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323: Geological Hazards > Seismology Related Reading > Flashcards

Seismology Related Reading Flashcards

Questions based on reading around Seismology - Name reference too. Lay (2011) Moodle -> Great Earthquake Ruptures in the Age of Seismo-Geodesy. Liquefaction, great earthquake hazards, landslides caused by EQs

1
Q

Between 2004-2011, how many great earthquakes (Mw >8) have occurred?

A

7 (Lay, 2011)

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2
Q

What is the rate of great earthquakes between 2004-2011 and the rate of great earthquakes over the last century?

A

1.9/yr vs 0.7/yr (Lay, 2011)

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3
Q

When was the last period of great earthquake activity?

A

1950’s to 1960’s (Lay, 2011)

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4
Q

Name the three greatest earthquakes which occurred in the last period of great earthquake activity

A

Kamchatka (1952, Mw: 9.0), Chile (1960, Mw: 9.5), Alaska (1964, Mw: 9.2)

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5
Q

What did all the recent great earthquakes have in common?

A

Each had some surprise, and acted in a way which was by no means predicted

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6
Q

Which authors observed sand boils in the form of sand volcanoes in the 2005 Kashmir Earthquake?

A

Sahoo et al, 2007

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7
Q

What are the three conventional liquefaction phenomenon, reviewed by (Authors)?

A

Sand boiling, ground cracking, lateral spread (Huang and Yu, 2013)

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8
Q

According to (Authors) what happens to the pore water pressure of saturated sand during an earthquake?

A

Increases rapidly (Huang and Yu, 2013)

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9
Q

According to (Authors) what happens to stress in saturated sand during an earthquake?

A

Reduces to zero (Huang and Yu, 2013)

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10
Q

What are the four most favorable conditions for liquefaction occurrence according to (Authors)?

A

Loosely packed, coarse silt to fine sand, saturated with ground water, shallow depths (Huang and Yu, 2013)

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11
Q

What are the two different mechanisms for sand boiling according to (Authors)?

A

Flat-cone sand volcanoes and eruption through pre-existing cracks (Huang and Yu, 2013)

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12
Q

What is sand boiling (Authors)?

A

Eruption of sand and water to surface (Huang and Yu, 2013)

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13
Q

Give an example where sand boiling occurred through pre-existing cracks (Authors in Authors)

A

2011 Yingjiang earthquake (Yao et al, 2011 in Huang and Yu, 2013)

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14
Q

Why do ground cracks (as a form of liquefaction) occur during earthquakes according to (Authors)?

A

Uneven distribution of material in soil layer (Huang and Yu, 2013)

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15
Q

Name an example where ground cracks have formed (as a form of liquefaction) during an earthquake (Authors in Authors) and their approximate widths

A

2008 Greece EQ, 2-8 cm (Margaris et al, 2010 in Huang and Yu, 2013)

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16
Q

What is lateral spread according to (Authors)?

A

Permanent horizontal liquefaction induced ground displacement (Huang and Yu, 2013)

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17
Q

Where does lateral spread most commonly occur, according to (Authors)?

A

Parallel to course of rivers (Huang and Yu, 2013)

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18
Q

Give and example of lateral spread during an earthquake (Authors in Authors)

A

2008 Greece EQ, incriments increased towards the sea with a maximum spread of 60 cm (Margaris et al, 2010 in Huang and Yu, 2013)

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19
Q

Name the 5 types of new liquefaction phenomena which occurred during 21st century EQ’s according to (Authors)

A

Liquefaction in areas of moderate seismic intensity, Liquefaction of gravelly soils, Liquefaction of deep-level sandy soils, Re-liquefaction in aftershocks, Liquid behavior of unsaturated sandy soils (Huang and Yu, 2013)

20
Q

What is the normal assumption for earthquake magnitude and epicentral distance in relation to magnitude (Authors in Authors)?

A

Larger magnitude and closer to epicenter is generally were liquefaction occurs (Huang and Yu, 2013)

21
Q

Give an example of where liquefaction occurred at a smaller magnitude than expected (note intensity scales) (Authors in Authors)

A

2008 Wenchuan Earthquake, VI on modified mercalli, where VI or less are noted as free from liquefaction. (Chen et al, 2009 in Huang and Yu, 2013)

22
Q

Give an example of where liquefaction occurred at a distance further from the epicenter than expected (Authors in Authors)

A

2011 Tohoku Earthquake – Liquefaction occurred 350-400km away in Tokyo bay (Bhattacharya et al, 2011 in Huang and Yu, 2013)

23
Q

What are the two main reasons why liquefaction occurred 350-400km away from the epicenter in Tokyo bay during the 2011 Tohoku EQ (Authors in Authors)?

A

(1) deposits were fill materials/young alluvium (2) duration of EQ was up to 300 s (Bhattacharya et al, 2011 in Huang and Yu, 2013)

24
Q

Why was it that gravely soils were once thought to be unliquefiable (Authors)?

A

Because they had high hydraulic conductivity (Huang and Yu, 2013)

25
Q

Give an example where gravely soils were liquefied (grain sizes) (Authors in Authors)

A

2008 Wenchuan EQ, mean grain sizes of 1 to >30mm (Cao et al, 2011 in Huang and Yu, 2013).

26
Q

What is thought to be the reason as to why gravely soils were liquefied during the 2008 Wenchuan EQ (Authors in Authors)?

A

The soils were shallow and loose (Huang and Yu, 2013)

27
Q

So far, liquefaction has not been found deeper than __ m

A

30m

28
Q

What are the two coupling factors thought to contribute to very deeply occurring liquefaction (Authors)?

A

High amplitude ground motion with long duration (Huang and Yu, 2013)

29
Q

How deep was liquefaction found in the Tohoku 2011 earthquake? (Authors in authors)

A

12-16 m (Bhattacharya et al, 2011)

30
Q

Up to what depths is liquefaction normally expected to occur? (Authors)

A

Up to 6 m (Huang and Yu, 2013)

31
Q

What would a vertical profile of a region at high risk of liquefaction look like (two layers)(Authors)

A

A saturated sandy layer overlain by confining medium such as clay or silt (Huang and Yu, 2013)

32
Q

What is the most common feature of re-liquefaction during aftershocks? (Authors in Authors)

A

Stacked sand volcanoes re-liquefying, small holes developing in larger holes (Huang and Yu, 2013)

33
Q

Give an example of re-liquefaction during an aftershock (Authors in Authors)

A

2008 Wenchuan EQ, re-liquified during Ms 6.4 (Chen et al, 2009 in Huang and Yu, 2013)

34
Q

In what situation can unsaturated soil liquefy fully?

A

pore air and water pressure = confining pressure (Huang and Yu, 2013)

35
Q

What are the three main ways damage can be induced on buildings by liquefaction (Authors)?

A

Ground subsidence, lateral spread, buoyancy (Huang and Yu, 2013)

36
Q

What are the two ways that damage caused by buoyancy during liquefaction be avoided? (Authors in Authors)

A

Ground improvement methods, anchoring of utilities (Huang and Yu, 2013)

37
Q

According to (Authors) how many fires were alight at one point in Kobe, 1995?

A

148 (NFPA, 1995)

38
Q

What did (Authors) state as a potential ignition source during the Kobe 1995 EQ?

A

Open fires in houses commonly used for cooking and heating (NFPA, 1995)

39
Q

Name three factors which worsened the fire situation in Kobe according to (Authors)

A

Tightly knit houses made from lightwoods, compromised water supply, limited road access

40
Q

Name three reasons why fires were not as bad as they could have possibly been according to (Authors)

A

Low windspeed up to 3 days after EQ, Kerosene fires used for heating generally turned off due to early hour of EQ, Some buildings stood in the open/had structures were harder to penetrate (NFPA, 1995)

41
Q

Name a case study where landslides triggered by earthquakes proved fatal (Authors)

A

Mount Huascaran, Peru, 1970

42
Q

What was the death toll at Mount Huaschran, Peru?

A

25,000

43
Q

Where did most of the deaths occur?

A

Towns of Yungay and Ranrahircha

44
Q

The town of Yungay is ___km from Mount Huaschran

A

16.2km

45
Q

Give an example where a flood has been caused by a landslide into a water body, and explain what happened, number of fatalities.

A

1933 Deixi, China: Landslide damed river to 255m high, then the dam failed. 2500 drowned.

323: Geological Hazards (7 decks)

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