ISL #15
Earthquake Patterns and Plate Boundaries
Integrated Science 4
05/15
Name:
Per:
 Objective
Use the IRIS Earthquake Browser to explore earthquake patterns at all three types of plate tectonic boundaries and
identify their relationship to geomorphological features (mountain chains, volcanoes, trenches) associated with each plate
boundary.
 Procedures
1. Global Seismicity: Preliminary Observations
Google the following
phrase to access the IRIS
earthquake map: “iris
earthquake browser”. You
will use this web
application to plot
earthquake data. When
you open the website, you
will be presented with a
map of the world and the
200 most recent
earthquake events.
Try to zoom in on the map,
move it around, and click on events to get more details about particular earthquakes. On the right-hand side of the
window, try change the number of events, time, magnitude, and depth ranges of events that are displayed on the map. In
the upper right-hand corner, try to change the view from geopolitical boundaries to satellite or terrain. Please note:
Displaying large numbers of events (over 3,000) may cause browsers on slower machines to stall or freeze up. Keep this in mind when
plotting data.
 Questions
1.
How can you change the settings to give you a better idea of where plate boundaries may be?
2.
How many large earthquakes (≥9.0 magnitude) have occurred in the past ten years (you'll need to change the time range
– “earliest available” changes to today's date ten years ago)? How many ≥7.0 magnitude? How many in total (look at
“events displayed xxx of xxx. The second number is the total)?
3.
Where do the deepest earthquakes (≥300 km) tend to occur?
4.
Switch to a satellite view of the world. Do earthquake patterns correlate with any visible features? If so, describe
the correlations.
5.
Which earthquakes are most common: deep or shallow?
2. Convergent Boundaries (Continent – Ocean Collision)
You will now explore the
seismicity of a plate boundary
between ocean and continental
crust. In the lower left-hand
corner, click "Select a region",
then draw a box over Japan,
including some of the nearby
ocean. Select the following
settings and click “Zoom to
region”:
Location: An area containing North
Korea, South Korea, Japan, into
Pacific Ocean
View: Satellite
Display: 1000 events
Time Range: Set the dates to
request 2 years of data (from this
date last year through latest
available).
Magnitude Range: All Values
Depth Range (km): All Values
You should get a map that looks similar to the one above (if you've been playing around with the magnitude and depth
ranges, the numbers may not look exactly as above, which is fine as long as the "All Values" boxes are checked).

6.
Questions
How frequent are earthquakes in this region?
7.
What is the depth distribution of the earthquakes? Is there a pattern in the earthquake depths? If so, how do you
explain it?
8.
Do the earthquakes correspond to any visible features in satellite view? If so, what are these features?
3. Divergent Boundaries (Mid-Ocean Ridge)
You will now explore the seismicity of a
divergent boundary in the central Atlantic, the
mid-ocean ridge. Click "Select a region", then
select a large area of the central Atlantic and click
“Zoom to region”.
Location: Middle of Atlantic Ocean (e.g. from eastern
edge of Brazil to western edge of Guinea in Africa)
View: Satellite
Display: 1000 events
Time Range: Set the dates to request 2 years of
data (from this date last year through latest
available).
Magnitude Range: All Values
Depth Range (km): All Values
 Questions
9.
How frequent are earthquakes in this region? How does this compare to the seismicity near Japan?
10.
What is the typical depth of earthquakes in this region? How does this compare to earthquakes near Japan?
11.
How do you explain the differences in depth and frequency of earthquakes between the mid-ocean ridge and
Japan?
12.
Do the earthquakes correspond to any visible features in satellite view? If so, what are these features?
4. Transform Boundary (California's San Andreas Fault)
You will now explore the seismicity of a
transform boundary in California, the San
Andreas Fault. Click "Select a region", then
select a large area including California and
all of Mexico click “Zoom to region”.
View: Satellite
Display: 1000 events
Time Range: Earliest available to latest
available
Magnitude Range: All Values
Depth Range (km): All Values
 Questions
13.
Do earthquakes in California tend to be deep or shallow?
14.
Of the types of boundaries investigated earlier, which one best explains the pattern you see in Central America?
15.
Why would earthquake depths be different in California and Central America?
16.
How many large earthquakes of magnitude ≥7 occurred in California? In Central America?