Seattle-Tacoma Urban Experiment
Help us understand amplification of shaking in our backyard by hosting a seismic station for a few weeks
Calling all Seattle-Tacoma area citizen scientists! The Pacific Northwest Seismic Network at UW and research partners from other departments and universities are conducting a slew of experiments right here in our backyard and need your help finding station hosts. Among the many science targets are imaging the Seattle, Tacoma and other local basins and understanding how much they may amplify shaking from a large earthquake as well as imaging the Seattle Fault zone.
Seattle and Tacoma both sit on top of large basins. Just like waves sloshing around in a bathtub back and forth, seismic waves can get trapped in a basin resulting in shaking much stronger than otherwise expected. Since we can't drill holes, fill them with dynamite, and set them off like in some oil field surveys, we have to rely on passive seismology methods. One way is to take advantage of all the seismic noise around us. Urban environments are very chatty when it comes to background seismic energy which gets generated from things like trucks, trains, machines and especially in bodies of water which beat on the bottom with increases and decreases in water pressure from waves at the surface. While none of these microsources are individually strong enough to record an ideal clear signal from the source to the receiving seismic station, collectively they can be used to simulate that ideal signal. We can do this by applying a technique called cross-correlation where we take records of noise from two stations at a time and slide them past each other with small offsets in time and compare their similarity. If you only compare a few minutes or hours of data, you get nothing, but when you do this with a few weeks of data, all of a sudden you can measure time lags of seismic waves and hence understand the subsurface between the two stations. The technique is called ambient noise cross-correlation or seismic interferometry (cool lecture: https://vimeo.com/93640104).
Hosts needn't worry about tiptoeing around their house or yard for two reasons. 1) Unless you're right next to the station, footsteps probably won't even register and 2) we are only looking at weeks long chunks of seismic background noise.
Indoor sites, about 3-6 weeks duration, flexible timing, Seattle-Tacoma area
Ideal sites are indoors and on concrete or on a thin layer of flooring (tile, linolium, etc) on top of concrete touching the ground, e.g. garages, basements, storage closets, warehouses etc. The instrument package is about as big as a cooler and uses less power than a small night light. We are looking for sites in the Seattle and Tacoma and surrounding areas, basically anything not grey in the map. We only have a limited number of instruments that can go out at any one time, so it might be a while before we get to your city/region. We are flexible with our timing for installs & pick-ups. Install usually takes about an hour, pick up takes about 30 minutes.
Backyard sites, 4 weeks from mid July - mid August, Central District to Mt. Baker/Beacon Hill:
This is an exciting project that will take a high resolution zoomed in look at one part of the Seattle basin around the Seattle Fault zone using over 100 stations from mid July to mid August. These small coffee-can sized stations work best being plopped down in backyards. We're hoping to have a station about every 100 yards (about every 3 to 4 houses), so ask your neighbors to join! Install and pick-up take less than 10 minutes.