The name of my science fair project is: Determining which soil type is the most susceptible to longitudinal waves in order to prevent earthquake damage. The goal of the experiment was to find which soil had the most displacement after being exposed to longitudinal waves.

I came up with this idea after learning about longitudinal waves in my 8th grade science class. During the lesson, we touched on waves traveling through mediums and although we didn’t go deep into the topic, it sparked my interest. We talked about how they would travel through solids, gases, and liquids differently, but I wanted to focus on how they traveled through different soil types, as that would no doubt have an effect on the damage caused by longitudinal waves in earthquakes.

Before I did any experimenting, I had to do background research. I looked at many different sources that explained the effect of properties of soil on the movement of longitudinal waves through them. My research led me to hypothesize that the sand would have the highest displacement, as it is a more unstable soil type.

Now that I had more knowledge on the topic, I could start setting up the experiment. I already had an aquarium tank (from a previous experiment) that I could put the dirt in and a speaker to play the frequencies from, but I still needed to acquire the soils, so my dad, Ahmad Siddiqui, and I went to the Home Depot to get them. From there, we bought a bag of potting mix and a bag of sand. We couldn’t find a third type to use, so we went home and got some dirt from our backyard. This could also serve as a local soil type and allowed me to shift the focus of the project to specifically Texas.

As this experiment required mimicking an earthquake, I started looking into frequency generator apps to play the frequencies, but none worked as well and easily as this website, which can play the desired frequency with a simple slider. I connected our Dell speaker which would imitate the epicenter (the initial point of collision of tectonic plates that the vibrations emulate from) of the earthquake to the computer and started playing the frequencies to see if it worked. The speaker successfully played them, but only when it was at full volume. The frequencies I chose to use: 50, 75, and 100 Hz, were chosen because I found that an average earthquake’s frequency is between 50 and 100 hz. I also found that the average length is from 10-30 seconds, but I chose to keep that a constant at 20 seconds to decrease variables.

I still needed to do one more thing before starting the experiment, which was setting up the ADXL345 accelerometer. The first time I ordered the accelerometer, I realized an important port was missing, so I ordered it again, and finally got the right one. I already had an Elegoo unoR3 from a circuitry kit, so I used that to connect the accelerometer to the computer. To connect the accelerometer to the UnoR3, I used female-to-male DuPont wires and matched up the required ports using a YouTube tutorial. 

Coding the accelerometer was the longest and most difficult part out of the whole experiment. I had actually attempted this project in 8th grade, but got stuck on this part, so I had given up and done a different experiment. I came back in 9th grade thinking that I had more experience which would help me code it, but the only issue that had prevented the code from working earlier was that the setting on the serial monitor did not match up to the code. I was really frustrated with myself for not noticing that, as the code itself was quite simple and easy to understand.

Now it was time to put everything in the tank. First, I placed the connected speaker in the end of the tank. Then, I put the accelerometer (also connected to the computer) on the other side. Finally, I filled the tank with 30 pounds of sand and began experimentation. 

I started by writing down the coordinates from the serial monitor which displayed live readings from the accelerometer. Then I would play the 3 frequencies for 20 seconds each. I wrote down the coordinates as the vibrations played and repeated this 3 times for every frequency. At the end, I took the average of the 3 trials. After I calculated the averages, I subtracted them from the base coordinates I had written down at the beginning to get the displacement.

After I finished the sand experiment, I completed the process again for the other two soil types. 

The final results were that the potting mix had the highest displacement and the soil from my backyard had the lowest. I wasn’t surprised that the soil from my backyard had the lowest, as Texas soil is like clay and clumps very easily, however I was surprised that the potting mix had a higher displacement than the sand. After reflecting on my observations from during the experiment, I came to the conclusion that this occurred because the weather was a little humid the day that I conducted the sand experiment, and this may have caused the sand to clump and transmit less vibrations. Also, during the potting mix experiment, I noticed that the soil was visibly vibrating, while neither of the other soils were doing so. This was due to the potting mix not having the ability to clump easily and having individual pieces.

My hypothesis was rejected, as I hypothesized the sand would have the highest displacement, and it was actually the potting mix that had the highest displacement.

The results from this experiment can be used to strengthen safety procedures. This can be done by having the soil of different areas tested for stability, and if the soil is weak, the people living in that area can create safety procedures for what to do in the event of an earthquake.

In the future, I might expand on this experiment by using a larger variety of soil types including samples taken from different areas around the world, and test to see what properties the soils have, and if they are stable. I can also expand this by placing the accelerometer in different areas of the tank and comparing the coordinates to other locations to see how the waves travel over time, and at what point they are no longer harmful.

I went on to conduct further research into the best earthquake safe material, which is steel. Steel can be used in areas where there are frequent and high damage earthquakes to reinforce buildings. It can be implemented through the use of beams, cladding, and mesh, and is durable due to its properties that will cause it to bend rather than break when exposed to seismic vibrations.

Overall, I learned a lot during this experiment. I went on to win first place at school, second place at district, and Honorable mention at regional, with a special award for Geoscience Excellence from the Association for Women Geoscientists. I was also one of ten in my category selected to compete at Texas Junior Academy of Science where I received an Honorable Mention.

I hope to utilize the suggestions judges have given me at each fair, and create a project that can take me to state, national, and even international one day.

If you have any questions, or want some advice on your science fair project, feel free to contact me!