Natural Hazards Exam 1

Define hazards

Something that may cause the loss of human life, property damage, social and economic disruption, or environmental damage (threat to humans).

Define disaster

An event that causes huge disruption to human communities and compromises their ability to recover and recovery resources.

Define risk

The probability of the occurrence of a hazardous event that causes negative impacts

High physical exposure + high vulnerability = high risk
If either is low, risk drops.

Threats of natural hazards/disasters:

1. To people’s health
   (death, injury, disease, mental stress)

2. To goods
   (property damage, economic loss)

3. To the environment
   (loss of biodiversity, pollution, loss of ecosystem services, loss of amenities)

Scales of natural hazards:

• Local

• Regional

• National

• Global

What are natural hazards?

Hazards that originate in nature and impact humans

What are technological hazards?

Hazards caused predominately by humans / human inventions

What are socionatural hazards?

Natural hazards that are made worse by human activity
(quasi - almost natural or socionatural hazards)

What are Na-tech (Natural-Technological) socionatural hazards?

Technological hazards that are triggered by natural hazards

Examples of natural hazards:

1. Volcanic

2. Seismic (Earthquakes)

3. Tornadoes

4. Wildfires

5. Flooding

6. Hurricanes

7. Drought

8. Heavy rain / snow
   
   

(Many natural hazards can be considered socionatural hazards)

Examples of socionatural hazards:

1. Landslides

2. Flooding

3. Droughts

4. Wildfires

5. Diseases

Examples of technological hazards:

1. Air pollution

2. Oil spills

3. Human-caused wildfires

4. Water pollution

5. Powerplant failures

6. Dam Failures

Examples of Na-tech socionatural hazards:

1. Powerplant failures after or during extreme weather

2. Dam failures after or during hurricanes

3. Water pollution after rain

4. Bridge failure because of earthquake / soil liquefaction

Define physical exposure:

The degree to which people or property are located in a hazard-prone zone

Example: A house next to a river has a high physical exposure to flooding, which a house on a hill nearby does not.

Define human vulnerability:

How well a person can handle, survive, or recover from a hazard. Depends on things like income, health, and support systems.

Physical exposure Vs human vulnerability

Physical exposure: Whether people or property are located in a hazard prone area

Human vulnerability: A person / community’s ability to recover from a hazard’s impacts

Define paradigms:

Paradigms are models and frameworks used to guide on how to do research or create policies to manage problems

(Paradigms change and evolve as limits as understood or realized)

Engineering paradigm:

The idea that hazards can be controlled and contained through technology, engineering, and military operations, like dams and flood walls.

Behavior paradigm:

The idea that land-use planning is key, and that government, insurance companies, and real-estate markets should guide society on where to live safely

Development paradigm:

The idea that vulnerability to hazards is caused by economic development, where lower income communities aren’t able to prepare for or recover from disasters

Complexity paradigm:

Combines social and natural sciences evenly to understand the different ways people experience hazards, shaped by ideas about sustainability

ideas about sustainability: Using just the right resources without creating problems for the future or other communities

Hurricanes in Central Marica: Mitch (1998)

• Category 5 hurricane

• Hit Central America, mainly Honduras

• Caused Mudslides and flash floods

• 11,000 people killed

• $5 billion in damages

Hurricanes in Central America: Felix (2007)

• Category 5 hurricane

• Hit Nicaragua and Honduras

• Moved faster than Mitch, so less rainfall but very strong winds

• 133 people killed

Complexity perspective: Mitch vs Felix

Mitch moved slowly, dropping massive rainfall that caused deadly mudslides and floods.

Felix moved fast, so less rain, but its strong winds destroyed homes

Bam Earthquake (Iran 2003)

• Magnitude 6.6 earthquake in Southern Iran

• Population of 128,000

• Around 26,000 - 43,000 killed

• 70% of buildings collapsed

Bam earthquake: Physical reasons for severity

• Rupture happened on a lesser known fault

• Shaking lasted 15 seconds

• Shallow hypocenter sent seismic energy directly into the city

Bam earthquake: Social reasons for severity (buildings)

• Old buildings made of adobe (clay and straw) which collapses easily

• Newer buildings didn’t meet seismic codes (too much sand in cement, untreated termite damage on buildings)

• Likely under-enforced because Bam had no recent history of earthquakes, despite being in an earthquake prone area

Bam earthquake: Social reasons for severity (emergency response)

• Most emergency facilities were destroyed, half of emergency personnel killed

• Trapped survivors died of hypothermia overnight

• Conflicts between Iranian agencies and no clear protocol for international aid delayed help

Swiss cheese model

Disasters happen when weaknesses (holes) in different layers of protection line up.

Each layer = a safeguard (building codes, emergency responses, etc.)

In Bam: weak buildings + poor emergency responses = more severe disaster

Main hazard impacts:

• Deaths

• Economic loss

• damage to property and crops

Reporting disaster: Reinsurance companies and their biases

• Purpose: Insurance and catastrophe risk assessment

• Tracks events relevant to insurance losses, including many smaller events

• Use detailed loss modeling, insurance claims, industry estimates

• Insurance losses are their major focus and are well recorded

• Uninsured losses often estimated using models, less reliable

Reporting disaster: CRED / ED-DAT

• EM-DAT = Emergency Events Database, maintained by CRED

• Purpose: humanitarian / disaster risk monitoring (not insurance focused)

• Preferred database of UN agencies

• Covers natural and technological disasters

• Counts as “significant disaster” if: 10+ deaths, 100+ people affected, state of emergency declared, OR international aid requested

Reporting disaster: The media and their biases

• Tends to focus on dramatic, high death toll, or visually striking disasters

• Can underreport smaller or “quieter” disasters (slow-onset, less visual)

• Coverage often shaped by proximity to wealthy western counties

• Can skew public perception of which hazards are most frequent or dangerous

Issues with databases: Inconsistencies in standards and purpose of organization/company

• No standardized methodology across organizations for counting deaths / damages

• Each organization’s purpose shapes what it counts (humanitarian Vs insurance Vs media attention)

• Disagreement on what counts as a “disaster” or where it starts/ends

• Secondary hazards (landslides after earthquakes) may or may not be counted as part of the same event

Results: same disasters can have different reported numbers depending on the source

Time trends: Number of disasters 📈

• Overall number of recorded disasters (natural + technological) has increased over time (due to climate change)

• Technology has also improved, which has inflated the number due to reporting being more accurate

• Technological events are included in the overall disaster count, not tracked separately

Time trends: Total deaths

• Total death trends contradicts the idea that fewer people are dying from disasters

• Global pattern of declining deaths (excluding COVID) is inconsistent in more recent data

• Likely due to new challenges in hazard risk management

Time trends: Death rate (deaths / number of disasters)

• Death rate = death / number of disasters

• Dearth rate is lower in 2000 - 2009 compared to 1980-1999

• Deaths per events are likely going down globally, while disasters are happening more frequently due to climate change

Spatial patterns: HDI (Human Development Index) and Disaster Risk Management

• HDI: scale 0-1, measures health, education, and standard of living

• Disaster Risk Index: scale 0-8, measures risk of disaster related death

Spatial patterns: Risk Vs Development

• Low/Medium Human Developed countries (LHD/MHD): higher deaths from disasters

• Medium Human Developed countries (MHD): higher disaster affected people

• Medium/High Human Developed countries (MHD/HHD): higher economic loss

Vulnerability: Indicators

• Income, access to food, age, gender

• Race/ethnicity, health, sexual orientation

• Occupation, religion, education, political system

• homelessness, disability

Vulnerability: Gender

• More men die from occupational hazards (construction accidents, mining collapses, black lung disease)

• More women may die during heatwaves as they tend to live longer, with elderly isolated women being more vulnerable

Vulnerability: Burundi’s (food crisis example)

• Floods, landslides, and droughts destroyed farmland, causing a food crisis that affected 1.2 million people

• Refugees from DR Congo increased demand for aid

• 2024 funding cuts let to reduced food rations (aid only reached 50% of recommended daily calories)

Vulnerability: Cuba (car example)

• Us embargo/sanctions make it hard to import new cars or parts

• Older cars stay in use with missing/replacement parts, making them more hazardous

Define resilience

The ability of a system, community, or society to resist, absorb, accommodate, and recover from a hazard’s effects in a timely way, including restoring basic structures and functions

Resilience: Colorado example

The City of Boulder Colorado restricts new development or repairs in flash flood areas

Resilience: North Caroline example

• Statewide law restricts development on mountain ridges at 3,000+ feet

• Redevelopment focus:
  - public education on landslide risks
  - managing vegetation
  - drainage / slope grading

Define earthquakes

Caused by sudden rock movement along a fault (a zone of weakness in rock)

(When slow building stress exceeds the strength of the rock along the fault, the rock breaks creating fractures. The original subsurface area of rupture is called the hypocenter or focus. Depth: 0.700 km)

Earthquake: Hypocenter / Focus

The original underground area where the rupture starts

Earthquake: Epicenter

The point on the surface directly above the hypocenter

Earthquakes: factors linked to impact / shaking

• Depth of hypocenter: shallower = stronger shaking

• Distance from epicenter: closer = stronger shaking

• Direction of rapture: can make shaking stronger in some directions

• Rock / soil conditions: soft soil and loose rock fragments amplify shaking

• Building type: older + poorly built = more damage

Earthquakes: foreshocks and aftershocks

• Foreshocks: a quake that happens before the main shock

• Aftershock: A quake that happens after the main shock

Earthquakes: Intensity

Describes how strong the shaking feels as a specific location. One earthquake has many different intensity values depending on where you are

Earthquakes: Magnitude (moment scale)

Moment magnitude (MW) is today’s standard, replacing Richter’s local scale.

Based on:

• Area of the fault that broke

• Displacement

• Average rigidity of rock

One rock has only one magnitude value

Earthquakes: Intensity vs Magnitude

• Magnitude: one single value per earthquake, measures total energy released

• Intensity: many values per earthquake, measures shaking/effects at different locations

Earthquake waves: P waves

• Also called primary / pressure waves

• Body waves (travels first, fastest)

• Compression motion: travels through solids AND liquids/gases

• Speed: 8 km

• Shakes houses mostly vertical, sometimes not felt

Earthquake waves: S waves

• Also called secondary / shear waves

• Body wave ( second to arrive, 60% slower than P waves)

• Shear motion: only travels through solids

• Speed: 4-5 km

• Shakes house complex, mostly horizontal

• Causes more damage than P waves

Earthquake waves: Love waves

• Surface wave

• Moves side to side (like shaking a rug horizontally)

• Forms when body waves reach the surface

Earthquake waves: Rayleigh waves

• Surface waves

• Moves up and down like water waves

• Complex motion: Both vertical and horizontal

Earthquake waves: Body waves

• Travels through the inside of the earth

• Arrives first (P waves, then S waves)

• Faster than surface waves

Earthquake waves: Surface waves

• Travels along the Earth’s surface only

• Arrives later than body waves

• Slower but lasts longer and cause more damage

• Can shake an area for 30+ seconds

Earthquake waves: Early warning systems

Sensors detect the fast P-wave first, giving seconds to minutes of warning before the more damaging S-wave hits. Used to shut off gas lines, stop elevators, and trigger alarms

Earthquake waves: foundation anchorage

Steel anchor bolts and mental framing ties lock the house to its foundation so S-waves dont slide it off it’s base

Earthquake waves: Shear walls

Plywood or diagonal bracing panels absorb the sideways twisting force caused by S-waves

Earthquake waves: Flexible material

Wood and steel framing bend under stress instead of cracking, unlike brick or concrete

Earthquake waves: internal strapping

Heavy furniture and appliances are bolted to wall studs so they dont tip over during shaking

Resilience: Financial capital

access to money and insurance

Resilience: Natural capital

• Access to useful natural resources: Land, water, minerals, forests

• Wetlands, biodiversity, stable soils

Resilience: Social capital

• Family, friends, neighbors, trust, mutual help

• Community centers, and similar

Resilience: Human capital

Education, skills, good health

Resilience: Physical capital

Infrastructure, roads, shelter, transportation, sanitation

Define Lithosphere

The rigid outer layer of the Earth, broken into plates that move on top of the asthenosphere

Convergent boundaries

Often cause earthquakes because plates collide and become locked, building stress. Subduction zones can produce very large earthquakes

Transform boundaries

Commonly cause earthquakes as plates slide past each other and friction causes them to stick and then slip. May not be as strong as quakes linked to convergent boundaries

Divergent boundaries

Can cause earthquakes as plates pull apart and magma rises, but these earthquakes are smaller

Define fault

A fracture in the Earth’s crust where blocks of rock have moved past each other

Define fault plane

The underground surface along which the fault’s movement happens

Define fault line

Where the fault plane meets the Earth’s surface

Normal fault

Vertical / oblique movement: the footwall stays down while the hanging wall moves up

Reverse fault

Vertical oblique movement: the footwall stays down while the hanging wall moves up

Thrust fault

Oblique movement, similar to a reverse fault but with stronger horizontal displacement

Strike-slip fault

Horizontal movement: the two blocks of rocks slide sideways past each other