PRESENTATION ON EARTHQUAKE SILVER OAK COLLEGE OF ENGINEERING & TECHNOLOGY Prepared by :Adviser : Nirav R Dabhi 11CLD09Dulari Mehta Simal B Gandhi 11CLD10Khushbu Bhojak Parth J Bhavsar 11CLD12 Ketul P Mandavia 11CLD14
• An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earths crust that creates seismic waves.• An earthquake is caused by a sudden rupture (break) of the earth• The most largest earthquake of 9.5 magnitude earthquake in Chile in 1960.• The most recent earthquake of 9.0 magnitude earthquake in Japan in 2011 (as of March 2011), and it was the largest Japanese earthquake since records began.• It struck at 7.58am on December 26, 41 miles off the coast of north-west Sumatra where 200,000 are now thought to have been killed in just 15 minutes.
• Passing the Elastic Limit Causes Faulting• Applied stresses can cause rocks to bend and stretch• Eventually rocks will break away from one another• Area in which the rocks break and move is called a fault• Vibrations produced is called an earthquake• Earth’s crust movement causes the stresses applied
• Response of material to the arrival of energy fronts released by rupture• Two types: • Body waves • P and S • Surface waves • R and L
• Body waves • P or primary waves • Fastest waves • Travel through solids, liquids, or gases • Compression wave, material movement is in the same direction as wave movement • Energy waves that cause rocks to move back and force in the • same direction • • Compression and stretching forces are created
• S or secondary waves • Slower than P waves • Travel through solids only • Shear waves - move material perpendicular to wave movement • Energy waves that cause rocks to move at right angles to the wave
• Surface Waves • Travel just below or along the ground’s surface • Slower than body waves; rolling and side-to-side movement • Especially damaging to buildings • Energy waves that move rocks in an elliptical motion
Seismic waves do not travel through earth’s surface at the same speed Primary waves are the fastest Surface waves are the slowest• Earthquake focus • Focus – the point in Earth’s interior where the energy waves are produced• Seismic waves • Seismic wave - the energy waves that move outward from the earthquake focus and make the ground quake• Epicenter • The point on Earth’s surface directly above the earthquake focus
• Normal Fault• Earth’s plates move apart• Movement of the plates causes tension• Rocks above the fault surface move downward in relation to the rocks below the fault surface
• Reverse Faults• Compression forces are applied because Earth’s plates are coming together• Causes rocks to bend and break• Rocks above the fault surface are forced up and over the rocks below the fault surface
• Strike-slip Fault• Earth’s plates move sideways to one another• Creates a shear force• Rocks on either side of the fault surface are moving past each other without much upward or downward movement
• Seismograph stations • Record the information from the earthquake by recording the different types of waves as they reach the station
• Epicenter Location • If information is received from the earthquake at three stations, then the epicenter can be located • A circle is drawn around each station on a map • The radius is equal to the distance from the station to the epicenter • The point in which all three circles intersect is the earthquake epicenter
• Seismology • Seismologists - People who study earthquakes and seismic waves • Use instruments called seismographs • Record seismic waves • A drum with a sheet of paper vibrates and a stationary pen marks the vibrations on the paper • The height of the lines are used to measure the energy released from the earthquake called the magnitude
• Earthquake Magnitude • Usually determines the strength of the break • Doesn’t determine the duration or the size • For each increase of 1 is 10 times stronger • An earthquake of 4 is 10 times stronger than an earthquake of 3• Caused by the movement of the ocean floor • Causes a disruption in the water • Some are so wide that a large ship can travel over the wave without knowing • Recent earthquake in the Indian Ocean created a tsunamis that was 100 feet high and moving at 500 mph
• Shaking and Ground rupture • Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures.
• The severity of the local effects depends on the complexcombination of the earthquake magnitude, the distancefrom the epicenter, and the local geological andgeomorphologic conditions, which may amplify or reducewave propagation.• The ground-shaking is measured by ground acceleration.
• Landslides and avalanches• Earthquakes, along withsevere storms, volcanicactivity, coastal waveattack, and wildfires, canproduce slope instabilityleading to landslides, amajor geological hazard.• Landslide danger maypersist while emergencypersonnel are attemptingrescue.
• Fires • Earthquakes can cause fires by damaging electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. • For example, more deaths in the 1906 San Francisco earthquake were caused by fire than by the earthquake itself.
• Soil liquefaction• Soil liquefaction occurswhen, because of theshaking, water-saturatedgranular material (such assand) temporarily loses itsstrength and transformsfrom a solid to a liquid.• Soil liquefaction maycause rigid structures, likebuildings and bridges, to tiltor sink into the liquefieddeposits.
• This can be a devastating effect of earthquakes. Forexample, in the 1964 Alaska earthquake, soil liquefactioncaused many buildings to sink into the ground, eventuallycollapsing upon themselves.
• Tsunami • Tsunamis are long- wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water. • In the open ocean the distance between wave crests can surpass 100 kilometers (62 mi), and the wave periods can vary from five minutes to one hour.
• Such tsunamis travel 600-800 kilometers per hour (373–497miles per hour), depending on water depth.• Large waves produced by an earthquake or a submarinelandslide can overrun nearby coastal areas in a matter ofminutes.• Tsunamis can also travel thousands of kilometers across openocean and wreak destruction on far shores hours after theearthquake that generated them.
• Floods • A flood is an overflow of any amount of water that reaches land. • Floods occur usually when the volume of water within a body of water, such as a river or lake, exceeds the total capacity of the formation, and as a result some of the water flows or sits outside of the normal perimeter of the body.
• However, floods may be secondary effects ofearthquakes, if dams are damaged.• Earthquakes may cause landslips to dam rivers, whichcollapse and cause floods.
• Human impacts • An earthquake may cause injury and loss of life, road and bridge damage, general property damage (which may or may not be covered by earthquake insurance), and collapse or destabilization (potentially leading to future collapse) of buildings. • The aftermath may bring disease, lack of basic necessities, and higher insurance premiums.
• Seismic safe structures • Structures that are resistant to the vibrations of Earth’s crust • Structures are made with moorings • Made of steel and are filled with alternating layers of rubber and steel • These structures absorb the energy produced from the earthquake
Damage in Oakland, CA, 1989• Building collapse• Fire• Tsunami• Ground failure