Seismic Velocity Estimation Using Passive Downhole Distributed Acoustic Sensing Records: Examples From the San Andreas Fault Observatory at Depth

Structural imaging and event location require an accurate estimation of the seismic velocity. However, active seismic surveys used to estimate it are expensive and time‐consuming. During the last decade, fiber‐optic‐based distributed acoustic sensing has emerged as a reliable, enduring, and high‐resolution seismic sensing technology. We show how downhole distributed acoustic sensing passive records from the San Andreas Fault Observatory at Depth can be used for seismic velocity estimation. Using data recorded from earthquakes propagating near‐vertically, we compute seismic velocities using first‐break picking as well as slant stack decomposition. This methodology allows for the estimation of both P and S wave velocity models. We also use records of the ambient seismic field for interferometry and Pwave velocity model extraction. Results are compared to a regional model obtained from surface seismic as well as a conventional downhole geophone survey. We find that using recorded earthquakes, we obtain the highest P wave model resolution. In addition, it is the only method that allows for S wave velocity estimation. Computed P and S models unravel three distinct areas at the depth range of 50‐750 m, which were not present in the regional model. In addition, we find high VP/VS values near the surface and a possible VP/VS anomaly about 500 m deep. We confirm its existence by observing a strong S‐P mode conversion at that depth.

[1]  Roel Snieder,et al.  Application of seismic interferometry to extract P- and S-wave propagation and observation of shear-wave splitting from noise data at Cold Lake, Alberta, Canada , 2008 .

[2]  Mark D. Zoback,et al.  Scientific Drilling Into the San Andreas Fault Zone —An Overview of SAFOD's First Five Years , 2011 .

[3]  H. Paulssen,et al.  P and S Velocity Structure in the Groningen Gas Reservoir From Noise Interferometry , 2017 .

[4]  D. Schmitt,et al.  First-break timing: Arrival onset times by direct correlation , 1999 .

[5]  E. Blias.  Stacking velocities in the presence of overburden velocity anomalies , 2009 .

[6]  James P. Evans,et al.  Mineralogic and Textural Analyses of Drill Cuttings from the San Andreas Fault Observatory at Depth (SAFOD) Boreholes: Initial Interpretations of Fault Zone Composition and Constraints on Geologic Models , 2007 .

[7]  M. Reshef,et al.  Velocity analysis and subsurface source location improvement using moveout-corrected gathers , 2019, GEOPHYSICS.

[8]  Wilfred Berlang,et al.  Distributed acoustic sensing for reservoir monitoring with vertical seismic profiling , 2014 .

[9]  Tom Richard Parker,et al.  Distributed Acoustic Sensing – a new tool for seismic applications , 2014 .

[10]  B. Biondi,et al.  Earthquakes analysis using data recorded by the Stanford DAS array , 2017 .

[11]  T. Daley,et al.  Field testing of modular borehole monitoring with simultaneous distributed acoustic sensing and geophone vertical seismic profiles at Citronelle, Alabama , 2016 .

[12]  Gregory C. Beroza,et al.  Distributed acoustic sensing for seismic monitoring in challenging environments , 2020 .

[13]  I. Silvestrov,et al.  Smart DAS upholes for simultaneous land near-surface characterization and subsurface imaging , 2017 .

[14]  M. Karrenbach,et al.  Hydraulic-fracturing-induced strain and microseismic using in situ distributed fiber-optic sensing , 2017 .

[15]  Yingjie Yang,et al.  Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements , 2007 .

[16]  Arthur H. Hartog,et al.  The effect of gauge length on axially incident P‐waves measured using fibre optic distributed vibration sensing , 2017 .

[17]  Andrey Bakulin,et al.  The virtual source method: Theory and case study , 2006 .

[18]  B. T. Meggitt,et al.  Optical Fiber Sensor Technology Fundamentals , 2000 .

[19]  N. Nakata,et al.  Site characterization at Groningen gas field area through joint surface-borehole H/V analysis , 2018 .

[20]  Dante Fratta,et al.  Properties of Noise Cross‐Correlation Functions Obtained from a Distributed Acoustic Sensing Array at Garner Valley, California , 2015 .

[21]  Arthur H. Hartog,et al.  A study of the geophysical response of distributed fibre optic acoustic sensors through laboratory‐scale experiments , 2016 .

[22]  P. Jousset,et al.  Dynamic strain determination using fibre-optic cables allows imaging of seismological and structural features , 2018, Nature Communications.

[23]  Florian Bleibinhaus,et al.  Structure of the San Andreas fault zone at SAFOD from a seismic refraction survey , 2006 .

[24]  Wilfred Berlang,et al.  Distributed acoustic sensing for reservoir monitoring with VSP , 2013 .

[25]  Eileen R. Martin,et al.  Fiber‐Optic Network Observations of Earthquake Wavefields , 2017 .

[26]  Arthur H. Hartog,et al.  A study of the geophysical response of distributed fibre optic acoustic sensors through laboratory-scale experiments: Geophysical response of fibre optic sensors , 2017 .

[27]  Robert G. Clapp,et al.  Seismic monitoring leveraging existing telecom infrastructure at the SDASA: Active, passive, and ambient-noise analysis , 2017 .

[28]  Clement Kostov,et al.  High-resolution velocity spectra using eigenstructure methods , 1989 .

[29]  Michel Campillo,et al.  Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise , 2004 .

[30]  Douglas E. Miller,et al.  Field testing of fiber-optic distributed acoustic sensing (DAS) for subsurface seismic monitoring , 2013 .

[31]  P. Connolly,et al.  Removal of overburden velocity anomaly effects for depth conversion , 1999 .

[32]  M. Taner,et al.  SEMBLANCE AND OTHER COHERENCY MEASURES FOR MULTICHANNEL DATA , 1971 .

[33]  Roel Snieder,et al.  Estimating near‐surface shear wave velocities in Japan by applying seismic interferometry to KiK‐net data , 2012 .

[34]  Martin Landrø,et al.  Repeatability issues of 3-D VSP data , 1999 .

[35]  J. Ajo-Franklin,et al.  Introduction to Interferometry of Fiber Optic Strain Measurements , 2018 .

[36]  F. Waldhauser,et al.  A Double-Difference Earthquake Location Algorithm: Method and Application to the Northern Hayward Fault, California , 2000 .

[37]  B. Hardage.  Vertical seismic profiling : principles , 1984 .

[38]  Dante Fratta,et al.  Ground motion response to an ML 4.3 earthquake using co-located distributed acoustic sensing and seismometer arrays , 2018 .

[39]  Karen N⊘rgaard Madsen,et al.  Data-driven depth calibration for distributed acoustic sensing , 2016 .

[40]  S. Nooner,et al.  Recording Earth Strain With Optical Fibers , 2008, IEEE Sensors Journal.

[41]  Barry Freifeld,et al.  Distributed Acoustic Sensing for Seismic Monitoring of The Near Surface: A Traffic-Noise Interferometry Case Study , 2017, Scientific Reports.

[42]  B. Biondi.  Velocity estimation by beam stack , 1992 .

[44]  J. C. Hornman.  Field trial of seismic recording using distributed acoustic sensing with broadside sensitive fibre‐optic cables , 2017 .

[45]  Florian Bleibinhaus,et al.  Structure of the California Coast Ranges and San Andreas Fault at SAFOD from seismic waveform inversion and reflection imaging , 2007 .

[46]  K. Wapenaar,et al.  Green's function representations for seismic interferometry , 2006 .