**Earthquake Model**

***Description, Technical Specifications & Demonstrations***

**This website details the model made by Ross Stein and demonstrated
most recently at the May 2000 USGS Open House by the Earthquake Hazards
Team. The website has been constructed due to the great public interest
shown at the Open House, particularly by teachers.**

**This website includes an [animation]{.underline} and
[photographs]{.underline} of the model \'in action\', a lengthy [model
description]{.underline}, and associated [diagrams]{.underline}.  It
also includes [technical specifications]{.underline} (bottom of this
page) to aid those wishing to build their own model.**

**Model Description**

The following is a description of Ross Stein\'s \"spring and rider\"
(also known as the \"brick and bungee\") earthquake simulation machine.

The apparatus consists of a wooden board 3-4 feet in length with a winch
on one end.  There is a pulley leading from the winch to the brick that
is oriented so that the force acting on the brick has no vertical
component. The board has a strip of sandpaper down half of it to
increase friction.

Two types of material connect a brick to the winch. The first is a
non-stretching cord, which is used to ensure that all of the accumulated
stress is transferred into the second material - surgical rubber
tubing.  This tubing is connected directly to the brick and is extremely
elastic, which allows stress to build when the crank on the winch is
turned.  The brick also has a strip of sandpaper on one side, for
additional friction.  This is the basic set-up of the experiment.

With this, students can mark off \"rupture length\" during each
\"earthquake\" by seeing how far the brick slips.  They likely will find
that the lengths are not consistent.  They may also wish to time the
\"earthquakes\" assuming a constant speed by the person turning the
crank. Again, time is not always consistent either.  If they turn the
crank slowly as the cord nears \"failure\" they may hear the sandpaper
crackle a moment before the brick moves, thus simulating a foreshock.

There are some accessories to this model as well.  The first is talcum
powder, which can be sprinkled on the board next to the sandpaper. When
the brick is placed on the powder (the side of the brick without the
sandpaper) students will observe an almost constant rate of motion. 
This simulates creeping faults, such as is found on part of the San
Andreas. An additional brick is included in the demonstration as well. 
This may be stacked atop the first brick to produce larger
\"earthquakes.\"  It can also be removed from atop the first brick just
at the moment of failure to show that slippage can occur even without
additional stress, just by removing the additional brick.

Finally, the second brick is equipped with surgical tubing as well, so
the two can be placed on the board in tandem.  In this way, the machine
demonstrates how earthquakes \"talk\" to each other.  When stress is
sufficient, the first brick moves forward, increasing stress on the
second brick.  Eventually the second brick slips, reducing the backwards
force on the first brick, and the first brick can slip again.

One additional accessory for the machine is a mass balance that can be
used as a strain gauge.  Although it was previously shown that
earthquakes are not consistent with time or in their rupture length, the
brick tends to slip at the same reading on the gauge. With this set-up
and the various accessories, this demonstration can show a variety of
earthquake concepts.  If the students use the mass balance to weigh the
bricks, they can calculate the coefficient of friction on the board, and
predict what force is necessary to cause an \"earthquake.\"

Despite being relatively simple and elegant, the machine is remarkably 
true to the actual earth.  Thus students get a fun, hands-on look at
stress and rupture  in the laboratory.

# Diagrams

![](media/image1.jpeg){width="5.932638888888889in" height="8.51875in"}

# Technical Specifications

![](media/image2.jpeg){width="5.804166666666666in"
height="2.063888888888889in"}

Text, Diagrams and Page Design by D.G. Cornwell & S.T. Detweiler, May
2000.

The USGS library maintains a wonderful teacher resource facility with
materials any teacher can check out.

Tel 1-650 329 5026 or 5028, USGS Library on Survey lane off 345
Middlefield Road, Menlo Park

(map http://online.wr.usgs.gov/kiosk/mparea3.html)