Fiber-seismic tomography

Abstract

A computer-implemented method useful for performing seismic tomography, including obtaining seismic data comprising distributed acoustic sensing (DAS) data, comprising at last one of P-wave or S-wave travel times from a plurality of seismic events to a plurality of recording stations coupled to a network of optical fibers in a geological structure; and generating tomography data from the DAS data, wherein tomography data is useful for characterizing the geological structure. We employ distributed acoustic sensing data recorded along a 100-km fiber-optic cable traversing the caldera to image its subsurface structure. Our images highlight a definite separation between the shallow hydrothermal system and the large magma chamber located at ~12 km depth. The combination of the geological evidence with our results shows how fluids exsolved through second boiling provide the source of the observed uplift and seismicity. Thus Fiber-seismic tomography reveals that the unrest in the Long Valley Caldera is likely driven by fluid from second boiling, not new magma intrusion.

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