Lecture 7 - Earthquakes

Question 1

What is an Earthquake?

Answer 1

Release of accumulated elastic strain causes rupture of a rock along a fault.

Question 2

Strain Definition

Answer 2

A measure of the amount of deformation that has been experienced by a volume of rock.

Question 3

Stress Definition

Answer 3

The force acting per unit area on any defined plane within the volume of rock.

Question 4

Epicentral distance definition

Answer 4

Distance from the epicentre to a seismic recording station, either in km or degrees

Question 5

Different earthquake focal depths

Answer 5

Shallow - 0-70km
Intermediate 70-300km
Deep - 300-700km

Question 6

Earthquake fatalities

Answer 6

10,000 deaths globally per year.

Question 7

Scientific issues surrounding earthquakes

Answer 7

1. Seismic hazard - Pop density, location and strength of buildings and infrastructure.
2. Earth Structure - Earthquake waves give primary information about Earth’s structure.
3. Tectonics - location, size and character give us information about tectonics actively going on.

Question 8

Secondary natural hazards from Earthquakes

Answer 8

• ground shaking
• ground failure/movement
• landslides
• avalanches

Question 9

Anthropogenic hazards

Answer 9

• damage to infrastructure
• floods from dam failures and leaks
• disruption of transport

Question 10

What does seismic hazard strongly depend on?

Answer 10

Composition and fluid content of the substrate.

Question 11

Tsunami Hazard

Answer 11

Generated by seafloor movement
Far-reaching effects
Many influences such as local shelf bathymetry and coastal morphology

Question 12

Submarine Landslides

Answer 12

Slope failure in terrestrial and submarine environments.
May produce a tsunami

Question 13

What is used to determine earthquake potential?

Answer 13

• Instrumented records
• Historic records
• Sedimentary records - of landslides, tsunamis,