Concept explainers
Earthquake The graph shows the vertical acceleration of the ground from the 1994 Northridge earthquake in Los Angeles, as measured by a seismograph. (Here t represents the time in seconds.)
- (a) At what time t did the earthquake first make noticeable movements of the earth?
- (b) At what time t did the earthquake seem to end?
- (c) At what time t was the maximum intensity of the earthquake reached?
(a)
The time at which the earthquake first make the noticeable movements of the earth.
Answer to Problem 44E
The first noticeable movement took place after 5 seconds.
Explanation of Solution
A graph is given which shows the vertical acceleration of the ground from an earthquake as measured by a seismograph.
Figure (1)
The acceleration is given on vertical axis and the time in seconds on horizontal axis.
From Figure (1), it is noticed that the acceleration of ground is there right after 5 seconds.
Therefore, the first noticeable movement took place after 5 seconds.
(b)
At what time the earthquake ended.
Answer to Problem 44E
The earthquake ended after 30 seconds.
Explanation of Solution
A graph is given which shows the vertical acceleration of the ground from an earthquake as measured by a seismograph.
Figure (1)
From Figure (1), it is noticed that there is no acceleration of the ground after 30 seconds. It clearly means that the earthquake stopped after 30 seconds.
Therefore, the earthquake ended in 30 seconds.
(c)
At what time the earthquake had maximum intensity.
Answer to Problem 44E
The maximum intensity of the earthquake was reached after 17 seconds.
Explanation of Solution
A graph is given which shows the vertical acceleration of the ground from an earthquake as measured by a seismograph.
Figure (1)
Locate the local maximum point to find the time at which earthquake had the maximum intensity.
The value
From the Figure (1), it is noticed that the value of acceleration is maximum between
The acceleration is more than
This is the point of local maximum.
Therefore, the maximum intensity of the earthquake was reached after 17 seconds.
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