For more than a year, dozens of high-tech instruments sat on the floor of the Pacific Ocean. Placed there by a team of researchers from the 哔咔漫画 and Oregon State University, the devices collected data that is providing new insight into the mechanisms of earthquake generation.
The research, published this week in Nature Geoscience, outlines several seismic and aseismic events that preceded large earthquakes that occurred along the monitored fault off the coast of Oregon. Researchers say the data is helping provide context to the connection between these pre-earthquake events and the larger quakes themselves.
鈥淭his work shows what we believe is a relationship between episodic, aseismic slip events and large earthquakes that eventually occur on the outer shell of the Earth,鈥� said Jochen Braunmiller, PhD, a research assistant professor in USF鈥檚 School of Geosciences and a co-author of the study.
Aseismic slip describes movement along a fault that occurs without noticeable earthquake activity. According to Braunmiller, these aseismic events appear to work from the bottom-up and are associated with swarms of small earthquakes in the uppermost mantle of the Earth. Over time these events load the upper, crustal layer of the fault with tension before it ultimately slips and triggers an earthquake.
鈥淲e know there is this global tectonic plate motion occurring all the time. But we want to better understand how that movement effects earthquake nucleation,鈥� Braunmiller said. 鈥淓verything is driven by that plate movement, but how does that translate from the plate scale to these local seismic events at plate boundary faults 鈥� that鈥檚 what we looked at.鈥�
In this study, researchers deployed 55 ocean-bottom seismometers (OBS) along the Pacific Ocean鈥檚 Blanco Transform Fault, from 2012 to 2013. A transform fault is the boundary between two tectonic plates where the plate movement is primarily horizontal. Researchers say the Blanco Transform Fault is the ideal study site, given its propensity for seismic activity.
Over the length of the OBS deployment, the network of devices detected more than 1,600 earthquakes 鈥� providing researchers with the mountain of data used to make their findings. According to the study, recent technological advances in long-term OBS deployments made the work possible.
鈥淲hile this work was done by monitoring an ocean fault, the data has implications that go well beyond the ocean environment because it informs us about earthquake nucleation in a more general way,鈥� said Braunmiller. 鈥淚t provides really invaluable insight into how earthquakes are generated and how these faults work.鈥�