GEOL 1 Lecture Notes - Lecture 4: Seismic Wave, Mercalli Intensity Scale, Seismic Moment
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Published on 19 Oct 2020
School
Department
Course
Professor
Jeff Koo
Geol 1
Physical Geology
Spring 2019
4 Units
Primary waves
- Compression waves
- Try to change volume so they can go through solids and liquids
- Travel 6 km/ sec through granite
- P waves are one type of body wave
- Compression expansion
Secondary waves
- Shear waves
- Try to change shape but no volume
- So they can’t go through liquid
- 3.5 k.m/sec through granite
- S waves are another type of body wave *sliding
- Where there is oil no s waves go through *that is how they explore where there is oil
*surface waves have a rolling sensation motion like a wave on a ocean
Epicenter pg.409
- Is the place above earthquakes – actually happens
- Hypocenter: the focus-the center of the earthquake, the point of initial breakage and
movement on a fault. Rupture begins at the focus and then spreads rapidly along the fault.
Locating an earthquake pg.411
-the instrument used to measure seismic waves is a seismometer
- When the P waves and s waves arrive at the seismograph
- How fast each type of wave makes
- Both types originated at the same place and the same time
Locating an earthquake
- The earthquake occurred
Earthquake magnitude pg. 414
- By intensity
- By measuring the amount of energy released by the quake
o Righter scale- based on the maximum seismic wave amplitude on a seismogram –
after doing that they can measure the magnitude by using a righter scale
- 3- seismic moment- by the strength of the rock, surface area of the rupture…
Energy release
- The energy released by earthquakes increases more than 30 times earthquakes equal the
energy released by 1 m6 quake!
Modified Mercalli intensity pg.414