Scientists To Map Earthquake Zones Study Will Explore Bottom Of Puget Sound For Hazards

U.S. and Canadian scientists will sail Puget Sound and Georgia Strait next year and bombard the sea floor with bursts of compressed air to try to map the hazards of shallow earthquakes in the region.

The study is known by its acronym SHIPS, for Seismic Hazards Investigations in Puget Sound, was outlined at a news conference.

Much like a doctor using ultra-sound to scan the human body, the researchers will use an array of marine air guns to fire charges of compressed air into the water to produce sonic maps. Data from the artificially produced sound waves that travel through deep rock layers will be recorded on the surface by sensitive instruments.

Scientists hope the data will help them map faults capable of producing major quakes and estimate where the greatest shaking might occur.

“The goal of SHIPS is NOT earthquake prediction,” said lead researcher Mike Fisher of the U.S. Geological Survey. “Instead, SHIPS is going to focus on earthquake processes.”

He said the information should help city planners in updating building codes and preparing emergency-response plans.

“The large earthquakes that we know to have occurred along the Pacific Coast in the past have ignored political boundaries,” Roy Hyndman, a geophysicist with the Canadian Geological Survey, added in a statement. “When the next large earthquake occurs, it too will not discriminate along national borders, so it is in all our interests to work together on this project.”

The Canadian research ship, Tully, and the University of Washington vessel, Thomas Thompson, will cruise the Puget Sound from Olympia northward into Georgia Strait and then westward through the Strait of Juan De Fuca. The two-week cruise is scheduled for next March.

Large quakes occur along the Pacific Coast because rocks under the Pacific Ocean are thrust eastward beneath the North American continent, in a process called subduction.

There is geological evidence of three types of quakes in the region: massive, magnitude 9 subduction quakes, caused by contact between the bottom of the continent and the top of the shifting ocean rocks; deep quakes of magnitude 6.5 to 7.5 beneath central Puget Sound, where the shifting ocean rocks push beneath the North American continent; and shallow quakes from faults just beneath land.