Mountains Lecture 6- The Black Swan: why extreme events matter, and why they are hard to predict

Question 1

What is the definition of uniformitarianism?

Answer 1

The present is the key to the past

Question 2

What is the history of uniformitarianism?

Answer 2

Theory grew from James Hutton’s geological observations.
However, was widely disseminated and popularised by Charles Lyell in his Principles of Geology (1830-1833).

Question 3

What does uniformitarianism suggest?

Answer 3

Events we have experienced are representative of earths history.
We can take modern observations and knowledge surrounding them and infer something about past processes, conditions and events.

Question 4

Name three events where there is no recent or historical analog.

Answer 4

Formation of the moon
Supervolcanoes and plateau basalt eruptions
Impacts and mass extinctions

Question 5

What is neocatastrophism?

Answer 5

A view surrounding if large events with no modern analogue are important in Earth history

Question 6

What do we need to know about to understand the role of catastrophic events?

Answer 6

1. The distributions of events in terms of their size and frequency
2. Their effectiveness, or ability to cause some change to the system

Question 7

What can Earth events be described in terms of?

Answer 7

Magnitude and frequencies

Question 8

When were the two large-magnitude Sumatra earthquakes?

Answer 8

26 December 2004 - 9.3
28 March 2005- 8.7

Question 9

What was thr roung length of the Sumatra earthquake rupture?

Answer 9

Distance from Baltic Sea to Sicily

Question 10

What did the 2005 Sumatra earthquake cause?

Answer 10

> 2m of permanent rock uplift in places and fundamentally altered the coastline.

Question 11

How many earthquakes with a magnitude of 8 or higher occur annually?

Answer 11

3

Question 12

How many earthquakes of 7-7.9 magnitude occur annually?

Answer 12

16

Question 13

How many earthquakes of 6-6.9 magnitude occur annually?

Answer 13

140

Question 14

How many earthquakes of 5-5.9 magnitude occur annually?

Answer 14

2047

Question 15

How many earthquakes of 4-4.9 magnitude occur annually?

Answer 15

Around 13,000

Question 16

How many earthquakes of 3-3.9 magnitude occur annually?

Answer 16

Around 130,000

Question 17

How many earthquakes of 2-2.9 magnitude occur annually?

Answer 17

Around 1,300,000

Question 18

What institution tracks and complies the number of ‘locatable’ earthquakes?

Answer 18

US National Earthquake Information Centre

Question 19

Does the number of earthquakes vary much each year? Does the impact on human lives?

Answer 19

1. No
2. Yes

Question 20

How many deaths for Sumatra earthquake?

Answer 20

298101

Question 21

How many deaths for Haiti earthquake?

Answer 21

226050

Question 22

What was magnitude of 2010 Haiti earthquake?

Answer 22

7.0

Question 23

What is the only 8+ Mw earthquake to occur in 2019 and how many casualties?

Answer 23

Peru - 26th May
2 casualties

Question 24

Discuss the 2011 Great Tohoku earthquake.

Answer 24

9 Mw
Japan
20896 deaths
Tsunami caused more deaths than the earthquake
Events led to Fukushima nuclear accident

Question 25

Does a 'cherry picking of results' suggest evidence for earthquakes with high magnitude increasing?

Answer 25

Yes - clustering seen If magnitude threshold changes then large earthquake occurrence seems largely random.

Question 26

What are challenges of magnitude-frequency plots?

Answer 26

Number of small events are under-predicted as many are too hard to locate. Cannot distinguish the number of magnitude 6-8 events

Question 27

What is an alternative scale to a magnitude-frequency plot?

Answer 27

Using a logarithmic scale

Question 28

How can frequency-magnitude plots help work out number of earthquakes of each magnitude?

Answer 28

Using a y-axis log scale can suggest that as we increase earthquake magnitude the number of events decreases - following a straight line.

Question 29

What is the straight line equation?

Answer 29

y = n + mx

Question 30

What is the equation to predict number of earthquakes of each magnitude using a straight line?

Answer 30

logN = a - bM M= magnitude N= number of earthquakes a is intercept b is slope

Question 31

What is the relationship between frequency and magnitude called using a graph?

Answer 31

Gutenberg-Richter law (mid 20th century). Can be defined for global, region or local datasets and can tell you expected number of earthquakes of a given size.

Question 32

What is frequency of exceedance?

Answer 32

How often an event of at least that size is expected to occur

Question 33

What is PGA?

Answer 33

Peak ground acceleration. The maximum shaking in an earthquake, as a function of Earth's gravity

Question 34

What is predicting earthquake frequency-magnitude useful for?

Answer 34

Forcasting likelihood of future events and for understanding their effects.

Question 35

Why may different regions or different parts of the same fault have different frequency-magnitude relationships?

Answer 35

Straight lines have different slopes (b values). Therefore likelihood of specific magnitude events and relative numbers of big vs small events is therefore different.

Question 36

What does a small b-value mean?

Answer 36

Large average earthquake size and proportionally more large events

Question 37

What does a large b-value mean?

Answer 37

Smaller average earthquake size, and proportionally more small events

Question 38

What can b values be used to calculate?

Answer 38

Daily earthquake probabilities. Maps can show the likelihood of ground shaking with intensity. Probabilities are not accurate predictions

Question 39

Discuss the L'Aquilia earthquake

Answer 39

Italy 6th April 2009 6.3 Mw 309 deaths Low-magnitude tremors (seismic swarms) leading up No evacuation Manslaughter charges

Question 40

What is the difference between uniformitarianism and neocatastrophism?

Answer 40

Uniformitarianism suggests that events we have experienced are representative of Earth History. Neocatastrophism is where large events – where there is no recent or historical analog – are thought to have had a profound impact on the evolution of the Earth system

Question 41

What happened to Sumatra’s coast after the 2005 earthquakes?

Answer 41

Earthquakes caused >2m of permanent rock uplift in places – beach appeared to ‘rise’ out of the sea

Question 42

Briefly (and in simple terms) describe how earthquake magnitude and impact for Earth varies over time.

Answer 42

The total number of earthquakes each year doesn’t vary that much over time. The number of deaths however can vary considerably

Question 43

What is the Gutenberg-Richter law?

Answer 43

The relationship between the magnitude and total number of earthquakes in any given region and time interval

Question 44

In earthquake frequency-magnitude plots what does it tell you if the b value is a) small and b) large?

Answer 44

Small b-value: large average earthquake size, and proportionally more large events. Large b-value: smaller average earthquake size, and proportionally more small events.

Question 45

What can trigger landslides in mountain environments?

Answer 45

Rainfall and earthquakes

Question 46

Where is the asthenosphere located?

Answer 46

Upper mantle

Question 47

What is an example of a divergent plate boundary?

Answer 47

Mid Atlantic Ridge

Question 48

What is the process where the Earth's surface moves up relative to another section due to earthquakes and movement along faults?

Answer 48

Tectonic rock uplift

Question 49

In the earthquake cycle, what happens when the stress exceeds the local rock strength?

Answer 49

Earthquake

Question 50

What parameters do you need to know to calculate the seismic moment of your earthquake?

Answer 50

Average slip of earthquake and fault area erupted

Question 51

What is erosion?

Answer 51

The removal and transport of rock, soil or dissolved material

Question 52

What is sediment load?

Answer 52

The mass of sediment leaving a catchment per unit time

Question 53

What can the geochemical composition of sediment/sediment cores tell us about a mountain range?

Answer 53

Source area of sediment

Question 54

Until 40 Myr ago, through which river did most of E Tibey drain through?

Answer 54

Red

Question 55

What is 'diffusive sediment transport'?

Answer 55

Independent grain movement under gravity

Question 56

What characteristics might your mountain range have if it is composed of very sttrong rock?

Answer 56

High relief and steep hillslope gradients

Question 57

How does that degree of rock exposure typically change with distance downstream?

Answer 57

Decrease

Question 58

Frequency-magnitude plots are difficult to interpret as the raw data only is plotted. How might you transform the data to better show these relationships?

Answer 58

Transform frequency data to a logarithmic scale.