Earthquake hazards and impacts

Question 1

How many EQ’s are there globally every year and how many do they kill?

Answer 1

100,000 EQ’s and Kill 10’000

Question 2

What are the different EQ waves?

Answer 2

P waves, S waves and L waves

Question 3

What wave causes the greatest damage?

Answer 3

Love waves

Question 4

What is used to measure seismic waves?

Answer 4

A Seismometer recorded on a seismograph

Question 5

What is the order with which the waves arrive

Answer 5

1. P waves
2. S waves
3. L waves

Question 6

What two characteristics do Seismologists measure EQ’s

Answer 6

Magnitude (energy) and Intensity (Impacts)

Question 7

What is EQ magnitude measured in?

Answer 7

The Moment Magnitude Scale (MMS)

Question 8

What does the MMS scale measure?

Answer 8

Energy released at the epicentre at the seismic moment

Question 9

Describe the scale of the MMS

Answer 9

Starts at 1 and is infinite (the largest was in Chile in 1960 at 9.5). It is logarithmic e.g. MMS 9 = 32 x MMS 8

Question 10

Somerset 2019

Answer 10

MMS 3.2 - Resident reported house rattled

Question 11

Chile 1960

Answer 11

MMS 9.5 - Largest EQ ever recorded - 2 billion times more energy than Somerset 2019

Question 12

What does EQ intensity refer to?

Answer 12

Refers to the impacts on Landscape, Infrastructure and people

Question 13

What does the Mercalli Intensity Scale (MIS) use?

Answer 13

Uses witness observation to rate the EQ

Question 14

What is the range of the (MIS)?

Answer 14

Ranges from I (hardly noticed) to XII (catastrophic)

Question 15

What level was the Chile 1960 EQ on the MIS

Answer 15

XII - Total destruction

Question 16

What are Primary EQ hazards?

Answer 16

Hazards directly caused by the EQ and occur during the EQ

Question 17

What are Secondary EQ hazards?

Answer 17

Hazards indirectly causes by the EQ (knock on effects of the primary hazards) and can occur during or after the EQ

Question 18

The Loma Prieta 1989 EQ (Effect of geology)

Answer 18

MMS 6.9 EQ - The city’s Marina district was built on man-made landfill which resulted in Liquefaction causing buildings to collapse

Question 19

What are Aftershocks?

Answer 19

Smaller EQ’s triggered by the mainshock which can take place seconds or years after the original EQ due to the plates “settling down again” and can be more deadly than the mainshock

Question 20

What happened in Christchurch in 2011

Answer 20

An aftershock where the epicentre was closer to the city and the infrastructure was already weakened

Question 21

Why would EQ prediction be good?

Answer 21

It could save lives through evacuation however it is not fully possible yet

Question 22

What EQ prediction is possible now?

Answer 22

The arrival of deadly L waves can be predicted seconds / minutes before they hit when the P waves arrive, this can give much needed time for evacuation etc

Question 23

What is EQ forecasting?

Answer 23

Determines the probability for a place to experience an EQ

Question 24

How is EQ forecasting possible?

Answer 24

It is possible by looking at the tectonic setting and past EQ’s

Question 25

Why do 95% of EQ’s occur at plate boundaries?

Answer 25

Friction occurs and stress builds as plates try to move, eventually the stress overcomes the friction resulting in sudden plate movement as energy is released as seismic waves

Question 26

What are Intra-plate EQ’s?

Answer 26

They occur within plates, some occur at hot spots

Question 27

What is a hot spot?

Answer 27

Where a mantle plume underlies a plate and melts through the lithosphere and seismic energy is released

Question 28

What is an example of a hot spot?

Answer 28

Hawaii is a hot spot in the middle of the pacific plate 3000km from the nearest plate boundary

Question 29

What can also cause Intra-plate EQ’s other than hotspots?

Answer 29

other EQ’s can occur at ancient faults where there are fractures in the lithosphere which are reactivated by stress, however this is poorly understood

Question 30

What is an example of an ancient fault?

Answer 30

New Madrid in Missouri 1811-12