FLATS array

My main PhD project used the FLATS (Fault Locations and Active Tectonics from Seismicity) array. The array consists of 13 seismometers (purple triangles) which I helped deploy and maintain from 2014–2019. It observed large ground motion from the underlying Nenana Basin (color gradient) caused by earthquakes from 2 NE strike-slip faults (black lines with white outline).

The ground motion is also influenced by the local Tanana River, atmospheric effects and amplification from the sedimentary basin.

Map courtesy of Doyon Ltd.

Environmental Seismology

Many seismometers were near the river and we can see how river discharge is related to ground motion.

Wind speed influences seismic noise across all wavelengths (frequencies) in our analysis

Anthroprogenic Noise

Every September, moose hunting season begins in Minto Flats. A seismometer near a hunter's campground can detect activity by examining high frequency (10 Hz) signals.

Seismic noise is complicated

Seismic noise can be influenced by river, wind and elastic properties of the earth. River stage height and wind vary with time. During summer, river stage height is highest and it causes high frequency (~10 Hz) signals to increase for stations close to the river (unbolded lines). During winter, storms in the northern Pacific Ocean causes an increase in noise levels for 0.05–0.25 Hz. Seismic stations placed on bedrock (Magenta and Cyan) record significantly smaller noise levels than stations on sedimentary basins for 0.1–3 Hz. The difference between seismic noise in sedimentary basins vs bedrock (Bottom) is 14 dB and is time invariant for 0.1–3 Hz. Further investigation is needed to pinpoint the mechanism responsible for amplification at 20 Hz.

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