Earthquakes: Causes, Impact, and History

Earthquake Module 1: Origin of Earthquakes and Faulting

• An earthquake is a sudden shaking of Earth's surface caused by tectonic plate movement beneath the crust.

Why Earthquakes Are Devastating

• Earthquakes cause destruction in seconds.
• Buildings collapse and roads crack.
• Fires may start.
• People get injured or die.
• Damage spreads quickly.
• Communities struggle to recover after an earthquake.
• Earthquakes can trigger tsunamis and landslides.

Economic Impact of Earthquakes

• Earthquakes destroy homes, businesses, and infrastructure.
• Governments spend billions on rebuilding.
• Job losses occur as businesses shut down.
• Economic slowdown affects struggling industries.
• Reconstruction can take years.

Major Earthquakes in History

• 1975 Tangshan Earthquake: One of the deadliest earthquakes in history, killed about 200,000 people in China.
• 1994 Northridge Earthquake: In California, caused 57 deaths and cost approximately $42 billion in economic losses.
• 1995 Kobe Earthquake: In Japan, resulted in approximately 6,000 fatalities and economic losses exceeding $120 billion.
• 1996 Izmit Earthquake: A 7.4 magnitude earthquake struck Izmit, Turkey, killing around 20,000 people and causing $12 billion in damages.
• 1999 Chi-Chi Earthquake: A 7.6 magnitude earthquake struck Taiwan, causing an estimated $8 billion in losses.
• 2006 Gujarat Earthquake: A 5.5 magnitude earthquake in India, led to about 18,000 deaths and destroyed 330,000 buildings.
• 2008 Sichuan Earthquake: One of the most devastating earthquakes in modern history in China, leaving 88,000 people dead or missing, with economic losses estimated at $29 billion.
• 2011 Tōhoku Earthquake and Tsunami: A 9.1 magnitude earthquake in Japan triggered a massive tsunami, causing over 8,700 deaths and $235-$305 billion in costs.

Seismic Loss Estimation & Economic Impact of Earthquakes

• Seismic Loss Estimation: Evaluates potential damages caused by seismic events, assessing seismic losses and managing financial/economic risks.
• Performance-Based Earthquake Engineering (PBEE): Seeks to improve seismic risk decision-making through transparent, scientific, and informative assessment and design methods.

Consequences and Effects of Earthquakes

• Primary/Direct Effects: Appear immediately after and include social and physical damage.
• Secondary/Indirect Effects: Take into account the system-wide impact of flow losses through interindustry relationships and economic sectors.
• 'Total impact' refers to the summation of direct and indirect losses.
• An economy is divided into three sectors:
• Primary Sector: Deals with raw materials (e.g., farming, fishing, mining).
• Secondary Sector: Involves manufacturing (e.g. factories producing goods).
• Tertiary Sector: Provides services (e.g., banking, retail, healthcare).
• Performance-Based Earthquake Engineering (PBEE): A structured framework evaluates the potential effects on buildings and infrastructure, helping engineers and decision-makers understand seismic hazards, predict structural response, and assess damage and economic losses.

The PBEE process

• Can be expressed in terms of a four-step analysis, including:
• Hazard Analysis results in Intensity Measures (IMS) for the facility under study.
• Structural Analysis gives the Engineering Demand Parameters (EDPs) required for damage analysis
• Damage Analysis compares the EDPs with the Damage Measure to decide the failure of the facility.
• Loss Analysis evaluates the occurrence of Decision Variables (DVs) due to failures.

Primary Effects from Earthquakes

• Social or Human Effects: Fatalities, injuries, loss of income/employment, homelessness.
• Physical Effects: Ground deformation/loss, collapse/structural damage to buildings/infrastructure, non-structural damage.
• Economic Effects: Disruption of business, loss of productive workforce, disruptions of communications, cost of response/relief.

Secondary Effects from Earthquakes

• Social or Human Effects: Disease/disability, psychological impact, loss of social cohesion, political unrest.
• Physical Effects: Reduced seismic capacity of unrepaired structures, progressive deterioration of unrepaired buildings/infrastructure.
• Economic Effects: Losses suffered by insurance industry/markets, increased prices, losses of markets/trade opportunities.

Structural Failures: Overall Failure

• Moment Frame in Longitudinal Direction, Shear Walls at Each End in Short Direction: The Structural system approved as a major structural category to resist earthquakes influenced building codes.
• The moment frame-shear wall combination: The end shear walls will take care of the earth force component in the short direction while the moment frame will resist the longitudinal component acting in the longitudinal direction of the structure.

Structural Failures: 1994 Northridge Earthquake

• Kaiser Office Building: A shear wall collapsed in the Kaiser Permanente Office Building.
• Champagne Towers: An upscale high-rise apartment building overlooking the Santa Monica Bay in Southern California was built utilizing a similar system with reinforced-concrete moment frames acting in the long direction of the structure.

Concepts, Terminology, and Source of Earthquakes

• Specific Gravity:
• Earth's crust: 2.7-3.0
• Mantle (inner periphery): 5.7
• Core (periphery): 9.7
• Center: 12.3
• Isostasy: The earth's crust floats on the surface of the mantle.

Orogenic Movements and Crust Convection (Conveyor Belt)

• Orogenic movements and crust convection are mainly responsible for mountain building and valley forming in other words, the constant changes affecting the surface of the earth.
• Alfred Wegener asserted that continents were connected and then drifted away from each other.
• Fossil evidence has substantiated the fact that continents were once one massive piece.
• Ocean floor fissures and left and right movements like a giant conveyor belt, move continents that float on the viscous mantle.

Volcanoes

• A volcano is an opening in the earth's crust through which lava, volcanic ash, and gases escape.
• Volcanoes are classified as active, dormant, and extinct.
• Volcanoes form in two settings:
• Oceanic plate descends below another oceanic plate
• Oceanic plate descends below a continental plate.
• Ocean-ocean subduction produces an island arc volcano.
• The Sunset Crater volcano eruption coupled with strong ground motion caused panic among the native population in Flagstaff and the surrounding areas of Arizona.
• In northern California, Mount Shasta bombarded the neighboring region with boulders accompanied by severe ground motion.
• The 1812 New Madrid earthquake in Missouri is considered the largest earthquake in a low seismicity area.
• The Mississippi constantly erodes the land mass lightening earths crust

Summary of main sources of earthquake:

• Orogenic movements such as mountain building
• Subduction and plate convection followed by geothermal mechanical disturbances
• Volcanic activity
• Land erosion

Module 2: Origin of Earthquake and Faulting

• Earthquake - quake, tremor, or temblor.
• It is described as any seismic event.
• Originates at a considerable depth below the surface of the earth.
• The focus is a point inside the earth where the earthquake started. The point on the surface of the earth directly above the focus is called the epicenter.
• Seismology - The study of causes, propagation, and effects of the movements of the earth's crust that result from an earthquake.

Types of Earthquake

• Earthquakes as to its origin (natural)
• Earthquakes as to the focal depth
• Artificially induced earthquakes (human activity)

Types of Earthquake - Origin

• Tectonic earthquakes: Caused by the sudden slippage along a fault or dislocation line in the outer part of the earth.
• Volcanic earthquakes: Associated with volcanic eruption or subterranean movement of magma.

Types of Earthquake - Depth

• Shallow Earthquakes:
• The majority of earthquakes are of shallow origin.
• Most tectonic earthquakes have originated at depths of no more than sixty (60) kilometers.
• Intermediate Earthquakes: Have focal depths from 70 km – 300 km (12%).
• Deep Earthquakes:
• Have focal Depths greater than 300 km (depths ranging from 300-700 km).
• Commonly occur in patterns called Benioff zones like Japan, Vanuatu, Tonga, and Alaska, and are normally associated with deep ocean trenches (6%).

Types of Earthquake - Human

• Collapse of caverns or mine workings
• Injection of fluids into deep wells
• Detonation of large underground nuclear explosions
• Excavations of mines
• Quarry blasting
• Filling of large reservoirs

Theories of Earthquake

• Continental Drift Theory: Continents were once joined together in a single landmass called Pangaea and have since drifted apart.
• Theory of Plate tectonics: Concerns the divided plates that move and interact, causing earthquakes, volcanoes, and mountain formation
• Elastic Rebound Theory: Earthquake occurs when stress builds up in rocks along faults, causing them to deform until they can no longer withstand the stress, and then they suddenly snap back to their original shape, releasing energy in the form of seismic waves.
• The Lithosphere is the Earths solid, rocky outer layer.

Creation and Destruction of Lithosphere

• Creation of Lithosphere:
• Mid-Ocean Ridges – tectonic plates pull apart and molten material escapes as a subsea fissure eruption.
• Destruction of Lithosphere:
• Subduction Zones – where lithospheric plates descend into the mantle and are assimilated into the mantle.
• A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere.

Major tectonic Plates

• African Plate
• Antarctic Plate
• Australian Plate
• Eurasian Plate
• North American Plate
• Pacific Plate
• South American Plate

Minor tectonic Plates

• Arabian Plate
• Caribbean Plate
• Cocos Plate
• Indian Plate
• Juan de Fuca Plate
• Nazca Plate
• Philippine Plate
• Scotia Plate

Movement of Tectonic Plates

• According to geologists, the movement of tectonic plates is related to convection currents in the Earth's mantle.
• Convection currents is characterized by rising hot mantle material and sinking colder material.
• It is the primary driver of plate tectonic movement, influencing tectonic processes such as earthquakes and volcanic eruptions.

Mantle Convection

• Mantle Convection (diagram)

Plate Boundaries

• Plates slide past each other horizontally Transform Boundaries (San Andreas Fault in California).
• Plates move towards each other - Convergent Boundaries.
• Plates move apart - Divergent Boundaires.
• Well-defined Boundariesare boundaries that can be easily plotted on a map at a reasonably accurate location

Famous Faults in the World

• San Andreas Fault (California, USA)
• Hayward Fault (California, USA)
• North Anatolian Fault (Turkey)
• San Jacinto Fault (California, USA)
• East African Rift System (East Africa)

Examples of Well-defined Plate Boundaries

• Mid-ocean ridges.
• Continental Rift.
• Island Arc.
• Ocean trenches.
• Transform faults.
• Mid-ocean ridges are divergent boundaries where new lithosphere is created as plates move apart.
• They are characterized by underwater volcanic activities and shallow earthquakes.
• Transform faults are boundaries where plates slide past each other horizontally.
• They are marked by shallow earthquakes and can offset features like rivers and ridges.
• Poorly-defined Boundaries = Lack clear topographic expression or have ambiguous lithospheric discontinuities.
• Boundaries are difficult to pinpoint precisely and can only be plotted on a map with approximate locations.

Faulting

• When enormous stresses build and push large intact rock masses beyond their yield limit, faulting of the surface is likely to occur.
• A fault is a fracture in the Earth's crust along which movement has occurred.

Main Types of Faults

• Normal Fault - The hanging wall (the block of rock above the fault plane) moves downward compared to the footwall.
• Reverse Fault - The hanging wall moves upward compared to the footwall.
• Strike-Slip Fault - The movement is primarily horizontal, with minimal vertical displacement.

Famous Faults in the World

• San Andreas Fault (California, USA)
• Hayward Fault (California, USA)
• North Anatolian Fault (Turkey)
• San Jacinto Fault (California, USA)
• East African Rift System (East Africa)

Module 3: Active Faults and Seismic Zones of the Philippines

• The Philippine archipelago is divided into two seismic zones only:
• Zone 2 - Sulu, Tawi-Tawi, and Palawan
• Zone 4 - the rest of the country

Role of Tectonic Plates

• Three Major Plates:
• Philippine Sea Plate
• Eurasian Plate
• Indo-Australian Plate
• FAULT LINE - It is the movement of masses of rock has displaced parts of the earth's crust.

5 Major Active Faults in the Philippines

• MARIKINA VALLEY FAULT
• WESTERN PHILIPPINE FAULT
• EASTERN PHILIPPINE FAULT
• SOUTHERN OF MINDANAO FAULT
• CENTRAL PHILIPPINE FAULT

Remarkable Examples of Faults

• CHUZON SUPERMARKET (April 22, 2019, Magnitude of 6.1, Santa Catalina De Alejandria Parish Church)

MARIKINA VALLEY FAULT

• Poses a significant earthquake threat, especially to densely populated areas.
• It is a major active fault system in the Philippines, running through Metro Manila and nearby provinces.
  • West Valley Fault (WVF) – Capable of generating a Magnitude 7.2 earthquake.
  • EAST VALLEY FAULT – Capable of generating a Magnitude 6.5 – 7 earthquake.

EARTHQUAKE RISK (THE BIG ONE)

• Studies by PHIVOLCS, JICA, and MMDA indicate that if the West Valley Fault moves, it could cause:
  • A Magnitude 7.2 earthquake
  • Massive destruction in Metro Manila and nearby areas
  • Deaths ranging from 30,000to 50,000+ people
  • Infrastructure collapse, fires, landslides, and liquefaction.

EASTERN PHILIPPINE FAULT

• It is an active fault line located in the Philippine Sea.
  • EXAMPLE – 1879 Surigao earthquake
    • June 30, 1879
    • 7.4 magnitude
    • 100 km long
    • No casualties

SOUTHERN MINDANAO FAULT

• It runs across the Celebes Sea and Moro Gulf.
  • 1976 MINDANAO EARTHUQAKE
    • August 17, 1976
    • Moro gulf
    • 8.0 magnitude
    • Estimated 5,000 to 8,000 fatalities

FAULT

• The Central Philippine Fault Zone triggers fault creep, slides, and quakes from the north to Northern Davao.
  • 1990 LUZON EARTHQUAKE
    • July 16, 1990
    • 7.8 magnitude
    • Dingalan, Aurora to Kapaya Nueva Vizcaya
    • Estimated 1,621 people were killed

SEISMIC ZONE

• Zone Classification
• Seismic Hazard Mapping
• Building Codes and Standards
• Ground Shaking Potential

HISTORICAL MOVEMENTS

• The fault moves approximately every 400-600 years.
• The last major movement was around 1658, meaning it is within the timeframe for another major earthquake.

WESTERN PHILIPPINE FAULT

• The Western Philippine Fault is a big crack in the Earth's crust that runs along the west side of the Philippines.
• It causes big earthquakes. Its significance in earthquake and tsunami hazards.
  • Overview of affected regions (Luzon, Mindoro, Panay, Sulu, and nearby islands).

FAULTS IN THE WESTERN PHILIPPINES

• Manila Trench (Luzon Sea):
  • Offshore trench west of Luzon.
  • Subduction zone where the Eurasian Plate is sinking beneath the Philippine Sea Plate.
  • Potential to produce Magnitude 8+ earthquakes and tsunamis
• Mindoro Fault and Mindoro Trench (Mindoro Strait):
  • Located between Mindoro and Palawan.
  • Responsible for the 1994 Mindoro Earthquake (M7.1) and tsunami
• Panay Fault and Negros Trench (Panay Gulf):
  • Runs along the western side of Negros and Panay Islands.
  • Capable of generating deep earthquakes and tsunamis.
• Sulu Trench (Sulu Sea):
  • Found west of Mindanao, near the Sulu Archipelago.
  • Subduction zone with potential for M8+ earthquakes.
  • Tsunamis may affect Palawan, Mindanao, and Sabah (Malaysia).

REGION I

• Ilocos Norte, Ilocos Sur, La Union, and Pangasinan are provinces.
  • ACTIVE FAULTS:
    • Philippine Fault Zone
    • Abra River Fault
    • West Ilocos Fault
    • Naglibacan Fault
  • TRENCHES:
    • Manila Trench
  • HAZARD LEVEL: HIGH

REGION II

• Batanes, Cagayan, Isabela, Quirino, and Nueva Vizcaya.
  • ACTIVE FAULTS:
    • Philippine Fault Zone
    • Digdig Fault
    • Cagayan Valley Fault
  • TRENCHES:
    • Philippine Trench
    • Tiburon Trench
  • HAZARD LEVEL: HIGH

REGION III

• Aurora, Bataan, Bulacan, Nueva Ecija, Pampanga, Tarlac, and Zambales.
  • ACTIVE FAULTS:
    • Philippine Fault Zone
    • San Manuel Fault
    • San Jose Fault
    • Digdig Fault
    • Gabaldon Fault
  • TRENCHES:
    • Philippine Trench
    • Manila Trench
  • HAZARD LEVEL: HIGH

REGION IV-A

• Cavite, Laguna, Batangas, Rizal, and Quezon are provinces
  • ACTIVE FAULTS:
    • Lubang-Verde Island Fault
    • Lipa Faults
    • Valley Fault System (East and West)
  • TRENCHES:
    • Philippine Trench
    • Manila Trench
    • East Luzon Trench
  • HAZARD LEVEL: MEDIUM

REGION IV-B

• Mindoro Occidental, Mindoro Oriental, Marinduque, Romblon, and Palawan are provinces.
  • ACTIVE FAULTS:
    • Philippine Fault Zone
    • Mindoro Fault
    • Marinduque Fault
    • Romblon Fault
  • TRENCHES:
    • Philippine Trench
    • Manila Trench
  • HAZARD LEVEL: HIGH

REGION V

• Albay, Camarines Norte, Camarines Sur, Catanduanes, Masbate, and Sorsogon are provinces.
  • ACTIVE FAULTS:
    • San Vicente-Linao Fault
    • San Miguel Fault
    • Hilawan Fault
    • Minas Fault
  • TRENCHES:
    • Philippine Trench
  • HAZARD LEVEL: MEDIUM

REGION VI

• Aklan, Antique, Negros Occidental, Capiz, Guimaras and Iloilo are provinces
  • Active Faults:
    • West Panay Fault
    • Central Negros Fault
  • Trench:
    • Negros Trench

REGION VII

• Central Visayas is an administrative region
  • ACTIVE FAULTS:
    • Cebu Fault System
    • Negros Fault System
    • Bohol Fault System
    • Central Cebu Fault
    • Southern Cebu Fault
  • TRENCH:
    • Negros Trench
    • East Bohol Trench

REGION VIII

• Eastern Visayas, one independent city and one highly urbanized city
  • ACTIVE FAULTS:
    • Leyte Segment ng Philippine Fault
    • Samar Segment ng Philippine Fault
  • TRENCH:
    • Philippine Trench
    • East Mindanao Trench

ARMM

• Autonomous Region in Muslim Mindanao was an autonomous region of the Philippines
  • ACTIVE FAULTS:
    • Mindanao Fault System
    • Maguindanao Fault
    • Tawi-Tawi Fault
  • TRENCH:
    • Cotabato Trench
    • Sulu Trench

REGION 9

• Zamboanga del Norte, Zamboanga del Sur, and Zamboanga Sibugay
  • Active Faults:
    • Zamboanga Fault
    • Sindangan-Cotabato Fault System
  • Trench:
    • Cotabato Trench

REGION 10

• Bukidnon, Camiguin, Lanao del Norte, Misamis Occidental, and Misamis Oriental are provinces
  • Active Faults:
    • Central Mindanao Fault
    • Tagoloan River Fault
    • Cabanglasan Fault
  • Trench:
    • Mindanao Trench

REGION 13

• Agusan del Norte, Agusan del Sur, Dinagat Islands, Surigao del Norte, and Surigao del Sur are provinces
  • Active Faults:
    • Surigao Segment of the Philippine Fault
    • Hinatuan Fault
    • Cantilan Fault
    • Lake Mainit Fault
  • TRENCHES:
    • East Mindanao Trench
    • Philippine Trench

CAR

• Cordillera Administrative Region comprises six provinces: Abra, Apayao, Benguet, Ifugao, Kalinga and Mountain Province.
  • ACTIVE FAULTS:
    • Digdig Fault
    • Abra River Fault
    • West Ilocos Fault System
    • East Cordillera Fault
  • TRENCHES:
    • Manila Trench
    • Philippine Trench

REGION 11

• Davao de Oro, Davao del Norte, Davao del Sur, Davao Oriental, and Davao Occidental are provinces
  • ACTIVE FAULTS:
    • Davao Fault System
    • Cotabato Fault System
    • Mindanao Fault
    • Tamugan Fault
    • Lacson Fault
  • TRENCHES:
    • Cotabato Trench
    • Philippine Trench
    • East Mindanao Trench

REGION 12

• South Cotabato, Cotabato, Sultan Kudarat, and Sarangani are provinces
  • ACTIVE FAULTS:
    • South Cotabato Fault
    • Cotabato Fault System
    • M'lang Fault
    • Makilala-Malungon Fault
    • Tampakan Fault
  • TRENCHES:
    • Cotabato Trench
    • Philippine Trench

MODULE 4: EARTHQUAKE MEASURMENTS

• Two main ways to measure EARTHQUAKES:
  • The engery released.
  • People felt and how much damage was done.

CHARTERISTICS OF AN EARTHQUAKE STATION

• Time
• Epicenter
• Focal depth
• Fault
• Energy Released

CAUSE OF EARTHQUAKE

• Tectonic Plate Movements
• Volcanic Activity
• Human Activities
• Faults

TECTONIC PLATE MOVEMENTS

• Convergent - Himalaya Mountains In Central Asia
• Divergent - Mid-Atlantic Ridge
• Transform - San Andreas Fault

Volcanic Activity

• Nevado del Ruiz (1985)
• Pinatubo (1991)

HUMAN ACTIVITIES

• Geothermal energy production
• Fracking for oil and natural gas
• Wastewater disposal

Faults

• Normal Fault
• Reverse Fault
• Strike-slip Fault

MEASURING EARTHQUAKES USING SEISMOGRAPHS

• A seismograph is an instrument used to detect and measure ground vibrations caused by earthquakes.
• Earthquakes produce vibrations that travel through the Earth's surface and interior.
• Records produces by seismographs are known as seismograms.

HOW SEISMOGRAPH WORKS

• A seismograph measures the relative movement between a suspended mass and the ground.
• The Stylus (pen) attached to the mass records the relative motion between the mass and the housing on a rotating drum, creating a seismogram.
• During an earthquake:
• The base (housing) moves with the shaking ground.
• The mass, due to inertia, remains relatively stationary.

Relative Movement:

• The difference in motion between the mass and the base is recorded by the stylus.
• This creates a seismogram with peaks and troughs corresponding to the seismic waves strength and frequency

Key Components

• Mass-Spring System: A heavy mass attached to a spring while the base moves during an earthquake.
• Dashpot: A damping device that controls the movement of the mass to prevent excessive oscillation Housing/Base: Firmly fixed to the ground so it moves with the seismic waves.
• Recording System (Drum & Stylus): A rotating drum with paper

EARTHQUAKE MAGNITUDE SCALE'

• Is a numerical measurement that indicates the size of an earthquake based on the amount of energy released at its source.

TWO DIFFERENT SCALES USED TO QUANTIFY

### Earthquake Richter Scale
    - Developed by Charles F. Richter in 1934
    - Measures the magnitude of earthquake , or the amount of energy released.
    - Uses a logarithmic scales, so each whole number increase represents a tenfold increase in ground motion.

Modified Mercalli Scale

     - American seismologists Harry O. Wood and Frank Neumann invented the Modified Mercalli in 1931.
    - Measures the intensity of how much the ground shakes at a specific location.
    - Intensity measurements are generally higher near the source of an earthquake.

What is Siesmic Waves

- Seismic waves are vibrations that travels throught the earth caused by Earthquakes volcanic, eruptions expolsions and more.

Body Waves

• Bodywaves are seismic waves that travel through the interiors rather than across its surface seismic waves travel through Earth intetior and are created by the sudden movement of amterials within earth,
• Two types Body Waves (P,S Waves)

P-WAVES (PRIMARY WAVES)-

  - AlSO KNown primary waves or  compressional waves.
### S-WAVES (SECONDARY WAVES) -
  - Also Known secondary waves or shear  waves.

Surface Wave

- Seismic waves  move alone.

Examples of Surface Wave

    ## Love Waves
    ## Rayleigh Waves

SAFETY MEASURES DURING AN EARTHQUAKE

Precaution before An Earthquake

• Secure heavy objects
• Store heavy items low
• Check electrical and gas lines
• Learn safe spots and have emergency kit

Action during An Earthquake

• Drop - Cover
• Hold On

Actions After Earthquake

• Stay Informed
• Be ready to evacuate
• Help Others
• Watch for Aftershocks

Earthquake Effects

Effects on People

     - Earthqukes cau cause severe injuries trama and loss of life and espically in areas with weak structeres

Effects on Buildings and Roads

      - STROng earth qukes can lean to the collase to buildings bridges and other iinfrastuctcauseing major damage to comunties

Effects on the Environment

-Earthqukes that ehy the ground behaes like a liidand and Tsnaimes and whch can greal impact natire people hood

MODULE 5: EARTHQUAKE MEASUREMENTS

• Two main ways to measure EARTHQUAKES:
  • Magnitude
  • Intensity

Intensity Scale

• Intensity Shaking Description

EXAMPLE OF THE EFFECT

• The earthquake struck Michoacán, Mexico, southwest of Mexico City in 1985 which was located 350 km from epicenter

MODUILE 6: DYNAMICS OF VIBRATION

- The imortance of vibration analys in the design and maintsnces of structires as machlnes
    1.) Historical Context of Sturues
    2.) Changes over Time
    3.)Need for Vibration Anglysis
    4.) Consenes of Ignoring Vibration
    5.) Design s mediction

The Causes and effects of Structural Vibration

Two factors That control the amplitde and fequen of vibration in a strocu

   - The Extation apled
   - The es onse of the stricyure to that paiicrler Excaton

###Module 7 Dynamics of Vibration

• TYPES OF MOTION THAT CAUSES VIBRATION:
• Harmonic Motion
• Periodic Motion
• Force Vibration
• Free Vibration
• Damped Vibration
• Random Vibration

Harmonic Motion refers to the motion an oscillating mass experiences when the restoring force is proportional to the displacement, but in opposite directions.

###TYPES OF HARMONIC MOTION

• Simple Harmonic Motion – Oscillates with constant restoring force
• Damped Harmonic Motion – Oscillation decreases due to resistance
• Forced Harmonic Motion - External force drives continuous vibration

###Simple Harmonic Motion

• In simple harmonic motion, the acceleration of the system, and therefore the net force, is proportional to the displacement and acts in the opposite direction of the displacement.