WJEC – Geology of the Human Environment (GL3) – May 2004
1.Crustal deformation can be used in the prediction of earthquakes by measuring
changes in the distance between two fixed points along a survey line.
Figure 1a is a map of central California showing survey lines (A - E) across the San Andreas Fault system. Figure 1b shows the changes in the lengths of these survey lines over time.
Source: Earthquakes - Bolt (Freeman)
Figure 1a Figure 1b
Refer to Figures 1a and 1b
(a)(i)State the major difference to changes in the length of survey
lines A and B between 1959 and 1969.[1]
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(ii)Calculate the average rate of change in the length of survey
line B for the 10 year period (1959 – 1969).
Show your working.
……………………………….cm/year.[2]
(iii)Compare the average rate of change in the length of survey line
C with that for survey line B over the same period. Account
for the difference.[3]
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(b)Using the data, draw two arrows in the box on Figure 1a, to show the direction of relative movement on either side of the Hayward fault. Explain the evidence from the survey lines for your answer. [2]
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(c)Explain how this type of survey might enable earthquakes to be
predicted.[2]
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(d) From you knowledge, explain one other method used to predict earthquakes [3]
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Total 13 marks
Notes for answers
These represent suggested answers and do not necessarily represent all the possible acceptable alternatives of a mark scheme.
Question 1
(a)(i)A - decreases
B - increases - (numbers accepted)[1]
(ii)1959 - 0 cm
1969 - 20 cm (range 20-22)
20cm/10years = +2cm/yr [2]
(iii)C - little/no significant change in length
C - both ends of survey line on same fault block
B - crosses the fault/extension
[3]
(b)Arrows showing dextral strike slip
D - shows extension over time [2]
(c)Reduction in extension or compression along a survey line
shows build up of stress
Seismic gap
Some move faster than others, change in rate
Thus increase chance of an earthquake
(Max 2 marks)[2]
(d)One explained from:
groundwater levels/pressure
tilting/ground elevation
radon gas emissions
electromagnetic signals
electrical resistivity
animal behaviour
earthquake lights
changes in seismic activity/seismic gap.
Other appropriate explained
(Max 3 marks)[3]
Total 13 marks
ESTA would like to thank the WJEC for allowing this question to be published on GEOTREX. Any comments should be directed to the Subject Officer for Geology at the WJEC. 15/04/2007