SPOKANE, Wash. — Starting Friday, scientists will be using sound waves to look down into the Earth, and the result will be a picture of the geology beneath Spokane, perhaps including faults that cause shallow earthquakes. The study will help scientists better understand earthquake hazards in the Spokane area. Results of the assessment will be shared with Washington State Emergency Management and local emergency managers for planning purposes.
USGS scientists will be using a vibrating trailer to send low-amplitude sound waves into the ground, and an array of 240 seismometers to record the returning echoes. Computer processing of the recordings will produce a picture of the Earth that is similar to sonograms used in medical imaging. The images of the Earth, however, will extend to nearly a mile depth.
During the field work, expected to last 3 days, the public will see a crew of 7 people working along the side of E. Baldwin and W. Shannon Avenues, accompanied by a large heavy trailer with two white water tanks on the back towed behind a pickup truck, and 2 additional support trucks. The trailer creates vibrations that penetrate below the ground surface, and the reflected echoes of the vibrations are recorded by a long string of sensors stretching out about a half mile from the trailer. The harmless vibrations are not strong enough to be felt except by those standing near the trailer, and will not cause any damage to the roadbed or other structures. The trailer will produce vibrations for about 20-30 seconds in one location, and then move about 15 feet down the road to repeat the process. The survey will cover approximately one half mile per day, moving east to west along the side of the road.
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