CAREER:Potential of fiber acoustic sensing in the next-generation seismic networks

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Scientists use large networks of seismic sensors to detect ground vibrations caused by earthquakes, in order to understand their physics and help mitigate related hazard. In regions with high seismic activity, such as California, there are dense networks with one seismic sensor every 10 to 30 km. However, past large earthquakes taught us that this station density is still not enough. Earthquake shaking can change dramatically from block to block, due to highly complex shallow soil structures. Furthermore, many small earthquakes are not detected by the current seismic networks, smearing our images of faults. With denser seismic networks, scientists will be able to better map earthquake faults and monitor their activities, also to provide more clear pictures of Earth interior.Distributed acoustic sensing (DAS) is an emerging technology that converts every meter of a long optical fiber to a seismic sensor, by shining a laser pulse into the fiber from one end and interrogating the "echo" scattered from fiber defects. DAS provides a scalable and affordable way to deploy a dense seismic network. This CAREER project will build the Pasadena Array, the first continuous city-scale fiber seismic network, to explore the potential of DAS in the next-generation seismic networks. The researcher will collaborate with the City of Pasadena to transform an existing telecommunication fiber network owned by the city to a seismic array with 50,000 sensors within 10km. The Pasadena Array will be a unique platform to test and characterize different generations of DAS instruments, develop data processing algorithms, and explore applications in seismology. The orders of magnitude increase in station density will push the limits of earthquake detection, basin structure imaging, and hazard assessment/mitigation. Ultimately, the Pasadena Array will serve as a template to build a million-sensor seismic network in Southern California, and transform how we design, build, and use seismic networks nationally and globally.The Broader Impacts of the project include the benefits enhanced knowledge of the impacts of earthquakes and the involvement of students in the Pasadena school system in better understanding seismic hazards.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.