Continuous seismic monitoring can be a crucial tool to provide early warning of potentially hazardous conditions developing in the subsurface, as well as monitoring the flow of natural resources such as water and hydrocarbons. However, the cost of continuous monitoring is a significant obstacle to its widespread application. Distributed Acoustic Sensors (DAS) arrays have the potential of enabling cost-effective continuous and spatially dense seismic monitoring over large areas. By leveraging the preexisting fiber infrastructure deployed for telecommunication purposes, we could build large seismic arrays under densely populated cities around the world.
Starting the beginning of September 2016, we have been continuously recording seismic data as sensed by a fiber-optic cable placed under Stanford University campus and measured by an OptaSense DAS system. Our “Stanford Fiber Seismic Observatory (S-FSO)” experiment aims at studying the feasibility of using a DAS array that record data using a fiber-optic cable “free-floating” in a PVC conduit buried in the ground. Our array has recorded hundreds of seismic events. Analysis of these events shows that the signal is highly repeatable and correlates well with the data recorded by a broadband seismometer located on campus. Furthermore, by analyzing the S-FSO data we have identified a few weak local events that were not catalogued in the USGS on-line earthquake catalogue. We are also using ambient (mostly anthropogenic) noise interferometry to estimate and monitor subsurface properties under the array. Data analysis has prompted us to develop new theoretical models of the data recorded by the fiber to better understand the recorded signal and the interferometric data.
Speaker: Biondo Biondi, Stanford
Contact:Website: Click to Visit
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