Slow Earthquakes in the Pacific Northwest
Installation of Sequim Tiltmeter
The final Cascadia Tiltmeter was completed in September of 2006 in the vicinity of Sequim, WA. Winnie Sallee of the Sequim Valley Airport made construction possible by allowing use of airport property.
This tiltmeter consists of two arms approximaely at right angles, in an L-shape plan view with the corner vault in SE end. The south and east sensors share a solid pier monument and the system is run by AC power. Manholes were constructed in concrete with soil completely covering the lids to minimize temperature vairation. Electronics are housed in exterior boxes. The float system was changed for this newset system and relies on surface tension rather than bouyancy. While this feature aided in damping the oscillitory resonances it also allowed failure when surface tension was compromised. New 4-bulb float systems have been employed with LVDT housed within the reservoir itself to correct this error.
Data stored in the computer are accessed via cell-phone through the internet. Power to the tiltmeter comes through an AC hookup (120V at 0.2 Amp is equivalent to a 25W light bulb).