3D survey details dangerous megathrust fault off Costa Rican coast

Feb. 12 (UPI) — Scientists have a better understanding of the dynamics of a dangerous megafault off the coast of Costa Rica, thanks to a new survey by researchers at the University of California, Santa Cruz.

The survey yielded detailed 3D images of the Costa Rican subduction zone, where the Cocos plate sinks and slides under the Caribbean plate.

Unlike similar megathrust faults, the Costa Rican fault features unusual earthquakes, patchy in their distribution. The ruptures rarely spread to shallow depths. Scientists believe the fault’s odd behavior is explained by its varied textures — corrugated patterns created by subduction activity.

“Our new imagery shows large variability in the conditions along the megathrust, which may be linked to a number of earthquake phenomena we observe in the region,” Joel Edwards, a doctoral candidate in Earth and planetary sciences at UC Santa Cruz, said in a news release.

Megathrust faults are capable of producing some of the largest earthquakes in the world. The seismic energy can also trigger tsunamis, threatening nearby coastal communities. Understanding the mechanics of megathrusts can help scientists more accurately estimate the risks facing local populations.

Scientists used advanced acoustic imaging technology to survey the corrugated ridges, or grooves, along the interface of the two plates. The patterns are similar to ridges found at the terminus of quickly receding glaciers.

The 3D images — detailed in the journal Nature Geoscience — revealed unique combinations of smooth expanses and textured ridges.

“This study produced an unprecedented view of the megathrust. Such 3D information is critical to our ability to better understand megathrust faults and associated hazards worldwide,” said Jared Kluesner, a geophysicist at the U.S. Geological Survey in Santa Cruz.

Scientists hope to learn more by drilling into the fault, but researchers had to conduct a 3D survey first before drilling at significant depths.

“At present, two drilling expeditions have been accomplished with shallower targets, and, though not yet scheduled, we are hopeful that the deep drilling will occur,” said Eli Silver, planetary sciences professor at UC Santa Cruz.