthquake preparedness infrastructure includes
structural mitigation measures, non-structural mitigation measures, contents mitigation, and design modifications
Structural mitigation measures are
the strengthening of building elements (foundations, columns, load-bearing walls, floor/roof diaphragms) to resist seismic and lateral forces.
Non-structural mitigation measures are
the improvements of seismic resistance of components like parapets, chimneys, HVAC systems, and windows through bracing or anchoring.
Contents mitigation is
Securing heavy items (bookcases, file cabinets, electronics) to prevent injuries if they fall during hazards (e.g., tsunamis, floods, major hazmat sites).
Design medications are
the encouragement for appropriate building designs in vulnerable areas; discourage high-rise structures and large industrial facilities in these regions.
Earthquake ready kits are
bags of emergency foods, water, flashlights, protective pieces and first aid kits in the case of earthquakes with limited support
Earthquake ready kits
help mitigate earthquake hazards as people are prepared to access basic needs for long periods of time
Earthquake ready kit disadvantages are
incur personal costs- not available to all- Materials can expire before they are used
Earthquake ready kits are used in
Japan to deal with their frequent earthquakes
Liquefaction is the increased pore water pressure in soil causing water gaps between soil pores to increase in size which
liquefies the ground and decreases its load bearing capacity as friction in the top soil is overcome and soil forms heavy clumps and sinks to the bottom and water lifts up
What causes Liquefaction?
Heavy construction activities, earthquakes or volcanoes that cause intense shaking
Liquefaction ground deformation types include
Lateral spreading, ground oscillations, and settlement
Lateral spreading is
the horizontal displacement of ground after liquefaction as liquid soil flows towards divots in the land
Ground oscillations are
a back and forth movement of liquid soil that is triggered by further shaking, increasing the destabilization of infrastructure
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