Unconventional Seismic Monitoring in the Built Environment, From Canal Integrity to Coal Seam Fires

Date: 4/26/2019

Time: 04:00 PM

Room: Elliott Bay

Seismic approaches can be used in a wide variety of geotechnical applications, but the exact needs of any specific project defy any uniform methodology. With a bit of creativity, however, a diverse array of applications can be realized. Here, we present a few examples of unconventional uses of seismic data in anthropogenic environments. In a pilot study, we deployed a passive seismometer overnight at a highly active coal seam fire in Colorado. In addition to migrating elk, the instrument recorded intermittent, repeating impulsive events and distinct, unfamiliar long-period signals. We hypothesize that these signals are spalling of roof material or propagation of roof-subsidence fractures and air intake or slow flexure of the roof material, respectively. To test these hypotheses and to assess the utility of passive seismic monitoring of abandoned coal mine fires, a small array of six instruments has been deployed for a one-month trial. We will discuss the results of that monitoring. In a separate project, we were tasked with determining the location, geometry, and integrity of the wood-crib frame structure at a polluted, urban canal site. We used a horizontally polarized shear source to produce scattered Rayleigh and P wave responses on vertical-component geophones (finite-element simulations demonstrated that coupled S-Love-Rayleigh responses on horizontal components would be too complicated to use efficiently), which very clearly delineate the cross-beams and inner crib walls. Vertical sources elicit strong P and Rayleigh responses within the wood-crib itself, allowing for the determination of the full geometry of the frame and moduli and density of timbers and other geotechnical material.

Presenting Author: Will Levandowski

Authors