DRR 12 - MIDTERMS - Earthquake and Earthquake Hazards PDF

DRR 12 - MIDTERMS ○​ Fastest seismic waves ○​ Travel through solids, liquids, and gases LESSON 1 - Earthquake and Earthquake Hazards ○...

DRR 12 - MIDTERMS ○​ Fastest seismic waves ○​ Travel through solids, liquids, and gases LESSON 1 - Earthquake and Earthquake Hazards ○​ Push-pull (compressional) motion ​ Secondary Waves (S-Waves): I. Earthquake Basics ○​ Slower than P-waves ○​ Travel only through solids An earthquake is a sudden ground movement caused by the ○​ Side-to-side (shear) motion release of elastic energy stored in rocks, generating seismic waves. B. Surface Waves A. Causes of Earthquakes ​ Love Waves: ○​ Move the ground side-to-side ​ Sudden release of energy along fault lines ○​ Named after Augustus Edward Hough ​ Volcanic activity Love ​ Human-induced activities (e.g., mining, ​ Rayleigh Waves: reservoir-induced seismicity) ○​ Rolling motion similar to ocean waves ○​ Named after Lord Rayleigh B. Parts of an Earthquake ​ Focus (Hypocenter): The point within the Earth where the earthquake originates. It is the source IV. Potential Earthquake Hazards of seismic waves. ​ Epicenter: The point on the Earth’s surface A. Ground Shaking directly above the focus. It is typically the location where the strongest shaking is felt. ​ Direct result of seismic waves ​ Fault Plane: The surface along which the slip or ​ Can cause buildings and structures to collapse displacement occurs. ​ Seismic Waves: Energy waves that radiate from B. Ground Rupture the focus, causing ground shaking. ​ Aftershocks: Smaller earthquakes that follow the ​ Occurs when the Earth's surface breaks along a main shock, usually occurring in the same area. 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 II. Types of Faults disturbances ​ Normal Faults: Caused by tension, where the crust Stages of Tsunami Formation: is pulled apart. ​ Reverse (Thrust) Faults: Caused by compression, 1.​ Initiation: Displacement of ocean water triggers where the crust is pushed together. wave formation. ​ Strike-Slip Faults: Caused by shear stress, where 2.​ Split: Waves split into distant and local tsunamis. plates slide horizontally past each other. 3.​ Amplification: Wave heights increase as they approach shore. 4.​ Runup: Waves hit the shore with accumulating force. III. Seismic Waves Signs of an Impending Tsunami: A. Body Waves ​ Ground shaking near a body of water ​ Primary Waves (P-Waves): ​ Unusual sea-level changes (receding shoreline)  ​ Rumbling sounds from incoming waves ​ Vent: Opening through which magma, gas, and ash escape to the surface. F. Landslides ​ Crater: Bowl-shaped depression at the summit of the volcano. ​ Downward movement of rock, debris, or earth on ​ Caldera: Large depression formed when a volcano slopes collapses after an eruption. ​ Triggered by earthquake shaking ​ Conduit (Pipe): Pathway for magma to travel from the chamber to the surface. Factors Influencing Landslides: ​ Lava Flow: Stream of molten rock that pours out during an eruption. ​ Steep slopes ​ Ash Cloud: Cloud of volcanic ash and gases ​ Weak slope materials released into the atmosphere. ​ Rock weathering ​ Flank: Side of the volcano where secondary vents ​ Overloading on slopes can form. 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. III. Classification of Volcanoes VI. Earthquake Preparedness (PHIVOLCS Guidelines) A. By Composition and Structure ​ Develop an emergency plan ​ Shield Volcanoes: ​ Secure heavy furniture and appliances ○​ Broad, gently sloping sides ​ Prepare an emergency kit with essentials ○​ Built from low-viscosity basaltic lava ​ Participate in earthquake drills ○​ Example: Mauna Loa (Hawaii) ​ Stay informed with official alerts and warnings ​ Stratovolcanoes (Composite Volcanoes): ○​ Steep, conical shape with alternating layers of lava and pyroclastic material LESSON 2: Volcano Hazards ○​ Explosive eruptions ○​ Example: Mount Fuji (Japan), Mount I. Introduction to Volcano Mayon (Philippines) ​ Cinder Cone Volcanoes: A volcano is an opening in the Earth's surface through ○​ Steep-sided, small volcanoes formed from which molten rock (magma), volcanic gases, ash, and other pyroclastic fragments materials are ejected. Volcanoes form when magma from ○​ Short-lived eruptions beneath the Earth's crust rises to the surface, often ○​ Example: Parícutin (Mexico) occurring at tectonic plate boundaries or over hotspots. ​ Lava Domes: ○​ Formed from slow-moving, viscous lava ○​ Can collapse and cause pyroclastic flows ○​ Example: Mount St. Helens Lava Dome II. Parts of a Volcano (USA) ​ Magma Chamber: Underground reservoir where B. By Activity magma accumulates. ​ Active Volcano: Currently erupting or showing signs of unrest.  ​ Dormant Volcano: Not currently erupting but VI. Monitoring and Early Warning Systems could erupt in the future. ​ Extinct Volcano: No longer has a magma supply and ​ Ground Deformation Monitoring: Detects changes is not expected to erupt. indicating magma movement. ​ Seismic Activity Monitoring: Tracks earthquakes and volcanic tremors. ​ Gas Emission Studies: Monitors changes in IV. Volcano Hazards volcanic gas output. ​ Remote Sensing and Satellite Imaging: Provides 1.​ Lahar (Volcanic Mudflow): continuous observation of volcanic activity. ○​ Rapid flows of water-saturated volcanic debris. ○​ Triggered by rain, melted ice, or crater lake breaches. VII. Preparedness and Mitigation Strategies ○​ Can bury communities and infrastructure. 2.​ Ashfall (Tephra Fall): ​ Develop hazard maps and identify at-risk zones. ○​ Volcanic ash ejected into the atmosphere ​ Establish evacuation routes and exclusion zones. settles over large areas. ​ Conduct community education and regular drills. ○​ Hazards: respiratory issues, contaminated ​ Strengthen structures to withstand ashfall and water, machinery damage, and roof lahars. collapse. ​ Use early warning systems to alert communities. 3.​ Pyroclastic Flow: ○​ Fast-moving, hot mixtures of gas, ash, and volcanic rock. VIII. Case Studies of Significant Volcanic Events ○​ Speeds up to 700 km/h and temperatures over 800°C. ​ Mount Pinatubo (1991, Philippines): Massive ○​ Highly destructive to life and property. eruption with global climatic effects. 4.​ Ballistic Projectiles: ​ Mount St. Helens (1980, USA): Pyroclastic flows ○​ Large volcanic rocks ejected during and significant property damage. explosive eruptions. ​ Krakatoa (1883, Indonesia): Triggered ○​ Can travel several kilometers from the devastating tsunamis and global temperature drop. volcano. 5.​ Volcanic Gas: ○​ Emissions include CO₂, SO₂, and H₂S. ○​ Can cause respiratory problems, acid rain, IX. Health and Environmental Impacts and fatalities in high concentrations. 6.​ Lava Flow: ​ Respiratory issues from ash inhalation. ○​ Streams of molten rock that destroy ​ Contaminated water sources and agricultural everything in their path. damage. ○​ Usually slow-moving but cause irreversible ​ Long-term climate effects due to volcanic aerosols. 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. GP2 12 - MIDTERMS Solution: Φ = (3.0 C)/(8.85 × 10⁻¹² C²/N·m²) ≈ 3.39 × 10¹¹ Nm²/C I. Electric Flux A. Definition III. Electric Potential Energy (U) ​ Electric flux (Φ) measures the number of electric field lines passing through a given surface. A. Definition ​ Mathematically: Φ = E · A · cos(θ) ○​ E: Electric field strength (N/C) ​ Energy stored due to the position of a charge in an ○​ A: Area of the surface (m²) electric field. ○​ θ: Angle between the electric field and ​ Formula: U = k(q₁q₂)/r the normal (perpendicular) to the surface ○​ k: Coulomb's constant (9 × 10⁹ N·m²/C²) ​ Maximum flux: Occurs when the surface is ○​ q₁, q₂: Charges (C) perpendicular to the field (θ = 0°). ○​ r: Distance between charges (m) ​ Zero flux: Occurs when the surface is parallel to the field (θ = 90°). B. Concepts B. Importance ​ Field does positive work on charge. U decreases. ​ Field does negative work on charge. U increases. ​ Describes how electric fields interact with surfaces. C. Work-Energy Principle ​ Helps calculate the strength of the field passing ​ Moving a charge in an electric field involves work through an area. that changes the system’s potential energy. C. Sample Problem D. Sample Problem Example: Calculate the electric flux through a 1 m² surface Example: Calculate the potential energy between charges with an electric field of 1 N/C perpendicular to the +5.00 C and +7.00 C separated by 1.00 m.​ surface.​ Solution: U = (9 × 10⁹)(5.00)(7.00)/1.00 ≈ 3.15 × 10¹¹ J Solution: Φ = (1 N/C)(1 m²)cos(0°) = 1 Nm²/C IV. Electric Potential (V) II. Gauss’s Law A. Definition A. Definition ​ Electric potential (V) is the potential energy per ​ Gauss’s Law relates the electric flux through a unit charge. closed surface to the charge enclosed. ​ Formula: V = U/q = k(q)/r ​ Formula: Φ = Q_enc/ε₀ ○​ Unit: Volt (V) = Joule/Coulomb (J/C) ○​ Q_enc: Total charge enclosed (C) ○​ ε₀: Permittivity of free space (≈ 8.85 × B. Key Points 10⁻¹² C²/N·m²) ​ Scalar quantity. B. Gaussian Surfaces ​ Zero potential at infinity. ​ High potential near positive charges; low near ​ Spherical surface: Used for point charges and negative charges. spherical charge distributions. ​ Cylindrical surface: Used for line charges. C. Potential Difference (Voltage) ​ Planar surface: Used for infinite plane charges. ​ Work done in moving a unit charge between two C. Applications points. ​ Formula: ΔV = W/q ​ Calculating electric fields for symmetric charge distributions. D. Sample Problem ​ Understanding charge distribution on conductors. Example: Calculate the potential at a point 0.5 m from a D. Sample Problem +2.00 C charge.​ Solution: V = (9 × 10⁹)(2.00)/0.5 ≈ 3.60 × 10¹⁰ V Example: Find the electric flux through a closed surface enclosing a charge of +3.0 C.​ V. Relationships and Applications Solution:​ Formula: V = kq/r​ A. Relationship Between Concepts Given: k = 8.99 × 10⁹ Nm²/C², q = +3.00 C ​ Electric field (E): Gradient of the electric ​ At 1.00 m:​ potential (E = -dV/dr). V₁ = (8.99 × 10⁹ × 3.00) / 1.00 = 2.70 × 10¹⁰ ​ Potential energy (U): Related to potential by U = V qV. ​ At 3.00 m:​ ​ Flux and Gauss’s Law: Connect field lines to V₃ = (8.99 × 10⁹ × 3.00) / 3.00 = 9.00 × 10⁹ V​ charge distribution. Potential difference:​ V31 = V₃ - V₁ = 9.00 × 10⁹ - 2.70 × 10¹⁰ = B. Practical Applications -1.80 × 10¹⁰ V ​ Design of capacitors. ​ Insulation and shielding in electrical systems. ​ Analyzing electric fields around conductors. Sample Problem 2: Problem: Two charges q₁ = -3.00 × 10⁻⁶ C and q₂ = +5.00 × 10⁻⁶ C are 5.00 m apart. If q₂ moves to a point A, 2.50 m VI. Summary away from q₁, how much work is done? ​ Electric Flux: Measures field lines through a Solution:​ surface. Formula: W = q(VA - VB) ​ Gauss’s Law: Relates flux to enclosed charge. ​ Electric Potential Energy: Energy due to charge ​ VA = kq₁/2.50 position. ​ VB = kq₁/5.00​ ​ Electric Potential: Energy per unit charge; Find VA - VB, then substitute into the work measured in volts. formula. ​ These concepts are interconnected and fundamental to understanding electrostatics. Sample Problem 5: Concept of Potential Difference Problem: A charge of 6 × 10⁻⁷ C is transferred from infinity to point B. Work done: 1.2 × 10⁻⁵ J. Find the ​ Electric Potential (V): The electric potential at a potential at B. point is the work done to bring a unit positive charge from infinity (zero potential energy) to Solution:​ that point. Formula: V = U/q​ ​ Equation:​ V = (1.2 × 10⁻⁵) / (6 × 10⁻⁷) = 20 V V = U/q​ where: ○​ V: electric potential (volts, V) Sample Problem 6: ○​ U: potential energy (joules, J) ○​ q: charge (coulombs, C) Problem: A stationary proton moves from A (450.0 V) to B ​ Potential Difference (Vab): The work done by the (125 V). electric force to move a unit positive charge from point A to point B. (a) Work done by electric force:​ ​ Formula:​ Formula: W = q(VB - VA)​ Vab = VB - VA W = (1.60 × 10⁻¹⁹ C)(125 - 450) = -5.20 × 10⁻¹⁷ J ​ Key Point: Potential difference is independent of the path taken. (b) Speed at point B:​ Use: K.E. = q(VA - VB) = (1/2)mv²​ Solve for v. Sample Problems & Solutions Sample Problem 1: Electron Volt (eV) Problem: Calculate the electric potential difference ​ Definition: Energy gained by an electron moving between 1.00 m and 3.00 m from a +3.00 C charge. through a potential difference of 1 V.  ​ Conversion:​ 1 eV = 1.60 × 10⁻¹⁹ J Sample Problem 9: Problem: Convert 3.15 × 10¹¹ J to eV. Solution:​ Formula: E(eV) = Energy (J) / (1.60 × 10⁻¹⁹ J/eV)​ E(eV) = (3.15 × 10¹¹) / (1.60 × 10⁻¹⁹) = 1.97 × 10³⁰ eV Quick Reference Formulas: ​ V = U/q ​ V = kq/r ​ VBA = VB - VA ​ W = q(VB - VA) ​ 1 eV = 1.60 × 10⁻¹⁹ J ​ K.E. = (1/2)mv²