1.12

Question 1

Himalaya facts

Answer 1

• Tethys Ocean between India and Asia closed 50 million years ago due to subduction
• fold mountains thrust upwards with continental collision they continue to be uplifted at the rate of 2cm/yr

Question 2

primary (P-waves)

Answer 2

• have a short wave length
• travel fast through solid and liquid eg the core
• waves push and pull in the direction of travel to create compressional and extensional zones
• least effective when distorted
• arrive first @ epicentre (can be monitored)

Question 3

Secondary (S-waves)

Answer 3

• slower than p-waves and only move through solid rock

- longer wavelength and movement is at right angles to direction of travel (vertical)

Question 4

Love (L-waves)

Answer 4

• slowest most destructive wave
• can only move at surface
• largest amplitude and can shake the ground horizontally as the waves travel forward

Question 5

Rayleigh (R-waves)

Answer 5

• only travels through the surface of the crust in a rolling motion (ground is moved up and down and side to side)
• responsible for most of the shaking felt by people

Question 6

suture

Answer 6

division line between two plates, deepest point this happens at is the root (tension highest here)

Question 7

primary effects of an EQ (direct)

Answer 7

• ground shaking (causes infrastructure to collapse)

- crustal fracturing (energy released)

Question 8

secondary effects of an EQ (indirect)

Answer 8

• landslides (EQ loosens and shakes rock slopes which increases stresses)
• liquefaction ( surface loses strength in violent shaking becoming more liquid than solid so loses its ability to support building foundations and acts as a fluid)

Question 9

how can EQ be predicted?

Answer 9

• v difficult to accurately predict foreshocks
• animal behaviour often acts as an indicator as they are more sensitive to Earth tremors
• P-waves can be useful to trigger early warning responses ie turn off gas and water mains and aid immediate response (if epicentre is far away)