Lesson Earthquake waves

This Lesson (Earthquake waves) was created by by ikleyn(52775)

: View Source, Show
About ikleyn:

Earthquake waves

Problem 1

Seismographs can record two types of wave energy (P-waves and S-waves) that travel through the Earth
after an earthquake. Traveling through granite, P-waves travel approximately 5 km/sec and S-waves travel approximately 3 km/sec.
If a geologist working at a seismic station measures a time difference of 40 sec between an earthquake's P-waves and S-waves,
how far from the epicenter of the earthquake is the station?

Solution

Let d be the distance from the epicenter of the earthquake to the station (in kilometers).


For P-wave, the traveling time is   seconds.


For S-wave, the traveling time is   seconds.


The difference is


     -  = 40  seconds.


It is your "time" equation.


To solve it, multiply all terms by 15 = 3*5.  You will get


    5d - 3d = 15*40

    2d = 600

    d = 300 kilometers.


ANSWER.  The distance from the epicenter of the earthquake to the station is 300 kilometers.

Problem 2

The primary wave of an earthquake travels 1.7 times faster than the secondary wave.
Assuming that the secondary wave travels at 275 km per min and that the primary wave is recorded at a seismic station
5.07 minutes before the secondary wave, how far from the station was the earthquake?

Solution

Time for the secondary wave from the source to to the station is    minutes, where d is the distance from the source to the station.


Time for the primary wave from the source to to the station is    minutes, where d is the same distance from the source to the station.


Your equation is


 -  = 5.07 minutes   (the "time difference" equation).


From the equation


d =  = (at this point I use Excel spreadsheet in my computer) = 3386 kilometers.


Answer.  The distance from the source to the station is 3386 kilometers.

My other additional lessons on Travel and Distance problems in this site are
    - A child is running on a moving sidewalk in an airport
    - Climbing a coconut tree up and down
    - A rabbit and a dog
    - Two runners run on a quarter-mile oval track
    - In a 2-mile race competition
    - Two runners on a circular track
    - Unusual catching-up problem
    - Unexpectedly simple solutions to standard catching up problems
    - HOW TO algebreze and to solve these non-traditional Travel and Distance problems
    - Two cars and a train make a race
    - One very twisted Travel and Distance problem
    - The buses and a traveler
    - Time equation: HOW TO use, HOW TO write and HOW TO solve it
    - Problem on determining the maximum flight distance using time equation
    - One entertainment problem on Time equation
    - Miles per gallon effectiveness and moving car
    - How many mail trucks will a mail truck meet on its trip
    - One unusual Upstream and Downstream Travel problem
    - How the state patrol officers on a highway could detect the driver exceeded the speed limit
    - Two ships traveling on parallel courses in a foggy day
    - Moving escalator problems
    - Advanced Travel and Distance problems for bodies traveling toward each other
    - Olympiad level problems on Travel and Distance
    - Upper league Travel and Distance problems
    - Additional entertainment Travel & Distance problems
    - OVERVIEW of additional lessons on Travel and Distance

Use this file/link ALGEBRA-I - YOUR ONLINE TEXTBOOK to navigate over all topics and lessons of the online textbook ALGEBRA-I.

This lesson has been accessed 1655 times.