Tara Nye

What's Shaking? Geologic effects on Seismic Hazard

Tara Nye received her bachelor's degree in geology from BYU before going on to Oregon State to receive her PhD. She specializes in seismology and came to BYU on February 12th to teach students about her ongoing research on seismic hazards.

Dr. Nye calculates seismic hazards by creating ground-motion models, which take in information about nearby faults where earthquakes could originate, as well as expected magnitudes, the distance to potential earthquakes, and the potential shaking at the site. The shaking intensity in this equation is heavily reliant on the geologic properties of the site. As the quake spreads through soft ground, its waves slow down as the amplitude increases. While small buildings and houses are susceptible to high-frequency, low-amplitude waves, larger buildings are more likely to fail when hit with low-frequency, high-amplitude waves. Thus, it is essential to know the characteristics of the surface rock at a site to establish building codes and limit damage.

In Dr. Nye's research, she noticed some sites where the data didn't quite match up with the expected predictions. She decided to research what effects an earthquake's path has on a seismic hazard. Her data was taken from 823 seismic stations in the San Francisco Bay area, looking at 1129 seismic events between a magnitude of three and six, giving her around 72,000 records to analyze. While most predictions rely solely on the Vs30, the velocity of waves in the upper 30 meters of crust, Dr. Nye also examined samples from deeper in the crust to try and measure the waves' path. Her objective was to search for definable crustal properties along the earthquake-to-site path.

Dr. Nye already knew that sedimentary basins affect the shaking intensity at a site, but she wondered if they also affected the path. Would passing through the basin impact not only the shaking within the basin but also beyond it? Next, she wanted to look at how passing through fault zones—the broken-up and damaged area around a fault line—would impact the waves. In both cases she found interesting results. Sedimentary basins amplify the waves, and passing through fault zones causes more attenuation. The more misaligned the fault zone or the more faults the wave travels through, the more attenuation.

Though still a work in progress, Dr. Nye's research is helping us better understand and prepare for earthquakes. She hopes to further our knowledge of seismic activity and help prevent catastrophe around the globe, improving the lives of countless millions.