Travel-Time Curves

Time is a measure of a sequence of events. It never stops and is always ongoing. Time is measured by a clock.

We can measure time using different units from seconds to minutes, hours, days and even weeks months and years though time is usually expressed in hours and minutes. Time can be measured by a 12 or a 24 hour clock. The 12 hour clock is also referred to as AM / PM.

Examples of time:

Using the 12 hour clock - We go to school at 8:00 AM.
Using the 12 hour clock - We ate lunch at 1:00 PM.
Using the 24 hour clock - We ate lunch at 13:00.


Time can be converted from one unit to another. Here is the conversion factor list.
60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1 day
7 days = 1 week
365 days = 1 year

Activity 1:

Study the following table and see how many items you can express correctly:

Time as we express it in words

Time using the 24 hour clock

Time using the 12 hour clock

Seven o’clock in the evening 19:00 07:00 pm
Quarter to ten in the morning 09:45 09:45 am
Twenty past three in the afternoon 15:20 03:20 pm
Quarter past eight in the evening 20:15 8:15 pm
Midnight 00:00 12:00 am
Midday 12:00 12:00 pm
20 past 7 in the evening 19:20 07:20 pm
Ten to two in the morning 01:50 01:50 am
Ten to two in the afternoon 13:50 1:50 pm

Did you know a leap year has 366 days and it occurs once in 4 years. You can determine if a year is a leap year by dividing it by 4.

For example:

The year 2000 was a leap year because 2000 ÷ 4 = 500
The year 2004 was a leap year because 2004 ÷ 4 = 501

The year 2001 was not a leap year as it is not exactly divisible by 4.

Test your skills
Question: How many minutes are there in 2 hours?
(Answer: 2 * 60 = 120 minutes)

Question: How many hours are there in 3 days?
(Answer: 3 * 24 = 72 hours)

Did you know?

A Travel time curve seismic is a curve of the time that it takes for seismic waves to travel from the epicenter of an earthquake to measuring stations.

Scientists all over the world make use of the seismic data to develop an approximate model of the earth’s interior. During an earthquake, these waves are generated at a much higher velocity than usual. Depending upon these velocities, the seismic waves travel from the source to different parts of the world.

The arrival times at separate points are recorded as a function of the measure of distance from the source of seismic activity. These arrival times which are generally in the form of S or P waves are depicted graphically in the form of travel time curve seismic.

Within the earth, the velocity of the seismic activity can be computed accurately by the slopes of the curves on this graphical representation.


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