Imagine trying to solve a mystery by studying the traffic patterns of coworkers arriving home from work, without knowing their exact routes or any other details about them. This analogy illustrates the process used in seismology to create images of magma reservoirs beneath Yellowstone Caldera.
Scientists use “tomography,” which involves measuring seismic waves generated by earthquakes and analyzing how they travel through different regions of rock. By working backwards from the measured data, researchers can infer a plausible model of the conditions underground that would cause those patterns.
One common method is to measure the time it takes for seismic waves to reach seismometers, noting where they arrive “late.” This allows for mapping out areas with different physical properties, such as temperature, rock type, and density. The more data collected from multiple sources, including earthquakes, instruments like seismometers, and even magnetotelluric instruments, the better the resolution of the map.
In Yellowstone’s recent study, a combination of seismic tomography and magnetotelluric measurements was used to create an image of the magma system beneath the surface. Magnetotelluric instruments measure electrical conductivity in the ground, which varies depending on the material beneath it. Since magma has a higher conductivity than solid rock, this technique is particularly useful around volcanoes.
Permanent monitoring networks of instruments help scientists piece together these images and gain a better understanding of Yellowstone’s magma system. The more detailed the map, the closer we can get to predicting how the system may behave over time, ensuring safety for those living nearby.
Source: https://www.usgs.gov/observatories/yvo/news/science-x-ray-vision-reveals-magma-beneath-yellowstone