sci co2.1

• Earthquake

  refers to a weak to violent shaking of the ground due to sudden movement of rock material below the surface.
• Tectonic

  sudden movement along faults and plate boundaries
• Volcanic

  due to rising lava or magma beneath active volcanoes
• tectonic plate boundaries

  Earthquakes primarily originate from
• Hypocenter

  also known as focus

  it is the point inside the Earth where the earthquake originated
• Epicenter

  the point on the Earth’s surface directly above the focus
• PLATE TECTONICS

  Plates are large slabs of the Earth’s lithosphere that ride on a partially hot molten layer of the upper mantle or asthenosphere

  The plates tend to move in a continual slow motion, and cause interaction with its neighboring plates causing stress on margins
• The Elastic Rebound Theory

  explains that most earthquakes are produced by the rapid release of energy stored in rocks that had been subjected to great stress

  Upon exceeding the rock strength, it suddenly ruptures,causing vibrations of an earthquake
• Foreshock

  smaller scale earthquake that comes before a stronger earthquake
• Mainshock

  largest scale of earthquakes in a series
• Aftershock

  smaller-scale earthquake that comes after a larger earthquake 

  occurs as the ground tried to return to its original position after the earthquake
• SEISMOMETER

  instrument used to measure seismic waves which may be a pendulum or a mass mounted on a spring
• SEISMOGRAPH

  an instrument or recording device that produces a permanent record of Earth motion detected by a seismometer
• SEISMOGRAM

  is the recording of the ground shaking at the specific location of the instrument 
• TWO BASIC CONFIGURATIONS OF SEISMOMETERS

  VERTICAL-MOTION SEISMOMETER

  HORIZONTAL-MOTION SEISMOMETER
• VERTICAL-MOTION SEISMOMETER

  RECORDS UP-AND-DOWN GROUND MOTION
• HORIZONTAL-MOTION SEISMOMETER

  RECORDS BACK-AND-FORTH GROUND MOTION
• INTENSITY

  THE EFFECT OR CONSEQUENCE OF AN EARTHQUAKE’S GROUND SHAKING AT A LOCALITY ON THE EARTH’S SURFACE
• MAGNITUDE

  a number that characterizes the relative size of an earthquake.

  It is based on measurement of the maximum motion recorded by a seismograph
• SCALES USED TO QUANTIFY EARTHQUAKE MAGNITUDE:

  RICHTER MAGNITUDE OR LOCAL MAGNITUDE (ML) 

  SURFACE-WAVE MAGNITUDE (MS)

  BODY-WAVE MAGNITUDE (MB)

  MOMENT MAGNITUDE (MW)
• In 1902, an Italian scientist named Giuseppe Mercalli devised a scale for defining intensity by systematically assessing the damage that the earthquake caused
• Note that the specification of earthquake intensity depends on a subjective assessment of damage, and of the perception of shaking, not a direct measurement with an instrument
• RICHTER MAGNITUDE SCALE

  Developed by Charles Richter

  Based on the maximum amplitude of motion that would be recorded at a station about 100 km from the epicenter.

  The original Richter Scale works well only for shallow earthquakes that are close to the seismometer station – now called local magnitude (ML)
• Where I stands for the intensity of the earthquake and I0 represents a zero-level earthquake the same distance from the epicenter

  
• Ground Shaking

  is the disruptive up-down and sideways movement or motion experienced during an earthquake and is responsible for the collapse of structures
• Up and down 

  first felt by people near the epicenter; not felt by people far from epicenter
• Sideways

  felt after up and down by people near epicenter; first felt by people far from epicenter
• Ground shaking is considered both as a hazard created by earthquakes and a trigger for other hazards such as liquefaction and landslides

  It is usually recorded in terms of intensity
• GROUND RUPTURE

  It refers to the displacement on the ground due to movement of a fault

  Structures that are built across fault lines may experience collapse, whereas structures built adjacent to the fault may survive
• LIQUEFACTION

  the process where the unconsolidated sediments lose grain-to-grain contact during ground shaking, thus act almost as a liquid

  In some water-saturated sediments, the water may be expelled from the spaces between grains
• TSUNAMI

  are giant ocean waves that rapidly travel across oceans

  These sea waves are formed due to the disturbance of the ocean floor by an earthquake landslides
• An Earthquake-induced landslide

  refers to failures in steep or hilly slopes triggered by ground shaking

  It commonly occurs in mountainous regions
• Earthquake Hazards include:

  Ground shaking

  Ground rupture

  Liquefaction

  Tsunami

  Earthquake-induced landslide
• STRUCTURAL EARTHQUAKE RESISTANT DESIGN

  written in the National Structural Code of the Philippines (2010)
• Seismic Damper 

  is a device that dissipates kinetic energy
• When seismic waves start to penetrate the base of a building structure, seismic dampers can decrease their damaging effect and improve the building’s seismic performance
• ACTIVE CONTROL (MECHANICAL ACTUATORS) & ENERGY ABSORBER

  It utilizes the feedback from sensors measuring the response of a structure to control the behavior of structural elements through mechanical actuators
• BRACED FRAMES

  structural systems designed to resist wind and earthquake forces
• MITIGATION MEASURES GROUND RUPTURE

  APPROPRIATE ENGINEERING INTERVENTIONS ARE AS FOLLOWS:

  NO KNOWN SOLUTION

  NO STRUCTURE SHOULD BE BUILT EXACTLY ON TOP

  BUFFER ZONE IS 5 METERS ON BOTH SIDES OF THE FAULT
• MITIGATION MEASURES GROUND SHAKING

  Appropriate engineering interventions are as follows:

  Structural Earthquake Resistant Design

  Base Isolation (Dampers)

  Active Control (Mechanical Actuators)

  Energy Absorber

  Braced Frames