Engineering Geology and Geohazards Lecture 10: Introduction to seismology and seismic waves

Question 1

What causes earthquakes

Answer 1

Plate tectonic movements, which are
themselves the result of the Earth transporting
heat outwards from its centre by convection.

Question 2

Define an earthquake

Answer 2

Sudden release of accumulated elastic
strain energy (producing seismic waves)
in a specific area of the Earth’s
lithosphere, normally through
reactivation of a fault.

Question 3

Describe Stress

Answer 3

Stress is directed force, measured in pascals
(Pa). 1 pascal = 1 N/m2 (Newton =
gravitational force of 102 grams, an average
apple)

Often measured in megapascals (MPa), Pa
x 106

Question 4

Describe Strain

Answer 4

Strain is the result of stress, ie., deformation.

• Three types: elastic, plastic, brittle