To locate an earthquake epicenter using triangulation, seismologists determine the S-P interval from seismograms of at least three seismic stations. This interval is converted to epicentral distance and circles are drawn on a map with radii equal to these distances. The intersection of these circles identifies the epicenter. Triangulation is suitable for local quakes, while distance-time graphs are used for more distant quakes. Locating epicenters helps identify active fault lines and areas at risk for future major quakes due to long periods of inactivity on certain faults.

1. Analysis
Earth and Space
M1A1
By: T. Alfred Gico

2. 1. What do you need to
determine in order to locate
the epicenter of an earthquake
using triangulation
method?

3.  determine the time interval
between the arrival of the P and
S waves (the S-P interval) on the
seismograms from at least three
different stations.
measure the interval to the
closest second and then use a
graph (Distance-time graph) to
convert the S-P interval to the
epicentral distance.

4. 2. You draw a circle to
represent each distance on a
map.
What does the radii of circles
represents?

5.  The radius of each circle
corresponds to the epicentral
distance for each seismic
recording station.

6. 1.What is the difference of
using triangulation method
to distance -time graph in
determining the epicenter of
the earthquake?

7. Triangulation method
-appropriate to use in
locating epicenter in an
earthquake happened locally
Distance – time Graph
- use by seismologist in
determining location of
epicenter of an earthquake in
greater distance

8. ..Earthquake Epicenter
Triangulation.mp4

9. GENERALIZATION
Triangulation Method
Uses distance information from three seismic
stations
to locate the earthquake epicenter
To locate:
 Determine the time interval between the
arrival of the
P and S waves on the seismogram
from three
different stations
 Measure the interval closest to seconds

10.  Using epicentral distances, draw
circles to represent distance on
map. Radius of each circle
corresponds to epicentral distance
for each seismic recording station.
 Three circles will intersect at
one point that locates the
epicenter of an earthquake.

12. Locating earthquake epicenters will
pinpoint which fault lines are active.
- less active fault lines stores great
amount of energy that
could cause major earthquake once
released.
- places near fault lines that remain
inactive for a long period time are
due to experience a major
earthquake

13. Epicenter-
The point on
the Earth's
surface
located
directly
above the
focus of an
earthquake.
Focus-The location where the earthquake
begins. The ground ruptures at this spot,
then seismic waves radiate outward in all
directions.

14. Good
DAY!