Here's What Earthquakes Look Like From Inside the Earth
Is it possible to “hear” an earthquake? Not the rumbling of the ground that results, but the earthquake itself. Even if you could, what’s the point of listening?
About a dozen years ago, geophysicist Ben Holtzman and musician/sound designer Jason Candler set out to answer these questions, with a side goal of sharing their passion for earthquakes with the public. From the fruits of their research, the SeismoDome show was born.
Holtzman and Candler co-produce the show—with Holtzman writing scientific content, creating sounds from seismic data, and working with collaborators to produce the visual elements, while Candler handles the sound engineering and design and helps with the writing and conception of the show.
When asked what listening to earthquakes can contribute to our knowledge of them, Holtzman explains how our subconscious factors in: “Humans perceive an enormous amount of information about physical processes through sound; we do it all the time, mostly subconsciously,” he says. “Interpreting footsteps and motor sounds, doors opening—this processing becomes conscious when we do not know what the sound is.”
So, where do earthquakes come in? Holtzman says seismic data is almost completely inaudible if played at its natural speed, and the frequencies of large earthquakes aren’t even within our hearing range. However, if the frequency is shifted up, a much wider range of sounds can be heard. These sounds can vary a great deal depending on how close the seismometer was to the earthquake source, as well as the magnitude of the earthquake.
The traditional way of understanding earthquakes is to examine a chart made by a seismograph: squiggles on a page that convey the characteristics of the Earth’s movement. But that is lacking in meaning and context, says Holtzman. Instead, people can take advantage of our natural ability to compare sounds and interpret meaning from them.
As Holtzman puts it, “the data come to life.”
Holtzman adds that the closer to the epicenter the data is recorded, the more details they are able to pick up. For example, the crust adjusting and settling into its new configuration after a large earthquake. Moving further away from the source can detract from the sharpness and clarity.
“Further down the spectrum, we can listen to the surface waves,” says Holtzman. “When these waves are sped up more, they sound like slow chirps, and sometimes even like whale songs. There is a clear physical explanation for the chirp (rising frequency with time). So hearing the sound, and then the explanation, gives people a visceral experience to attach the physical meaning to.”
Holtzman and Candler use the SeismoDome project to explain concepts like surface waves and plate tectonics, in order to educate people not just about earthquakes, but also what earthquakes tell us about the Earth more broadly.
“Our aim is to demystify earthquakes, but more importantly to get people to see them as a natural process,” explains Holtzman. He goes on to say that the vast majority of earthquakes do not hurt anyone, and that learning more about the natural phenomena can help us understand how and where to build our cities to prevent damage.
Holtzman adds, “because large earthquakes repeat on time scales that can be longer than our generational memories, people lose sight of the hazard. Most societies don’t have the resources to take these hazards into consideration when planning cities and building buildings.”
Holtzman and Candler also test our perception of time. Playing with our narrow band of perception, they compress more and more “earth time” into each sound and video, ranging from a few hours to a few years. By the end of the show, their goal is to pull the crowd’s sense of their spatial and temporal scale so much that they think about their own lives differently—how small we are and how short our lives are, but not with the intent of conveying insignificance. Says Holtzman, “quite the opposite.”