Seismicity

Question 1

What percentage of earthquakes that occur each day aren’t associated with plate boundaries?

Answer 1

5%

Question 2

How many earthquakes each year are considered to be major hazards?

Answer 2

3 or 4

Question 3

What depth are shallow focus earthquakes?

Answer 3

0-70km

Question 4

What depth are intermediate focus earthquakes?

Answer 4

70-300km deep

Question 5

What depth were deep focus earthquake?

Answer 5

300-700km deep

Question 6

Where do seismic shock waves have their highest energy?

Answer 6

At the focus

Question 7

What is the place on the earths surface immediately above the focus?

Answer 7

Epicentre

Question 8

Which waves are recorded on a seismograph?

Answer 8

P and S waves

Question 9

Which plate margins are the strongest earthquakes related to?

Answer 9

Destructive plate margins

Question 10

Describe earthquake at constructive plate margins

Answer 10

They are often submarine and usually distant from people, so there’s relatively little hazard

Question 11

Describe conservative plate margins

Answer 11

The boundary is marked by a fault or series of faults

Question 12

Name an example of a conservative plate margin

Answer 12

San Andreas Fault in California

Question 13

Why is there earthquakes in central China? e.g. Sichuan

Answer 13

Due to weaknesses in the crust connected to the collision of India with the Eurasian plate over 50 million years ago

Question 14

What is the magnitude of an earthquake?

Answer 14

The amount of energy released by a seismic event

Question 15

What is the Richter scale?

Answer 15

This is a logarithmic scale with each representing a ten fold increase in strength and a 30 fold increase in energy released.

Question 16

What magnitude do earthquakes have to be to be destructive?

Answer 16

In excess of 6

Question 17

What is the Modified Mercalli Scale?

Answer 17

It is an alternative measurement of earthquakes. It measures the intensity of the event and its impact.

Question 18

How many points does the modified mercalli scale have?

Answer 18

A 12 point scale

Question 19

What are aftershocks and how long do they last after the main seismic event?

Answer 19

They are smaller earthquakes following the main event, they can last for months after the event.

Question 20

What are the factors that influence the consequences of the earthquake?

Answer 20

1. The magnitude and depth of the earthquake
2. Geological conditions
3. The distance from the epicentre
4. Population density, preparation and education
5. The design and strength of the buildings
6. The time of day
7. The impact of indirect hazards, such as fires, landslides and tsunamis

Question 21

What is soil liquefaction?

Answer 21

When soils with a high water content lose their mechanical strength and start to behave like a fluid.

Question 22

How much damage did soil liquefaction cause in the 1989 Loma Prieta earthquake?

Answer 22

US$100,000 million

Question 23

Landslides and avalanches

Answer 23

Slope failure as a result of ground shaking. This can result in further deaths and injuries as well as flooding from blocked rivers creating ‘quake lakes’

Question 24

What do the effects of earthquakes on people and their built environment depend upon?

Answer 24

Depends upon population density and distance from the epicentre.

Question 25

What are the long term effects of earthquakes?

Answer 25

1. Higher unemployment 2. Repair and reconstruction of buildings and infrastructure may take months or years 3. Longer term illness as well as reduced life expectancy caused by immediate suffering 4. Trauma and grief may take months or years from which to recover 5. Emergency pre-fabricated buildings may become permanent fixtures 6. Permanent disruption to natural drainage patterns 7. Problem in restoring trust in neighbours and civil authorities if there has been civil disorder e.g. As in Haiti

Question 26

What are tsunamis generated by?

Answer 26

They are generated by seismic activity caused by ocean floor earthquakes or submarine volcanoes

Question 27

What speeds can tsunamis travel up to?

Answer 27

700km/hour

Question 28

What factors will a tsunamis effects depend on?

Answer 28

1. The height of the waves and the distance they have travelled 2. The length of the event that caused the tsunami 3. The extent to which warnings were given 4. Coastal physical geography, both offshore and the coastal area 5. Coastal land use and population density

Question 29

How many people were killed by the tsunami caused by the 1883 Krakatoa eruption?

Answer 29

35,000 were killed by waves which were up to 40m high

Question 30

What percentage of tsunamis are generated in the Pacific basin?

Answer 30

90% of all tsunamis

Question 31

What percentage of all tsunamis are generated in the | Japan-Taiwan island arc?

Answer 31

25%

Question 32

What are the two devastating tsunamis which have occurred after the December 2004 tsunamis?

Answer 32

1. July 2006, South Java coast | 2. April 2007, Solomon Islands

Question 33

What magnitude earthquake caused the south Java coast tsunami and how many people were killed?

Answer 33

generated by a magnitude 7.7 earthquake. More than 600 people were killed

Question 34

How many people were killed in the Solomon Islands tsunami?

Answer 34

At least 15 people

Question 35

The Pacific Tsunami Warning System based in Hawaii warns people of tsunamis, what are its levels of warning?

Answer 35

1. Important 2. Major 3. Serious

Question 36

How do seismic records help predict earthquakes?

Answer 36

They can be studied to look for patterns. Seismic shockwaves are recorded on a seismometer.

Question 37

How do radon gas emissions help predict earthquakes?

Answer 37

Radon is an inert gas that's released from rocks such as granite at a faster rate when they're fractured by deformation

Question 38

How does measuring groundwater levels help predict earthquakes?

Answer 38

Deformation of the ground can cause water levels to rise (compression) or fall (tension) independently of atmospheric conditions

Question 39

How does remote sensing help predict earthquakes?

Answer 39

There's some evidence to suggest that electromagnetic disturbances in the atmosphere directly above areas about to have an earthquake can be detected

Question 40

What're the three main types of protection when protecting from earthquakes?

Answer 40

1. Making buildings earthquake resistant 2. Raising public awareness 3. Improving earthquake prediction

Question 41

What is special about the bottom storey of some Japanese buildings?

Answer 41

They are a 'soft storey' which is designed to collapse in the event of an earthquake

Question 42

In Tokyo what are citizens advised to keep in case of the event of an earthquake?

Answer 42

Supplies such as food, water, blankets and a first aid kit.

Question 43

What can be installed to reduce the fire risk after an earthquake in some countries?

Answer 43

A 'smart meter' which can be fed seismic data and can shut down gas supplies automatically in the event of an earthquake

Question 44

What percentage of the population of Kobe had earthquake insurance before the 1995 quake?

Answer 44

7%