Earthquakes Shake, Rattle and Roll

Types of stress (notes are in yellow font with light blue background pg. 45 Tension- a type of stretching force Compression- forces that squeeze (compress) Shearing force – pushes rock layers in two different direction

- Forces in Earth’s Crust

- Forces in Earth’s Crust

- Forces in Earth’s Crust

- What type of stress would cause a normal fault?

- What type of stress would cause a reverse fault?

- What type of stress would cause a strike slip fault?

Do you see folds or faults?

Types of faults (page 46-47

Faults and Folds A break or crack along which rocks can move is a Fault A fold is a bend in rock layers without a break or crack.

- Forces in Earth’s Crust

- Earthquakes and Seismic Waves

Epicenter and Focus The Epicenter is the point on the Earth's surface that is directly above the Focus, or point where an earthquake originates.

P – wave or Primary Wave The primary waves have the highest velocity of all seismic waves and are the first to arrive at any seismic station and can pass through liquid layers of the Earth Sound, as a compressional wave is also a longitudinal wave

- Earthquakes and Seismic Waves

S-(Secondary Wave) The S-wave moves as a transverse wave, so motion is perpendicular to the direction of wave travel. It is S-shaped, like waves in a rope, move slower than p waves and cannot travel through liquids

S waves curve like an s. They are secondary and slow

L- waves L (Love) waves dissipate (weaken) slowly due to the huge amount of energy that they contain. They are the most destructive around the area of the focus or epicenter of an earthquake. They are what most people feel directly during an earthquake.

- Earthquakes and Seismic Waves

- Earthquakes and Seismic Waves

Richter scale Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released, and each increase of 0.2 corresponds to a doubling of the energy released. Charles Richter circa 1970

Potentially perceptible Description Magnitude Frequency per year Great 8.0+ 1 Major 7.0-7.9 18 Large (destructive) 6.0-6.9 120 Moderate (damaging) 5.0-5.9 1,000 Minor (damage slight) 4.0-4.0 6,000 Generally felt 3.0-3.9 49,000 Potentially perceptible 2.0-2.9 300,000 Imperceptible less than 2.0 600,000+

One of the worst ever The great Alaska earthquake of March 27, 1964, is the largest earthquake in the United States. It had an esitmated magnitude of 9.2. 115 people died, with most of the deaths due to the tsunami it generated. Shaking was felt for an estimated 7 minutes, and raised or lowered the ground surface as much as 2 meters (6.5 feet) in some areas and 17 meters (approx. 56 feet) in others. The length of the ruptured fault was between 500 and 1,000 kilometers (310.5 and 621 miles). The amount of energy released was equal to 12,000 Hiroshima-type blasts, or 240 million tons of TNT.

- Earthquakes and Seismic Waves

- Earthquakes and Seismic Waves

Video On seismic shadows

where: k is the modulus of incompressibility μ is the modulus of rigidity; and ρ the density of the material through which the wave is propagating

- Monitoring Earthquakes

- Monitoring Earthquakes

- Earthquake Safety

- Earthquake Safety

Base Isolated Building With u shaped lead dampners And rubber isolation pads (Video- 2:30 to 4:30)