Earth and Environmental Science 11–12 · Year 11
Stick-slip on a brick: elastic energy storage and sudden release as an earthquake model
Module 3: Energy Transformations
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The idea
Rock across a locked fault stores elastic potential energy until friction fails, and the sudden slip releases that energy as seismic waves.
What you need
- three or four house bricks with an elastic rope or coiled spring tied to the middle brick (Earthlearningidea Earthquake prediction), or one brick on coarse sandpaper taped to the bench
- a spring balance of suitable range (for example 0 to 50 N) or a force sensor, and a set of masses to calibrate the elastic
- metre rule, marker, stopwatch
How to do it
- Set up the bricks as in the Earthlearningidea sheet (holding the front brick still if it slides), attach the elastic or spring and pull its free end at a steady slow rate with the balance in line.
- Record the balance reading and the stretch just before each slip, and the distance the top brick moves.
- Repeat for 10 slips at the same pulling rate; then change the surface (sandpaper against smooth) and repeat.
- Calibrate the elastic by hanging known masses, find k, weigh the sliding brick for the model's mass input, and calculate the elastic energy stored before each slip, E = ½ k x².
- Plot slip distance against stored energy and comment on whether the slips are predictable.
What you should see
The bricks stay still while the force climbs, then slip suddenly when it reaches the static friction limit, and the force drops; the timing and size of the slips vary from run to run at the same pulling rate, which the Earthlearningidea sheet notes are rarely consistent. The stored energy at each slip is E = ½ k x² from the learner's own k and stretch; in the spring-slider model with its default inputs (k = 50 N/m, μ_s = 0.6, a 3.0 kg load) slip starts at 17.7 N, a stretch of 0.353 m, storing 3.12 J. In the spring-slider model a larger stretch at failure gives a longer slip, but the moment of failure cannot be predicted from the force alone.
What changes
- What you change
- surface roughness (sandpaper or smooth)
- What you measure
- force at slip and slip distance
- What you keep the same
- same pull rate
- same elastic
- same bricks
- same starting position
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Earthquakes happen because the ground is hollow underneath.
- Faults move smoothly all the time (some creep, most lock and slip).
Safety card
Hazards
- bricks sliding onto fingers or feet
- elastic recoil
Controls
- keep hands clear of the slip path
- pull along the bench, not upward
- closed shoes
Note
No hazardous chemicals or heat sources: record the activity in the school's RiskAssess risk assessment, following the NSW Department of Education Science safety and compliance page; the Chemical Safety in Schools package is not triggered.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES11-10EES11/12-5EES11/12-6EES11/12-7
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-02
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.
- www.nsw.gov.au/education-and-training/nesa/curriculum/science/earth-and-environmental-science-stage-6-2017
- www.earthlearningidea.com/PDF/49_Earthquake_prediction.pdf
- www.earthlearningidea.com/PDF/415_Slip_sliding_away.pdf
- www.ga.gov.au/education/classroom-resources/earthquakes-teacher-notes-and-student-activities