Earthquake and Volcano Hazards PDF

DRR 12 - MIDTERMS LESSON 1 - Earthquake and Earthquake Hazards I. Earthquake Basics An earthquake is a sudden ground movement caused by the release of elastic energy stored in rocks, generating seismic waves. A. Causes of Earthquakes ​ Sudden release of energy along fault lines ​ Vo...

DRR 12 - MIDTERMS LESSON 1 - Earthquake and Earthquake Hazards I. Earthquake Basics An earthquake is a sudden ground movement caused by the release of elastic energy stored in rocks, generating seismic waves. A. Causes of Earthquakes ​ Sudden release of energy along fault lines ​ Volcanic activity ​ Human-induced activities (e.g., mining, reservoir-induced seismicity) B. Parts of an Earthquake ​ Focus (Hypocenter): The point within the Earth where the earthquake originates. It is the source of seismic waves. ​ Epicenter: The point on the Earth’s surface directly above the focus. It is typically the location where the strongest shaking is felt. ​ Fault Plane: The surface along which the slip or displacement occurs. ​ Seismic Waves: Energy waves that radiate from the focus, causing ground shaking. ​ Aftershocks: Smaller earthquakes that follow the main shock, usually occurring in the same area. II. Types of Faults ​ Normal Faults: Caused by tension, where the crust is pulled apart. ​ Reverse (Thrust) Faults: Caused by compression, where the crust is pushed together. ​ Strike-Slip Faults: Caused by shear stress, where plates slide horizontally past each other. III. Seismic Waves A. Body Waves ​ Primary Waves (P-Waves): ○​ Fastest seismic waves ○​ Travel through solids, liquids, and gases ○​ Push-pull (compressional) motion ​ Secondary Waves (S-Waves): ○​ Slower than P-waves ○​ Travel only through solids  ○​ Side-to-side (shear) motion B. Surface Waves ​ Love Waves: ○​ Move the ground side-to-side ○​ Named after Augustus Edward Hough Love ​ Rayleigh Waves: ○​ Rolling motion similar to ocean waves ○​ Named after Lord Rayleigh IV. Potential Earthquake Hazards A. Ground Shaking ​ Direct result of seismic waves ​ Can cause buildings and structures to collapse B. Ground Rupture ​ Occurs when the Earth's surface breaks along a fault line ​ Common along zones of weakness C. Liquefaction ​ Saturated soil loses strength and behaves like a liquid ​ Common signs: water leaking from the ground D. Ground Subsidence ​ Downward sinking or settling of the ground surface E. Tsunami ​ Series of giant waves caused by underwater disturbances Stages of Tsunami Formation: 1.​ Initiation: Displacement of ocean water triggers wave formation. 2.​ Split: Waves split into distant and local tsunamis. 3.​ Amplification: Wave heights increase as they approach shore. 4.​ Runup: Waves hit the shore with accumulating force. Signs of an Impending Tsunami:  ​ Ground shaking near a body of water ​ Unusual sea-level changes (receding shoreline) ​ Rumbling sounds from incoming waves F. Landslides ​ Downward movement of rock, debris, or earth on slopes ​ Triggered by earthquake shaking Factors Influencing Landslides: ​ Steep slopes ​ Weak slope materials ​ Rock weathering ​ Overloading on slopes V. Measuring Earthquakes A. Magnitude: ​ Measures the energy released at the source of the earthquake. ​ Quantified using scales like the Richter or Moment Magnitude Scale. B. Intensity: ​ Measures the effects and how strong the shaking feels at specific locations. ​ Commonly measured using the Modified Mercalli Intensity (MMI) scale. VI. Earthquake Preparedness (PHIVOLCS Guidelines) ​ Develop an emergency plan ​ Secure heavy furniture and appliances ​ Prepare an emergency kit with essentials ​ Participate in earthquake drills ​ Stay informed with official alerts and warnings LESSON 2: Volcano Hazards I. Introduction to Volcano A volcano is an opening in the Earth's surface through which molten rock (magma), volcanic gases, ash, and other materials are ejected. Volcanoes form when magma from beneath the Earth's crust rises to the surface, often occurring at tectonic plate boundaries or over hotspots. II. Parts of a Volcano ​ Magma Chamber: Underground reservoir where magma accumulates. ​ Vent: Opening through which magma, gas, and ash escape to the surface. ​ Crater: Bowl-shaped depression at the summit of the volcano. ​ Caldera: Large depression formed when a volcano collapses after an eruption. ​ Conduit (Pipe): Pathway for magma to travel from the chamber to the surface. ​ Lava Flow: Stream of molten rock that pours out during an eruption. ​ Ash Cloud: Cloud of volcanic ash and gases released into the atmosphere. ​ Flank: Side of the volcano where secondary vents can form. III. Classification of Volcanoes A. By Composition and Structure ​ Shield Volcanoes: ○​ Broad, gently sloping sides ○​ Built from low-viscosity basaltic lava ○​ Example: Mauna Loa (Hawaii) ​ Stratovolcanoes (Composite Volcanoes): ○​ Steep, conical shape with alternating layers of lava and pyroclastic material ○​ Explosive eruptions ○​ Example: Mount Fuji (Japan), Mount Mayon (Philippines) ​ Cinder Cone Volcanoes: ○​ Steep-sided, small volcanoes formed from pyroclastic fragments ○​ Short-lived eruptions ○​ Example: Parícutin (Mexico) ​ Lava Domes: ○​ Formed from slow-moving, viscous lava ○​ Can collapse and cause pyroclastic flows ○​ Example: Mount St. Helens Lava Dome (USA) B. By Activity ​ Active Volcano: Currently erupting or showing signs of unrest. ​ Dormant Volcano: Not currently erupting but could erupt in the future. ​ Extinct Volcano: No longer has a magma supply and is not expected to erupt. IV. Volcano Hazards 1.​ Lahar (Volcanic Mudflow): ○​ Rapid flows of water-saturated volcanic debris. ○​ Triggered by rain, melted ice, or crater lake breaches. ○​ Can bury communities and infrastructure. 2.​ Ashfall (Tephra Fall): ○​ Volcanic ash ejected into the atmosphere settles over large areas. ○​ Hazards: respiratory issues, contaminated water, machinery damage, and roof collapse. 3.​ Pyroclastic Flow: ○​ Fast-moving, hot mixtures of gas, ash, and volcanic rock. ○​ Speeds up to 700 km/h and temperatures over 800°C. ○​ Highly destructive to life and property. 4.​ Ballistic Projectiles: ○​ Large volcanic rocks ejected during explosive eruptions. ○​ Can travel several kilometers from the volcano. 5.​ Volcanic Gas: ○​ Emissions include CO₂, SO₂, and H₂S. ○​ Can cause respiratory problems, acid rain, and fatalities in high concentrations. 6.​ Lava Flow: ○​ Streams of molten rock that destroy everything in their path. ○​ Usually slow-moving but cause irreversible damage. V. Signs of an Impending Eruption ​ Increased Seismic Activity: More frequent volcanic earthquakes indicating rising magma. ​ Ground Deformation: Swelling or sinking of the volcano's surface. ​ Gas Emissions: Elevated release of volcanic gases like SO₂ and CO₂. ​ Changes in Temperature: Rising temperatures around the crater or vents. ​ Small Steam or Ash Explosions: Precursors to a larger eruption. ​ Unusual Animal Behavior: Animals may flee the area before an eruption. VI. Monitoring and Early Warning Systems ​ Ground Deformation Monitoring: Detects changes indicating magma movement. ​ Seismic Activity Monitoring: Tracks earthquakes and volcanic tremors. ​ Gas Emission Studies: Monitors changes in volcanic gas output. ​ Remote Sensing and Satellite Imaging: Provides continuous observation of volcanic activity. VII. Preparedness and Mitigation Strategies ​ Develop hazard maps and identify at-risk zones. ​ Establish evacuation routes and exclusion zones. ​ Conduct community education and regular drills. ​ Strengthen structures to withstand ashfall and lahars. ​ Use early warning systems to alert communities. VIII. Case Studies of Significant Volcanic Events ​ Mount Pinatubo (1991, Philippines): Massive eruption with global climatic effects. ​ Mount St. Helens (1980, USA): Pyroclastic flows and significant property damage. ​ Krakatoa (1883, Indonesia): Triggered devastating tsunamis and global temperature drop. IX. Health and Environmental Impacts ​ Respiratory issues from ash inhalation. ​ Contaminated water sources and agricultural damage. ​ Long-term climate effects due to volcanic aerosols. GP2 12 - MIDTERMS I. Electric Flux A. Definition ​ Electric flux (Φ) measures the number of electric field lines passing through a given surface. ​ Mathematically: Φ = E · A · cos(θ) ○​ E: Electric field strength (N/C) ○​ A: Area of the surface (m²) ○​ θ: Angle between the electric field and the normal (perpendicular) to the surface ​ Maximum flux: Occurs when the surface is perpendicular to the field (θ = 0°). ​ Zero flux: Occurs when the surface is parallel to the field (θ = 90°). B. Importance ​ Describes how electric fields interact with surfaces. ​ Helps calculate the strength of the field passing through an area. C. Sample Problem Example: Calculate the electric flux through a 1 m² surface with an electric field of 1 N/C perpendicular to the surface.​ Solution: Φ = (1 N/C)(1 m²)cos(0°) = 1 Nm²/C II. Gauss’s Law A. Definition ​ Gauss’s Law relates the electric flux through a closed surface to the charge enclosed. ​ Formula: Φ = Q_enc/ε₀ ○​ Q_enc: Total charge enclosed (C) ○​ ε₀: Permittivity of free space (≈ 8.85 × 10⁻¹² C²/N·m²) B. Gaussian Surfaces ​ Spherical surface: Used for point charges and spherical charge distributions. ​ Cylindrical surface: Used for line charges. ​ Planar surface: Used for infinite plane charges. C. Applications ​ Calculating electric fields for symmetric charge distributions. ​ Understanding charge distribution on conductors. D. Sample Problem Example: Find the electric flux through a closed surface enclosing a charge of +3.0 C.​ Solution: Φ = (3.0 C)/(8.85 × 10⁻¹² C²/N·m²) ≈ 3.39 × 10¹¹ Nm²/C III. Electric Potential Energy (U) A. Definition ​ Energy stored due to the position of a charge in an electric field. ​ Formula: U = k(q₁q₂)/r ○​ k: Coulomb's constant (8.99 × 10⁹ N·m²/C²) ○​ q₁, q₂: Charges (C) ○​ r: Distance between charges (m) B. Concepts ​ Positive U: Like charges repel (work done to bring them together). ​ Negative U: Opposite charges attract (energy released when they come closer). C. Work-Energy Principle ​ Moving a charge in an electric field involves work that changes the system’s potential energy. D. Sample Problem Example: Calculate the potential energy between charges +5.00 C and +7.00 C separated by 1.00 m.​ Solution: U = (8.99 × 10⁹)(5.00)(7.00)/1.00 ≈ 3.15 × 10¹¹ J IV. Electric Potential (V) A. Definition ​ Electric potential (V) is the potential energy per unit charge. ​ Formula: V = U/q = k(q)/r ○​ Unit: Volt (V) = Joule/Coulomb (J/C) B. Key Points ​ Scalar quantity. ​ Zero potential at infinity. ​ High potential near positive charges; low near negative charges. C. Potential Difference (Voltage) ​ Work done in moving a unit charge between two points. ​ Formula: ΔV = W/q D. Sample Problem Example: Calculate the potential at a point 0.5 m from a +2.00 C charge.​ Solution: V = (8.99 × 10⁹)(2.00)/0.5 ≈ 3.60 × 10¹⁰ V V. Relationships and Applications A. Relationship Between Concepts ​ Electric field (E): Gradient of the electric potential (E = -dV/dr). ​ Potential energy (U): Related to potential by U = qV. ​ Flux and Gauss’s Law: Connect field lines to charge distribution. B. Practical Applications ​ Design of capacitors. ​ Insulation and shielding in electrical systems. ​ Analyzing electric fields around conductors. VI. Summary ​ Electric Flux: Measures field lines through a surface. ​ Gauss’s Law: Relates flux to enclosed charge. ​ Electric Potential Energy: Energy due to charge position. ​ Electric Potential: Energy per unit charge; measured in volts. ​ These concepts are interconnected and fundamental to understanding electrostatics.