By Wes Saylors
Dr. Scott Marshall, a geophysicist in Appalachian State University’s Department of Geology, finds earthquakes fascinating. Marshall is interested in knowing what’s below the observable surface.
“That’s one of the fundamental tenants of geophysics: learning how to image the subsurface,” said Marshall. “If you can see the rocks, you hire a geologist. If you can’t see the rocks, you hire a geophysicist.”
Marshall recently received additional funding from The University of Southern California’s Southern California Earthquake Center (SCEC) for advanced geodetic imaging of deformation rates throughout the Ventura Special Fault Study Area Region. In other words, Marshall uses satellite images to map where faults are and how fast they are moving. He has been funded consecutively since 2013, for a total of $87,000.
Satellite data can help map fault lines in the subsurface of Southern California. In response to the often-asked question, “Is Los Angeles going to eventually fall into the ocean?” Marshall instead revealed something more incredible. “Los Angeles,” he said, “is headed northwest.” Pointing to evidence on his computer screen, he showed the incremental movement of the Los Angeles region northwestward. “If it keeps going like this for millions of years, it’ll brush up against San Francisco.”
This information comes courtesy of satellite data received from space – Global Positioning System (GPS) data. “The same network of satellites that most people use to find the best coffee in town can also be used to map out earthquakes and faults,” quips Marshall.
“This is an exciting time to be a geophysicist,” Marshall said. “There is now satellite-based technology that allows you to see things not possible just 10 years ago. We can measure a millimeter of movement per year from space – accurately.”
Marshall’s research “tries to predict where faults are and how fast they are moving.” This data helps California with building codes, determining which areas are most at risk from earthquakes, and which buildings will need to be retrofitted in order to have a chance to survive an earthquake.
With the data Marshall accumulates, regions like southern California can use the information to make events like these as survivable as possible.
As Marshall pointed out, earthquakes alone do not kill people. Much of the damage is done by collapsing buildings and houses. The sort of structure you are in when a quake happens is far more important than your proximity to a fault line.
Modern satellite technology has allowed Marshall to “put the puzzle together to see how things work. I write computer code that solves mathematical geophysical equations related to fault motions. The model predictions can then be directly compared to the satellite measurements.”
While Marshall’s primary area of study is southern California, he points out faults are everywhere. “The entire eastern U.S. region experiences about 300-400 earthquakes per year. Most are not felt. In southern California, alone (a much smaller region), they experience about 16,000 events per year. This is because California lies at a tectonic plate boundary where two plates are actively sliding past each other.”
He summed up, “Earthquakes are fascinating. I find them fascinating.”
“The same network of satellites that most people use to find the best coffee in town can also be used to map out earthquakes and faults.”
– Dr. Scott Marshall, geophysicist