Make a tabletop model of an earthquake trace

Hang a light marker so it touches a strip of paper loosely. Let one person pull the strip steadily while another moves its support sideways in short pulses.

Ask one person to move a paper strip while a second taps its support sideways. End with a short account linking the changed condition, the observation, and its likely explanation. Include one uncertainty that would matter if you repeated it. This separates the physical idea explored by the demonstration from limits created by a household setup and gives another person a way to test the same claim.

Two similar pulses can appear farther apart when the paper is pulled faster. Observe the setup from the same place in each trial. A view from farther away can hide a shallow curve or make two positions look aligned. A short guide mark shows the place you used. Keep the recording method fixed as well when changing the setup itself is the point of the comparison.

Compare sections made during steady pulling with sections made during shaking. A wider pattern can reflect a larger lateral movement in this particular setup.

A marker that stops touching produces gaps that resemble pauses in motion. Write one prediction alongside the setup. It helps to describe what would be observed if that prediction were right, including a direction, a clearer pattern or a measurable difference. This makes room for the outcome to disagree with what you expected and gives you a better question for a second run.

Adjust contact and run a straight baseline before trying a new sequence. Decide how to mark an observation when two readings fall too close together to separate. Even spacing on a sheet is useful only to the extent you can see where a feature crosses each line. A visible range can carry more meaning than a single estimated digit that your instrument cannot resolve.

Label any deliberate changes of speed along the edge of the completed trace. Repeat a simple comparison and keep the starting conditions as similar as the setup allows. Where a ruler, timer, or camera is involved, read it in the same way each time. A handful of consistent observations is easier to interpret than a long list collected under changing conditions.

Write a row for each run and keep apparently odd results in the record. Mark things that went wrong, such as a shifted surface, uneven starting point or missed time, before judging the pattern. Changing how you record the behaviour halfway through can make two otherwise similar trials difficult to compare. Explain the outcome in a sentence that a reader can check against the figures or sketch. Use a second sentence for a proposed cause. If you can imagine a different cause that fits the same observations, describe a small test that would help distinguish the two. Comparing those predictions can make a follow-up clearer than simply repeating the same demonstration. Show the direction in which the paper moved before interpreting the squiggles. Turning a trace around can reverse the apparent order of its pulses. Write the independent change at the start of each row and keep the outcome beside it. Include anything about a failed run that would matter to somebody repeating the setup. If you later make a neat graph, keep the rough record as well so it remains possible to inspect the reasons for leaving out a point.

Try changing the pulling speed while keeping the shaking as similar as possible, then compare the spacing. Sketch your apparatus before you start and use the sketch to identify where each observation will be made. Write down the starting state before changing it. If another person repeats the trial, knowing the relative positions can matter more than the brand or appearance of the materials.