WAVE problem; Earthquakes produce two kinds of seismic waves: the longitudinal primary waves...?
Earthquakes produce two kinds of seismic
waves: he longitudinal primary waves (called
P waves) and the transverse secondary waves
(called S waves). Both S waves and P waves
travel through Earth’s crust and mantle, but
at different speeds; the P waves are always
faster than the S waves, but their exact speeds
depend on depth and location. For the purpose
of this exercise, we assume the P wave’s
speed to be 8740 m/s while the S waves travel
at a slower speed of 4100 m/s.
If a seismic station detects a P wave and
then 47.4 s later detects an S wave, how far away is the earthquake center?
Answer in units of km.
Earthquakes produce two kinds of seismic
waves: he longitudinal primary waves (called
P waves) and the transverse secondary waves
(called S waves). Both S waves and P waves
travel through Earth’s crust and mantle, but
at different speeds; the P waves are always
faster than the S waves, but their exact speeds
depend on depth and location. For the purpose
of this exercise, we assume the P wave’s
speed to be 8740 m/s while the S waves travel
at a slower speed of 4100 m/s.
If a seismic station detects a P wave and
then 47.4 s later detects an S wave, how far away is the earthquake center?
Answer in units of km.
1 Answer
Explanation:
distance = speed * time
here, the distance is from the earthquake centre to the seismic station.
both the P and S waves travel from the earthquake centre before being detected by the seismic station, so the distance is the same for both.
the speeds are given as
we also know that the P wave arrives
we do not know the time that the P wave takes to travel, but we can denote it as
the time that the S wave takes to travel can be denoted as
for the S wave, speed * time is
for the P wave, speed * time is
since the distances that they travel are the same, the two expressions for speed * time are equal.
if you expand the brackets, you can find that
then you can subtract
and divide by
since distance = speed * time, the distance that the P wave travels is
this is
in kilometres, this is