Earthquake and tsunami
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1) An earthquake is intense ground shaking caused by a sudden release of energy, often due to movement along faults within the Earth. 2) Earthquake magnitude is measured by the Richter Scale, where each whole number increase means the amplitude of shaking is 10 times greater. Magnitude 2.5 or less quakes are usually not felt, while anything above 8 can totally destroy communities near the epicenter. 3) Intensity refers to the amount of damage at a location and is measured by scales like Modified Mercalli, depending on factors like distance from the quake and duration of shaking.
Earthquake and tsunami
- 1. EARTHQUAKES
- 2. WHAT IS AN EARTHQUAKE? • intense ground shaking caused by sudden release of energy • can be generated by bomb blasts, volcanic eruptions and sudden slippage along faults • a geologic hazard for those living in earthquake- prone areas • also provided valuable information about the Earth’s interior
- 6. Body and Surface waves
- 8. EARTHQUAKE MAGNITUDE SCALE Magnitude Earthquake Effects Estimated Number Each Year 2.5 or less Usually not felt, but can be 900,000 recorded by seismograph. 2.5 to 5.4 Often felt, but only causes 30,000 minor damage 5.5 to 6.0 Slight damage to buildings 500 and other structures 6.1 to 6.9 May cause a lot of damage 100 in very populated areas. 7.0 to 7.9 Major earthquake. Serious 20 damage. 8.0 or greater Great earthquake. Can One every 5 to 10 totally destroy communities years near the epicenter.
- 10. for each whole number you go up on the Richter scale, the amplitude of the ground motion recorded by a seismograph goes up ten times. Using this scale, a magnitude 5 earthquake would result in ten times the level of ground shaking as a magnitude 4 earthquake (and 32 times as much energy would be released). To give you an idea how these numbers can add up, think of it in terms of the energy released by explosives: a magnitude 1 seismic wave releases as much energy as blowing up 6 ounces of TNT. A magnitude 8 earthquake releases as much energy as detonating 6 million tons of TNT. TNT
- 12. DESCRIBING THE STRENGTH OF AN EARTHQUAKE Intensity is the degree of ground shaking at a given locale based on the amount of damage Depends on distance to earthquake & strength of earthquake Modified Mercalli Intensity Scale Philippine Earthquake Intensity Scale Magnitude is calculated from seismic records and estimates the amount of energy released at the source Depends on size of fault that breaks Richter Scale
- 13. MAGNITUDE OF AN EARTHQUAKE
- 14. INTENSITY OF AN EARTHQUAKE Philippine Earthquake Intensity Scale – I to X (PHIVOLCS)
- 16. STRUCTURAL DAMAGE DUE TO EARTHQUAKE VIBRATIONS DEPENDS ON: Wave amplitudes Duration of vibrations Nature of material upon which the structure rests Design of structure
- 17. Earthquake Destruction important factors: Nature of material upon which structure rests A building on bedrock experiences less movement compared to a structure built on loosely consolidated sediments (tend to amplify shaking)
- 19. Earthquake Destruction important factors: Intensity & duration of shaking Mexico City, 1985
- 20. Earthquake Destruction important factors: Building design :
- 21. DESTRUCTIVE EFFECTS OF EARTHQUAKES
- 22. SECONDARY EFFECTS OF EARTHQUAKES tsunamis landslides ground subsidence Fire Liquefaction
- 23. SECONDARY EFFECTS OF EARTHQUAKES: TSUNAMIS
- 24. SECONDARY EFFECTS OF EARTHQUAKES: LANDSLIDES
- 25. SECONDARY EFFECTS OF EARTHQUAKES: GROUND SUBSIDENCE
- 26. SECONDARY EFFECTS OF EARTHQUAKES: FIRES
- 27. SECONDARY EFFECTS OF EARTHQUAKES: LIQUEFACTION
- 28. PHILIPPINE EARTHQUAKE GENERATORS Oblique convergence of two subducting oceanic plates Collision zones Active faults
- 29. RECENT EARTHQUAKE 21.17 km BNPP occurred at 6:55 (Jan 12, 2009) with Magnitude 5 -USGS
- 30. RECENT DESTRUCTIVE EARTHQUAKES July 16, 1990, Luzon (7.7) Nov. 15, 1994, Mindoro (7.8) Mar. 6, 2002, Sultan Kudarat (6.8) Feb. 15, 2003, Masbate (6.2)
- 32. Recurrence interval of Marikina fault – 200 years We have our own stress system so we have different ‘waiting time’ – Rimando , R.
- 34. EARTHQUAKE PREDICTION: SHORT TERM • Monitor to look for patterns of recurrence • Strange animal behavior • Increase in seismic tremors (mini-quakes) • Seismic gaps • Gas emissions • Electromagnetic signals
- 35. EARTHQUAKE PREDICTION: EARTHQUAKE CYCLES
- 36. EARTHQUAKE PREDICTION: SEISMIC GAPS Seismicity map (1608 – 2004)
- 37. drill a deep hole in order to install instruments directly within the San Andreas Fault Zone electronic laser, ground movement monitoring system in California to study the San Andreas Fault seismograph seismic sensor