Tectonic Hazards

Plate Boundaries and Their Characteristics

Divergent Margins

• Divergent margins, also known as constructive margins, are primarily found at ocean ridges where tectonic plates move apart.

• Characterized by numerous shallow-focus earthquakes, typically of low magnitude, most of which occur underwater.

• The process of sea-floor spreading occurs here, contributing to the formation of new oceanic crust.

• Example: The Mid-Atlantic Ridge, where the Eurasian and North American plates are diverging, leading to volcanic activity and the creation of new ocean floor.

• The geological activity at these margins is driven by mantle convection, which causes the plates to separate.

Convergent Margins

• Convergent margins involve the collision of tectonic plates, leading to significant geological activity including earthquakes and volcanic eruptions.

• The process of subduction occurs, where one plate sinks beneath another, often resulting in deep-focus earthquakes along the Benioff Zone.

• Example: The subduction of the Nazca Plate beneath the South American Plate creates the Andes mountain range and is responsible for frequent earthquakes and volcanic activity.

• The melting of the subducted plate generates magma that can lead to explosive volcanic eruptions due to high gas content.

• Collision zones, where two continental plates converge, can create large mountain ranges and are associated with shallow, high-magnitude earthquakes.

Conservative Margins

• Conservative margins, also known as transform or strike-slip boundaries, occur where plates slide past one another horizontally.

• These boundaries do not create or destroy lithosphere, resulting in no volcanic activity but are sites of significant earthquake activity.

• Earthquakes here can be of high magnitude due to the stress accumulation along faults, such as the San Andreas Fault in California.

• The movement can be classified as sinistral (left-lateral) or dextral (right-lateral), affecting the landscape and geological features.

• Example: The 1906 San Francisco earthquake, a result of movement along the San Andreas Fault, caused extensive damage due to its shallow focus.

Intra-Plate Earthquakes and Hotspot Volcanoes

Intra-Plate Earthquakes

• Intra-plate earthquakes occur away from tectonic plate boundaries, often reactivating ancient fault lines due to tectonic stresses.

• Example: The New Madrid Seismic Zone in the central United States, which has produced significant earthquakes despite being far from any plate boundary.

• These earthquakes can reach magnitudes of up to 7.5, demonstrating that tectonic activity is not limited to plate boundaries.

• The study of these earthquakes helps understand the distribution of seismic hazards in stable continental regions.

• Factors contributing to intra-plate earthquakes include the reactivation of old faults and the buildup of stress in the lithosphere.

Hotspot Volcanoes

• Hotspot volcanoes are formed by mantle plumes, which are columns of hot material rising from deep within the Earth.

• Unlike volcanic activity at plate boundaries, hotspots can occur in the middle of tectonic plates, such as the Hawaiian Islands and the Galapagos Islands.

• As the tectonic plate moves over a stationary mantle plume, a chain of volcanic islands is formed, with the oldest islands being the furthest from the plume.

• The eruptions at hotspots are typically basaltic and can be continuous due to the consistent supply of magma from the mantle.

• Example: The Hawaiian hotspot has created a series of islands, with the Big Island being the youngest and most volcanically active.

The Theory of Plate Tectonics

Key Discoveries and Concepts

• The theory of plate tectonics explains the movement of the Earth's lithosphere, which is divided into several large and small plates.

• Alfred Wegener proposed the Continental Drift hypothesis in 1912, suggesting that continents were once joined and have since drifted apart.

• Arthur Holmes introduced the concept of mantle convection in the 1930s, proposing that heat from the Earth's interior drives plate movements.

• The discovery of the asthenosphere in the 1960s provided evidence for the dynamic nature of the Earth's interior, allowing for plate movement.

• Palaeomagnetism studies revealed magnetic striping on the ocean floor, supporting the theory of sea-floor spreading at constructive margins.

Mechanisms of Plate Movement

• Mantle convection is driven by heat generated from radioactive decay in the Earth's core and mantle, creating convection currents that move tectonic plates.

• Slab pull occurs when a denser oceanic plate subducts beneath a less dense continental plate, pulling the plate into the mantle.

• Gravitational sliding at constructive margins allows oceanic plates to slide down slopes created by rising magma, facilitating sea-floor spreading.

• The interaction of these processes at plate boundaries leads to various geological phenomena, including earthquakes and volcanic eruptions.

• Understanding these mechanisms is crucial for predicting tectonic activity and assessing geological hazards.

Earthquake Dynamics and Effects

Earthquake Characteristics

• Earthquakes are caused by the sudden release of energy in the Earth's crust, resulting in seismic waves that radiate outward from the focus.

• The epicenter is the point on the Earth's surface directly above the focus, where the effects of the earthquake are most strongly felt.

• Earthquake waves include P-waves (primary), S-waves (secondary), and surface waves, each with different properties and effects on the ground.

• The magnitude of an earthquake is measured on the Richter scale or moment magnitude scale, with significant implications for potential damage.

• Secondary hazards from earthquakes include liquefaction, landslides, and tsunamis, which can exacerbate the impact of the initial seismic event.

Impact of Earthquakes

• The impact of earthquakes varies based on depth, magnitude, and distance from populated areas, influencing the level of destruction.

• Shallow-focus earthquakes (less than 60 km deep) tend to cause more damage than deeper ones due to their proximity to the surface.

• Historical examples include the 2010 Haiti earthquake, which had devastating effects due to its shallow depth and proximity to urban areas.

• Preparedness and response strategies are essential for mitigating the effects of earthquakes, including building codes and emergency response plans.

• Understanding the geological context of an area can help predict potential earthquake risks and inform land-use planning.

Seismic Waves Generated by Earthquakes

Types of Seismic Waves

• P-Waves (Primary Waves): The fastest seismic waves, traveling at approximately 8 km/sec. They are compressional waves that cause minimal damage compared to other wave types.

• S-Waves (Secondary Waves): Arriving next at about 4 km/sec, these waves shake the ground violently, leading to significant destruction.

• L-Waves (Love Waves): The slowest waves, traveling along the surface. They have a large amplitude and can cause severe damage, including ground fracturing.

Characteristics of Seismic Waves

• P-Waves cause vibrations through compression, similar to a shunt in a line of connected train carriages, resulting in less destructive force.

• S-Waves, being shear waves, create a side-to-side motion that can lead to extensive structural damage during an earthquake.

• L-Waves, with their horizontal vibrations, are responsible for the most severe surface damage, including fracturing and displacement of the ground.

Crustal Fracturing and Earthquake Impact

• Earthquakes can cause crustal fracturing deep within the Earth and also lead to surface buckling and fracturing.

• Major earthquakes, like the 2004 Indian Ocean tsunami, can rupture fault lines over extensive distances (up to 1000 km), generating significant energy pulses.

• Ground shaking from large earthquakes can last several minutes, often followed by numerous aftershocks, compounding the damage.

Secondary Hazards Associated with Earthquakes

Landslides and Liquefaction

• Landslides are common secondary hazards, particularly in geologically young mountain regions, contributing to high mortality rates in earthquakes (e.g., 30% of deaths in the 2008 Sichuan earthquake).

• Liquefaction occurs in water-saturated, loose sediments, causing the ground to behave like a liquid under intense shaking, leading to structural failures.

Effects of Liquefaction

• Liquefaction can cause buildings to sink, tilt, or collapse, with recorded tilts of up to 60 degrees in some cases (e.g., Japan 2011).

• The phenomenon undermines foundations, resulting in extensive damage to infrastructure, including roads and bridges.

Volcanic Hazards

Primary Hazards from Volcanoes

• Lava Flows: Can travel several kilometers from vents at speeds up to 40 km/h, primarily from basaltic lava at subduction zones and hot-spot volcanoes.

• Pyroclastic Flows: Dense clouds of hot ash and gas that can devastate areas, occurring mainly at composite volcanoes.

• Ash Fall: Ash can blanket large areas, causing vegetation loss and structural damage, particularly from composite and cinder cone volcanoes.

Secondary Hazards from Volcanic Eruptions

• Lahars: Volcanic mudflows triggered by rainfall on volcanic ash, capable of causing significant destruction in river systems.

• Jökulhlaups: Floods resulting from volcanic eruptions beneath glaciers, common in Iceland, leading to rapid meltwater release.

Understanding Natural Hazards and Disasters

Definitions and Models

• A natural hazard is an event with the potential to harm people and property, while a disaster is the realization of that hazard, resulting in harm.

• The UN defines a disaster as a serious disruption of community functioning, leading to widespread losses that exceed local coping capacity.

• The Degg Model illustrates the intersection of hazards and vulnerable populations, leading to disasters.

Risk and Resilience

• The hazard risk equation: risk = (hazard x vulnerability) / capacity to cope, indicating that increased hazard magnitude or vulnerability raises disaster risk.

• Resilience refers to a community's ability to cope with hazards and recover post-disaster, influenced by preparedness and resource availability.

Age and Vulnerability

• Age affects resilience, with older populations being more vulnerable; 66% of those over 60 live in less-developed regions, projected to rise to 79% by 2050.

• The Disaster Risk and Age Index highlights the increasing risk faced by aging populations in hazardous environments.

Comparative Analysis: Japan vs. Myanmar

Hazard Exposure and Preparedness

• Japan has a significantly high natural hazard exposure due to its susceptibility to tsunamis, earthquakes, and other natural disasters.

• Myanmar also faces a range of natural hazards but has lower preparedness and resilience compared to Japan, leading to higher vulnerability.

Understanding Vulnerability and Coping Capacity

Age as a Factor in Vulnerability

• Age significantly influences the vulnerability and coping capacity of populations, particularly the elderly.

• Older generations often face unique challenges during disasters, including mobility issues and health concerns.

• In countries like Japan, the ageing population increases vulnerability despite high coping capacity due to education and resources.

• In contrast, Myanmar's elderly population faces greater risks due to lower coping capacities and limited access to technology.

Comparative Analysis: Japan vs. Myanmar

• Hazard and Exposure Scores: Japan has a high natural hazard score due to tsunamis and earthquakes, while Myanmar is highly exposed to a range of natural hazards.

• Vulnerability Levels: Myanmar ranks 7th in disaster risk for elderly citizens, indicating high vulnerability, whereas Japan ranks 133rd due to better coping mechanisms.

• Coping Capacity: Japan's elderly population is generally well-educated and connected, while Myanmar's elderly face challenges like low internet access and education.

The Pressure and Release Model (PAR)

Overview of the PAR Model

• The PAR model illustrates how socio-economic factors contribute to disaster risk.

• It identifies three key components: root causes, dynamic pressures, and unsafe conditions that lead to disasters.

• For example, in Haiti, low GDP and rapid population growth create unsafe conditions that exacerbate disaster impacts.

Case Study: Haiti Earthquake 2010

• The 2010 Port-au-Prince earthquake had a magnitude of 7.0 but resulted in approximately 160,000 deaths due to poor socio-economic conditions.

• Root causes included extreme poverty and lack of infrastructure, while dynamic pressures involved rapid urbanization and inadequate education.

• Unsafe conditions were characterized by informal housing and high population density, leading to catastrophic impacts.

Impacts of Tectonic Hazards

Types of Impacts

• Social Impacts: Include deaths, injuries, and psychological effects on affected populations.

• Economic Impacts: Encompass loss of property, businesses, and infrastructure, often leading to long-term economic challenges.

• Environmental Impacts: Involve damage to ecosystems and physical landscapes, affecting biodiversity and natural resources.

Comparative Analysis of Tectonic Events

• Volcanic Eruptions: Generally have smaller impacts compared to earthquakes and tsunamis, with notable exceptions like the 2010 Merapi eruption in Indonesia.

• Earthquakes: Can cause widespread destruction, as seen in the 2015 Gorkha earthquake in Nepal, which resulted in 9,000 deaths and $5 billion in losses.

• Tsunamis: Often lead to the most significant impacts, such as the 2004 Indian Ocean tsunami, which caused 230,000 deaths across multiple countries.

Measuring Tectonic Hazards

Scales for Measuring Magnitude and Intensity

• Moment Magnitude Scale (MMS): Measures the energy released during an earthquake, using a logarithmic scale to indicate ground shaking intensity.

• Mercalli Intensity Scale: Assesses the effects of an earthquake based on human perception and structural damage, ranging from I (not felt) to XII (total destruction).

• Volcanic Explosivity Index (VEI): Quantifies the explosiveness of volcanic eruptions, providing a scale from 0 (non-explosive) to 8 (mega-colossal).

Relationship Between Magnitude and Impact

• The relationship between earthquake magnitude and death toll is complex and influenced by factors such as urbanization and preparedness.

• Secondary impacts like landslides and tsunamis can exacerbate the effects of an earthquake, leading to higher casualties.

• Development levels and access to emergency services significantly affect the outcomes of tectonic hazards.

Understanding Earthquake Intensity and Impact

Earthquake Intensity Measurement

• The older scale measures the intensity of shaking effects during an earthquake, rather than the energy released.

• Intensity is subjective and varies based on factors such as building type, ground conditions, and local infrastructure.

• This scale is not suitable for comparing earthquakes across different regions due to these variances.

Factors Influencing Death Toll

• The relationship between earthquake magnitude and death toll is weak due to various secondary impacts like landslides and tsunamis.

• Urban earthquakes tend to have higher death tolls compared to rural ones due to population density and infrastructure.

• Development level and preparedness significantly affect the number of casualties during an earthquake.

• Isolated areas may experience higher death tolls due to delayed rescue and relief efforts.

• A high-magnitude earthquake in an unoccupied area may result in no fatalities.

Volcanic Explosivity Index (VEI)

Overview of VEI

• The Volcanic Explosivity Index (VEI) measures the magnitude of volcanic eruptions on a scale from 0 to 8.

• It combines eruption height, volume of erupted materials (ash, gas, tephra), and eruption duration into a composite index.

• VEI eruptions from 0-3 are typically associated with shield volcanoes, while 4-7 are linked to composite volcanoes.

VEI Scale Characteristics

Hazard Profiles of Tectonic Events

Comparing Tectonic Hazards

• Hazard profiles allow for a comparative analysis of different tectonic events based on characteristics like magnitude, speed of onset, and duration.

• This method provides a clearer understanding of risks associated with each hazard, rather than simple rankings.

Characteristics of High-Risk Hazards

• High magnitude, low frequency events are often unexpected and can have severe impacts.

• Rapid onset events with low spatial predictability pose significant risks as they can occur without warning.

• Regional areal extent hazards affect large populations across various locations, increasing potential casualties.

Case Studies and Impacts of Tectonic Hazards

The 2005 Kashmir Earthquake

• The Kashmir earthquake had a magnitude of 7.6 and a ground shaking intensity of V!! (severe).

• The event caused 87,000 deaths and displaced 2.8 million people, with significant destruction of infrastructure.

• Factors contributing to the high death toll included poverty, poor building construction, and the region's geological conditions.

Impact of Development Level on Earthquake Outcomes

• A comparison of recent earthquakes with a magnitude of 7.7 shows varying death tolls based on Human Development Index (HDI) scores.

• For instance, the 2015 Nepal earthquake resulted in 9,018 deaths in a region with an HDI of 0.55, highlighting the impact of development on vulnerability.

• Factors such as population density, secondary hazards, and emergency response capabilities also play crucial roles in determining outcomes.

Governance and Vulnerability to Tectonic Hazards

Role of Governance in Disaster Preparedness

• Effective governance is crucial for meeting basic needs and ensuring community resilience during disasters.

• Land-use planning can mitigate risks by preventing habitation in high-risk areas prone to earthquakes or volcanic eruptions.

• Environmental management practices can reduce the severity of secondary hazards like landslides.

Factors Influencing Vulnerability

• Vulnerability is heightened in areas with low human development, where basic needs are often unmet.

• Poor housing conditions, low education levels, and lack of access to healthcare contribute to increased risk during disasters.

• Governance quality directly affects a community's ability to prepare for and respond to natural hazards.

Governance and Its Impact on Disaster Resilience

Understanding Governance

• Governance refers to the effectiveness of national and local governments in managing resources and ensuring public safety, health, and education.

• Good governance is crucial for disaster resilience, as it directly influences a community's ability to cope with natural disasters.

• Effective governance includes transparency, accountability, and the absence of corruption, which are essential for disaster preparedness and response.

• Historical examples, such as the 1999 Izmit earthquake in Turkey, illustrate how poor governance can exacerbate disaster impacts, leading to high casualties and damage.

• National disaster management agencies, like FEMA in the USA, play a vital role in enhancing resilience through planning and resource allocation.

• In developing countries, agencies like PHIVOLCS in the Philippines often face challenges such as underfunding and corruption, impacting their effectiveness.

Key Factors Influencing Vulnerability

• Meeting basic needs, such as food, water, and health services, is essential for enhancing a population's coping capacity during disasters.

• Land-use planning can mitigate risks by preventing construction in high-risk areas, such as floodplains or earthquake-prone zones.

• Environmental management practices, including reforestation and monitoring, can reduce secondary hazards like landslides and lahars.

• Community preparedness programs educate citizens on disaster response, evacuation procedures, and risk awareness, significantly improving resilience.

• Corruption, such as bribery and misallocation of funds, can lead to unsafe building practices and increased vulnerability to disasters.

• Openness in governance, characterized by a free press and public accountability, fosters better disaster preparedness and planning.

Geographical Factors and Their Influence on Disaster Impact

Population Density and Urbanization

• High population density in urban areas complicates evacuation efforts during disasters, as seen in the vicinity of Mt. Vesuvius in Italy.

• Urbanization increases vulnerability, as major earthquakes in cities like Kobe (1995) and Haiti (2010) resulted in significant casualties due to concentrated populations.

• Rural areas may initially experience less impact from disasters, but isolation can hinder rescue and relief efforts, exemplified by the 2005 Kashmir earthquake.

• Urban areas typically have more resources, such as hospitals and emergency services, enhancing their resilience compared to rural regions.

• The trade-off between resource availability and population density highlights the complexity of disaster management in different contexts.

• Understanding these geographical factors is crucial for effective disaster risk reduction strategies.

Case Studies of Disaster Impact

• Haiti (2010): HDI 0.48, with 160,000 deaths and 1.5 million homeless due to corrupt governance and inadequate infrastructure.

• Sichuan, China (2008): HDI 0.73, resulting in 69,000 deaths and $140 billion in economic losses, showcasing rapid government response due to impending Olympic Games.

• Japan (2011): The Tohoku earthquake and tsunami, an exception in developed countries, highlighted the importance of advanced disaster preparedness and response systems.

• These case studies illustrate how governance, geographical factors, and socio-economic conditions interact to influence disaster outcomes.

• The contrasting impacts of disasters in developed, emerging, and developing countries underscore the significance of context in disaster management.

• Effective governance and preparedness can significantly reduce the human and economic toll of disasters.

Trends in Tectonic Hazards and Disasters

Historical Trends in Disasters

• The number of hydro-meteorological hazards has increased, potentially due to climate change and environmental mismanagement, while tectonic hazards remain stable over time.

• Despite a stable number of tectonic hazard events, the frequency of disasters has risen, indicating improved reporting and response capabilities.

• Deaths from disasters have decreased significantly since 2000, attributed to better management and communication technologies.

• The number of reported disasters has stabilized, reflecting improved data collection and accuracy, with fewer unreported events.

• The increasing number of people affected by disasters correlates with population growth and urbanization in high-risk areas.

• Understanding these trends is essential for developing effective disaster risk reduction strategies.

Economic Impacts of Tectonic Disasters

• Economic losses from tectonic disasters are on the rise, driven by increased affluence and property ownership in both developed and emerging countries.

• Megadisasters, defined as high-magnitude events affecting multiple countries, skew data on disaster impacts due to their significant human and economic toll.

• Volcanic disasters, while less frequent, can affect large populations through evacuations, as seen with Mt. Merapi in Indonesia (2010).

• The trend of rising economic losses highlights the need for robust disaster preparedness and risk management frameworks.

• Historical data shows that while earthquake deaths have decreased overall, the impact of single catastrophic events can still be devastating.

• Understanding the economic implications of disasters is crucial for policymakers and disaster management agencies.

Overview of Tectonic Mega-Disasters

Definition and Significance

• Tectonic mega-disasters are large-scale natural events, such as earthquakes and tsunamis, that have significant regional or global impacts.

• Examples include the 2004 Asian tsunami, the 2010 Eyjafjallajokull eruption, and the 2011 Japanese tsunami, each demonstrating the interconnectedness of global economies.

• These disasters can lead to extensive economic losses and human casualties, affecting multiple countries and regions.

Historical Context and Case Studies

• Between 2005 and 2015, approximately 270 deadly earthquakes resulted in 433,000 deaths, with five disasters accounting for 412,000 of these fatalities.

• The Kashmir earthquake (2005), Sichuan earthquake (2008), and Nepal earthquake (2015) occurred in the Himalaya collision zone, collectively causing 40% of earthquake-related deaths in this period.

• The 2010 Haiti earthquake is notable for its high death toll, accounting for another 50% of the total deaths from earthquakes during this timeframe.

Impacts of Major Disasters

Economic and Human Impacts

• The 2004 Asian tsunami affected 14 countries, with significant economic losses in Indonesia, Thailand, Sri Lanka, and Somalia, marking it as one of the largest disasters in terms of area affected.

• The 2011 Japanese tsunami disrupted global supply chains, particularly in the automotive and electronics industries, highlighting the vulnerability of interconnected economies.

• The Fukushima nuclear disaster led to a shift in energy policies, notably Germany's decision to abandon nuclear energy.

Multiple Hazard Zones

• Multiple hazard zones are regions prone to various natural hazards, such as earthquakes, volcanic eruptions, and hydrometeorological events.

• Examples include California, Indonesia, and Japan, which experience frequent tectonic activity and are also affected by storms and climate variations.

• The 1991 eruption of Mount Pinatubo in the Philippines exemplifies how hydrometeorological hazards can exacerbate tectonic disasters, as heavy rainfall caused destructive lahars.

Prediction and Forecasting of Natural Hazards

Prediction vs. Forecasting

• Prediction involves accurately determining when and where a natural hazard will occur, allowing for timely evacuation and preparation.

• Forecasting provides probabilistic assessments of hazard occurrences, such as a 25% chance of a significant earthquake in the next 20 years, but lacks precision.

Techniques for Prediction

• Earthquakes cannot be predicted, but risk forecasting identifies high-risk areas and potential ground shaking zones for land-use planning.

• Volcanic eruptions can be predicted using monitoring equipment that detects changes in magma movement, such as tiltmeters and gas spectrometers.

• Tsunami prediction relies on detecting seismic activity and monitoring ocean conditions, but effective warning systems must be in place to ensure timely evacuations.

Hazard Management Cycle

Stages of the Hazard Management Cycle

• The cycle includes response, recovery, mitigation, and preparedness, with each stage informing the next disaster management efforts.

• Response involves immediate rescue and aid to save lives, while recovery focuses on rebuilding infrastructure and rehabilitating affected individuals.

• Mitigation strategies aim to reduce the impact of future disasters through land-use planning and resilient construction practices.

Park's Model of Disaster Response

• Park's Model illustrates the disaster response curve, comparing the quality of life before and after disasters across different development levels.

• Curve A represents a minor disaster with quick recovery, while Curve C depicts a major disaster with prolonged impacts on quality of life, as seen in the 2010 Port-au-Prince earthquake.

• Developed countries typically align with profiles A or B, while developing countries often correspond to profile C, indicating longer recovery times.

Strategies for Modifying Vulnerability and Resilience

High-Tech Monitoring and Prediction

• Advanced monitoring technologies can predict volcanic eruptions, allowing for timely evacuations and saving lives.

• However, these systems are costly and may not be available in developing regions, leading to potential 'cry wolf syndrome' if predictions fail.

• While effective in saving lives, these technologies do not prevent property damage.

Community Preparedness and Education

• Community education initiatives, such as preparation days and earthquake kits, can enhance resilience and save lives during disasters.

• These programs are often low-cost and implemented by NGOs, but may struggle in isolated rural areas.

• While they improve community readiness, they do not prevent property damage.

Loss Modification Strategies

Emergency and Long-Term Aid

• Short-term emergency aid includes search and rescue operations, followed by the provision of food, water, and shelter to reduce immediate death tolls.

• Long-term aid focuses on reconstruction efforts that incorporate resilience-building measures, though it often faces high costs and media attention wanes quickly after disasters.

• Insurance can help individuals recover economically, but many in developing countries lack coverage, limiting their recovery options.Additionally, international organizations play a crucial role in coordinating both short-term and long-term responses, ensuring that aid reaches those in need effectively and efficiently.