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# Earthquakes

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• Good afternoon everyone, it’s a pleasure to welcome you today. Let me just start by introducing myself. For those of you who don’t now me, my name is Laszlo Bertalan and I am a first year PhD-student at Department of Physical Geography and Geoinformatics. The subject of my presentation is the background of a horrible catastrophy at nowadays, the earthquakes. It will take about 10minutes to cover these issues.
• Before describeing the details, let me tell you a short definition of earthquakes according to an article I read recently on the internet. The question is what is the geological background of this?
• Let me explain that figure: Geologists determined the structure of the Earth, and later they observed a t the Mohorovicic discontinuity that shock waves begin to travel faster indicating a change of structure (the junction of the earth’s crust and mantle) . .
• Earthquakes are vibrations of the earth caused by the sudden movement of rocks that have been straind under pressure and according to this i f this pressure sudden release then creates seismic waves. Earthquakes occur along faults, which are fractures in the lithosphere, where regions of rock moves past each other.
• If we highlight the differences between these two waves: the P-waves are the primer/longitudinal waves, S-waves are the secunder/transversal waves.
• There are two other types at the surface too which are the slowest waves, but the most damaging: the love waves has horizontal motion the rayleigh waves has rolling/elliptical motion.
• After the waves let me quickly explain the basic definitions of earthquakes. The focus is the point on the fault where rupture occurs and the location from which seismic waves are released. The epicentre is the point on the earth’s surface directly above the focus. When the fault ruptures, waves of energy called seismic waves spread out in all directions as I described earlier. Aftershocks are earthquakes that follow the largest shock of an earthquake sequence. Aftershock can continue over a period of weeks, months or years.
• The majority of earthquakes are caused by active plates, so the e arthquake zone s overlap with plate bound a ries .
• Seismographs are instruments that detect and record ground shaking by earthquake waves.
• Scientists use two different scales for measuring earthquakes, let me pount out the differences between the Mercalli and the Richter scales. Mercalli scale: this scale is based on experience. It consist of 12 grade Richter scale: the intensity of the earthquake is determined by logarithmic scale.
• Before the end of my presentation I want to show some of the effects caused by earthquakes all over the world.
• It is the main effect created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures.  Haiti, 2010.
• Earthquakes, along with severe storms, volcanic activity, coastal wave attack, and wildfires, can produce slope instability leading to landslides, a major geological hazard
• Earthquakes can cause fires by damaging electrical power or gas lines.
• Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water. The main conclusion is that an earthquake may cause injury and loss of life, road and bridge damage, general property damage and destabilization of buildings. Well, this brings me to the end of my presentation.
• ### Earthquakes

1. 1. Earthquakes Laszlo Bertalan PhD-student
2. 2. What is an earthquake?► It is a sudden, rapid shaking of the Earth caused by the breaking and shifting of rock beneath the Earth’s surface and it creates seismic waves1Source:1 http://autocww2.colorado.edu/~toldy3/E64ContentFiles/EarthSciences/Earthquake.html
3. 3. Mohorovičić discontinuity speed-changes of shock waves
4. 4. Geological explanation ► Vibration ► Stress ► Waves ► Faults
5. 5. Types of Seismic Waves1 Seismic waves spread inside the Earth
6. 6. Types of Seismic Waves2 Seismic waves spread at the Earth surface
7. 7. Earthquake Terminology Aftershocks
8. 8. Location of earthquakes
9. 9. Observation of earthquakesSeismographs
10. 10. Earthquake Measurement Experience vs. Intensity
11. 11. Effects of earthquakes► Shaking and ground rupture► Landslides and avalanches► Fires► Tsunami► Floods► Human impacts
12. 12. Shaking and ground rupture
13. 13. Landslides
14. 14. Fires
15. 15. Tsunami & Floods
16. 16. Thank you for your kind attention!