Earthquakes

Question 1

What causes earthquakes?

Answer 1

• Associated with the breakage and displacement of rock, often along faults
• Kinetic energy is released as seismic waves
• Seismic waves radiate through the Earth’s interior resulting in “shaking” at the surface

Question 2

How do earthquake location relate to plate boundaries?

Answer 2

Earthquakes are associated with plate boundaries

Question 3

Several Types of Earthquake Hazards

Answer 3

• Ground shaking produces sediment liquefaction (instability of the ground), mass wasting (landslides), and damage to buildings and other structures
• Fires following earthquakes can be catastrophic and fire-fighting capabilities may be compromised
• Often water lines and emergency equipment are damaged and utility and communications systems are disrupted
• A tsunami may be generated

Question 4

Explain how an Earthquake could lead to flooding

Answer 4

• Divert rivers
• Mass wasting into water
• Liquefaction

Question 5

The Elastic Rebound Theory (brittle deformation)

Answer 5

• Explains the origin of earthquakes
• Energy is stored in the form of elastically deformed rock. When the strain exceeds the strength of the rock it breaks and the energy is released

Question 6

Strain Release

Answer 6

Eventually the rock is no longer able to accommodate the buildup of strain and it ruptures, either along a pre-existing fault or at a new location

Question 7

Focus

Answer 7

where the rocks actually break, where energy is released from, can be at surface or 700km depth

Question 8

Epicenter

Answer 8

point at Earth’s surface directly above the focus, focus and epicenter may be at the same place but not common

Question 9

Clusters

Answer 9

Earthquakes tend to occur in clusters, in both time and space

Question 10

Intraplate Earthquakes

Answer 10

Most seismicity occurs at plate boundaries, but intraplate earthquakes are common

Question 11

Divergent, Convergent, and Transform Margins

Answer 11

• Are sites of frequent earthquake activity
• Poorly understood
• Most have shallow foci
• Tend to occur in soft, weak areas of plate interiors, caused by stresses transmitted from plate boundaries
• Reactivation of old rift zones or faults
• Hot spots

Question 12

Divergent Seismicity

Answer 12

Earthquakes occur in shallow crust b/c that’s all there is

Question 13

Convergent Seismicity

Answer 13

Zone of seismicity along plane of subduction zone is called Wadati-Benioff Zone

Question 14

Earthquakes Produce Four Types of Seismic Waves

Answer 14

Two types of Body Waves (within crust) and two types of Surface Waves (surface duh)

Question 15

Types of Body Waves

Answer 15

P-wave: fastest, solid/liquid, push/pull (compression/extension) motion
S-wave: 2nd fastest, solid only, side to side

Question 16

Types of Surface Waves

Answer 16

Rayleigh wave: 3rd fastest, surface, up/down forward/back motion
Love wave: slowest, surface, side to side motion

Question 17

Liquids do not resist changes in shape

Answer 17

Rather, they absorb S waves instead of transmitting them

Question 18

Speeds of these waves allow us to

Answer 18

locate Earthquakes

Question 19

Further away from the foci, the larger the

Answer 19

gap between P and S waves, and vice vera for closer

Question 20

Seismometers

Answer 20

Instruments that measure and help locate earthquakes

Question 21

Could an Earthquake be located with only 2 seismic stations?

Answer 21

No, need at least three to triangulate location of the earthquake

Question 22

Earthquake Magnitude

Answer 22

Expressed as whole number and a decimal fraction = Richter scale

Question 23

Modified Mercalli (MM) Intensity Scale

Answer 23

• Intensity expressed using MM Intensity Scale

- Scale is how much of humanity’s stuff got fucked up

Question 24

Difference Between Intensity and Magnitude?

Answer 24

Intensity is qualifiable, also depends on how prepared certain areas are, and magnitude is quantifiable
There is also no focus on assessing the damage since everyone is focused on saving lives after the earthquake.

Question 25

Seismology

Answer 25

• Study of seismic waves in order to improve our understanding of Earth’s interior
• Wave infraction is used to identify a discontinuity

Question 26

Seismic Data confirms:

Answer 26

the existence of discontinuities in Earth’s interior

Question 27

Mohorovicic Discontinuity

Answer 27

• the boundary between the Earth’s crust and the mantle
• ~8km beneath oceanic basins
• ~20-70km beneath continents

Question 28

Seismic Tomography

Answer 28

Uses seismic data from hundreds of seismic stations and hundreds of different earthquakes to provide a 3-D seismic velocity image of Earth’s interior