A Scientist's Life: Kerry Key

Scripps geophysicist describes using electromagnetics to see under the ocean

Kerry Key, a geophysicist at the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics at Scripps Institution of Oceanography, discovered a passion for geology as a student at Palomar Community College in San Marcos, Calif. He then attended UC San Diego, where he received a bachelor’s degree in earth sciences and a PhD degree in geophysics. He is now a faculty member at Scripps. Key was recently honored as Palomar College’s 2014 Alumnus of the Year.

explorations now: Describe what you do for a living.

Kerry Key: I’m a marine geophysicist, which means I use remote sensing methods to study the geologic structure below the seafloor. In order to study the sub-seafloor in areas deeper than can be reached by a drilling rig, you have to use remote sensing methods that measure how some form of energy travels through the ground. For example much of what we know about the geologic structure of the deep crust, mantle and core is known from mapping how seismic energy travels through our planet.

My particular research uses electromagnetic wave energy and is a more recently developed approach to studying Earth. We map how electromagnetic waves travel through the seabed and that tells us about the geologic structure and the fluids that are in these sediments and rocks. For example, we use electromagnetic waves to make maps of where there is magma at seafloor volcanoes, where water is present along fault zones and fractures in the seafloor, and we also use them for making maps of where there’s oil and gas buried in the sediments on the continental shelves.

en: How did you select this field as a career?

KK: Few people grow up knowing that geophysics even exists. It’s one of those shadow fields that most people don’t really discover until they are taking a class in college because they were interested in geology and then all of a sudden they learn that there’s geophysics, which uses physics to study the structure of the earth.

At the end of high school my main goals in life were to continue hanging out with my friends playing music and riding our skateboards, so I didn’t even apply to any universities. However, in hindsight I was really fortunate that my parents convinced me to at least try attending Palomar Community College. While I was there I took nearly every class they offered that ends with “ology” such as archaeology, anthropology, biology, ecology, meteorology and zoology. That was how I discovered geology and a love for doing science outdoors. From there I transferred to the earth sciences program at UC San Diego and got my bachelor’s degree in 1998.

I liked studying geology and learning about the structure of the earth. One course in particular, field geophysics, was really an eye-opener since in the classroom we learned, for example, the theories for gravity and geomagnetic exploration methods, and then we went out with a gravimeter and magnetometer and we collected real-world gravity and magnetic measurements around San Diego. Then we had to interpret those data using theories we’d learned.

So it was really neat to tie in theory with practice. And that’s pretty much what I do today. I use theory to write electromagnetic modeling and simulation codes and then we go out and collect data using research ships. Then we get to go back to our offices and spend the next year or more analyzing the data and writing papers about what the data tell us about the seafloor geology.

en: Why was Scripps the best option for this field?

KK: The field of using electromagnetic waves to study the seafloor was pioneered here at Scripps starting in the 1960s with Professor Charles “Chip” Cox and Jean Filloux. A lot of the methods that we use today employ engineering and design principles that were established by them.

My PhD advisor Steve Constable came to Scripps in the 1980s as a postdoctoral researcher and learned a lot working in Chip’s lab. Then I learned from Steve. Now I have my own students and I hope that I’m teaching them how they can become the future leaders in this field.

Scripps is the best option because there are only a few universities in the world that are doing marine electromagnetic research and Scripps has the largest and most capable instrumentation fleet in the academic world. This technology is also being used by industry for oil and gas exploration on the continental shelves.

en: What are some of the major questions in your field?

KK: One major question in this field is understanding what exactly the asthenosphere is. The earth is composed of tectonic plates, which are the rigid plates on the outer shell of the earth, and we know that they slide over the mantle. The zone that accommodates that sliding, in between the plates and the mantle, is known as the asthenosphere.

There are primarily two camps, one that thinks the asthenosphere is partially molten while another camp thinks that it’s not molten, but has very low viscosity, which means that it’s not rigid and can flow if enough force is applied to it. We’ve collected some data that suggest that the asthenosphere is partially molten but other scientists have collected data saying that it’s not partially molten. So this is an outstanding question that we are hoping to answer in the next few years.

Another big question in my field concerns subduction zones that trigger large tsunami-generating earthquakes and understanding why that happens for some earthquakes and not others. It may have to do with how much water is present along the plate interface. In a subduction zone, the oceanic plate is diving down beneath the continental plate and the interface is where the plates grind past each other. The amount of water that’s present in that interface is going to govern the friction and how well those two plates can slide past each other.

The amount of water being subducted potentially has implications for generating tsunamis. If an earthquake rupture can propagate from deep down beneath the seafloor all the way up along the plate interface, and if it moves that seafloor enough, it could generate a tsunami.

en: What are some of the tools and methods used in your research?

KK: In order to collect data on electromagnetic waves traveling through the earth, we need a source of energy and a receiver to measure that energy. Some of the research that I’m involved in uses a controlled-source transmitter as the source. That’s basically a giant dipole antenna that we deep-tow behind one of our ships using a really long cable.

The towing cable is about six or seven kilometers (3.7 to 4.3 miles) long and is attached to a winch on the ship, which allows us to lower the transmitter down all the way to the seafloor. We tow the transmitter right above the seabed and it emits electromagnetic waves.

Then we put out an array of receivers that are about the size of a small washing machine, except they have four long arms on them that sense the electric and magnetic fields on the seafloor, and they have a computer inside that records how these fields change in strength and polarity.

We put out anywhere between 40 to 60 receivers on the seabed, and then we tow our transmitter on a grid pattern through the array of receivers and we map how the electromagnetic waves travel through the seabed. By knowing how well they travel through the seabed, we can make inferences on what the geologic structure is.

en: How does your research impact the broad public?

KK: There are many different ways that this research can relate to people. A lot of the research that I’m involved in is looking at geohazards, such as volcanoes on the seafloor and fault zones that are located close to continental margins.

When we put sensors down on the seabed, we are trying to understand the details of these structures – what sorts of fluids are in the fault zones, or how much magma is in the source region for seafloor volcanoes. There is a lot that we still don’t know about basic components of seafloor geology and plate tectonics, and we have to go out there and collect these data sets so that we can better understand them.

Other parts of our research involve finding better ways to explore for hydrocarbon energy reserves trapped beneath the seafloor.  In fact, most of our funding comes from the exploration industry, which has provided support that allowed our group to build up a large fleet of instruments and create the computer tools to process and analyze our data. I feel really fortunate that we’re then able to use these tools along with funding support from the National Science Foundation to go out and explore basic science questions about offshore fault zones, seafloor volcanoes, and the structure of the crust and mantle.

In fact, just recently we studied a fault zone offshore of Oregon and Washington to understand how fluids lubricate the faults and can potentially enhance large earthquakes and tsunamis.

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