EOSC 114 Lecture Notes - Lecture 8: Return Period, Dune, Hypocenter
12 Sep 2016
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Document Summary
The longer the shaking, the worse it is. More shallow than body waves, therefore more damaging to buildings. Period length of time between successive waves. Amplitude displacement of the wave from an undisturbed position. Frequency - number of waves passing a certain point in 1 second. Higher frequency waves attenuate/die off faster than lower frequency waves. External forces imposed at this frequency can cause resonance. Factors that influence our perception of earthquake intensity: factors related to the size of the earthquake, magnitude. Shorter duration of shaking: distance from epicenter. Short = perceived as less intense, less damage. Long = perceived as more intense, more damage. Why are contour lines not perfect circles around the epicentre: local factors, ground properties. Filters the frequencies of the earthquake affects how long the shaking continues influences stability of the structure (foundations) soft ground more problematic. Buildings on bedrock or compacted sediments are safer. Wet, loose sediment and artificial fill have longer and harder shaking.
