9 January 2025—Earthquakes may be the noisy, attention-getters of seismological research, but geophysicist Daniel Gittins is focused on something a bit quieter.
“Creep is the slow, gradual movement along faults that happens without causing an earthquake. Unlike sudden earthquakes, which release a lot of energy, aseismic creep occurs smoothly and quietly over time,” explains Gittins, a visiting postdoctoral fellow at CIRES at the University of Colorado, Boulder. “Although bursts of creep can occur, these are often slipping at speeds more comparable to the growth rate of fingernails—10-5 meters per second—than the slip speeds we observe in earthquakes, which are closer to a meter per second or a leisurely walk on flat ground.”
Gittins and his colleagues study aseismic creep to better understand the underlying mechanics of fault movement and the role creep might play in the nucleation of earthquakes and in stress transfer, he notes.
“Aseismic slip has been observed to affect the ability of earthquakes to propagate into certain regions of faults, notably the barrier to rupture that the creeping section of the San Andreas Fault appears to be,” Gittins says, “preventing both the magnitude 7.9 1906 San Francisco or magnitude 7.9 1856 Fort Tejon earthquakes from entering this region.”
Seismic hazard assessment relies on both aseismic and seismic movement, he adds. “A lot of times, infrastructure has to cross faults and understanding the afterslip of earthquakes and how that affects fault-crossing infrastructure such as roads and pipelines is also important.”
Gittins’ research focuses on creep at faults in Central and Southern California, Pakistan and Turkiyë, but aseismic creep is a “worldwide phenomenon,” he notes, taking place in subduction zones and strike-slip faults from Japan to Trinidad & Tobago.
The tools of choice for studying creep are the aptly named creepmeters, which measure displacement across a fault at an oblique angle, at depths ranging from centimeters to meters.
A creepmeter “is anchored on both sides of the fault, and as the fault moves, it causes the two anchor points or piers to move further away from one another. This displacement is measured by a hall-effect rotary sensor that rotates as the wire wrapped around it is pulled by the displacement of the two piers away from one another,” Gittins explains. “This rotation changes the voltage the sensor measures, which we can then convert to displacement using a calibration calculation in the lab.”
Gittins says his lab “is more like a workshop,” where he designs, creates and assembles creepmeters. His work includes every part of the process, starting with CAD software to design creepmeter parts and using a 3D printer to create the parts, all the way through to soldering the electronics and calibrating the finished creepmeter.
His fieldwork mostly involves installing these instruments in thin excavated trenches and performing their maintenance. “Field installations are often some of the more difficult parts of my day-to-day work. They often involve working in challenging conditions, be it hot and dry in the Salton Trough or at high altitudes in the Colorado mountains,” Gittins says.
One of Gittins’ other main projects is coding in Python to create standardized data pipelines from raw creep data that can be used by other researchers. “My most recent of these projects is examining over 75 creepmeters from across the world to produce a comprehensive catalog of creep events, akin to an earthquake catalog used so widely in seismology,” he says.
“If money and time were no object, I would like to install a dense array of creepmeters, borehole strainmeters and [distributed acoustic sensing] DAS across the creeping section of the San Andreas Fault to fully characterize the strain field during the deformation caused by creep events,” Gittins says. “These instruments would be installed at various depths and distances away from the fault to understand how the approaching dislocation moves with time on the fault plane and would allow us to work out the mechanics of how these events form and propagate.”
Gittins has been interested in geology since he was a child hunting fossils on the beaches in Yorkshire in the U.K., “marveling at the cliff falls that would bring ironstone and ammonite nodules down to the beach below and wondering about how these things even got into the ground anyway. That’s likely when my desire to be a scientist began. I probably drove my parents mad with how often I would ask why this happened.”
His interests in seismology were sparked by images from the 2004 Sumatra and 2011 Tohoku earthquakes.
“I wanted to get into a career in seismology to better understand natural hazards from a fundamental physics point of view, following that childlike curiosity for how things work, but also to be able to understand them to provide some insight and understanding that might be able to help communities better prepare people for the impacts of earthquakes,” says Gittins.
Workshops, conferences and collaborations have all helped Gittins grow and become more confident as a researcher, he says. Learning how to explain his work at in-person conferences, after so many online collaborations during the COVID-19 pandemic, was especially important.
“Not many people work with creepmeter data, and I spent a lot of time at conferences explaining what exactly they were and how their data can be used, so explaining your science in plain English to non-experts is a skill that I recommend to people,” he says. “This is particularly important as, in your career, you may have to work with stakeholders that are non-experts on projects, and because it is important to be able to disseminate science to the general public in a way they can understand, especially if it relates to something such as seismic hazard in the region where they live.”
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