What changes when we use ambient noise recorded by fiber optics?

Eileen Martin1,2, Nate Lindsey3,2, Biondo Biondi3, Jonathan Ajo-Franklin4,2, Tieyuan Zhu5

1. Virginia Tech 2. Lawrence Berkley Lab 3. Stanford University 4. Rice University 5. Pennsylvania State University

1© authors. All rights reserved.

Part 1: If an array passively records a particular source, how should it look on different parts of the array?

Part 2: For any pair of receivers in the array, what should their cross-correlations look like?

Examples of Passively Recording Fiber Optic Arrays

Richmond Field Station (LBL/CRREL)

Fairbanks Permafrost Thaw Study (LBL/CRREL)

Stanford Fiber Optic Seismic Observatory

Penn State FORESEE Array

2

DAS Records Fiber’s Axial Component of Strain Tensor

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Longitudinal:P-waves, Rayleigh waves

Transverse: S-waves, Love waves

Geophone/Seismometer:

3

DAS = Distributed Acoustic Sensing

Detected Signal Comparison

Note: Sensors oriented along 0 degrees

Rayleigh and Love Waves

4

Detected Signal Comparison: Gauge Effect

Note: Sensors oriented along 0 degrees

Rayleigh and Love Waves

5

if wavelength too small relative to

gauge length

Detected Signal Comparison P, SV and SH Waves

Note: Sensors oriented along 0

degrees horizontal

Wave’s vertical angle of incidence 22.5 degrees

6

Note: Sensors oriented along 0

degrees horizontal

Wave’s vertical angle of incidence 45 degrees

Detected Signal Comparison P, SV and SH Waves

7

Note: Sensors oriented along 0

degrees horizontal

Wave’s vertical angle of incidence 67.5 degrees

Detected Signal Comparison P, SV and SH Waves

8

Nearby Earthquake ExampleMagnitude 3.5 earthquake

Piedmont, CA Recorded on the Stanford Fiber Optic Seismic Observatory

9

S-wave Polarity Switches at Corners

10

Radial-Radial Cross-correlation SensitivityRayleigh and Love Waves

11

Simple Synthetic: Random Sources Around Sensorsbased on Wapenaar et al, 2010

2000 m/s velocity

1200 m

Sources randomly in 2000-3000 m radius

12

Simple Synthetic: Random Sources Around Sensorsbased on Wapenaar et al, 2010

2000 m/s velocity

records fiber 2records fiber 1

13

Simple Synthetic: Random Sources Around Sensorsbased on Wapenaar et al, 2010

2000 m/s velocity 14

Simple Synthetic: Random Sources Around Sensorsbased on Wapenaar et al, 2010

2000 m/s velocityFiber, geophone

15

Radial-Radial Cross-correlation SensitivityRayleigh and Love Waves

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Transverse-Transverse Cross-correlation SensitivityRayleigh and Love Waves

17

Simple Synthetic: Random Love Wave Sources Around Sensors

based on Wapenaar et al, 2010

2000 m/s velocityFiber, geophone

Love wave sources only

18

Simple Synthetic: Random Sources Around Sensorsbased on Wapenaar et al, 2010

2000 m/s velocityFiber, geophone

Love and Rayleigh Sources

19

E.R. Martin and B.L. Biondi, “Ambient noise interferometry across two-dimensional DAS arrays,” 2017, SEG Ann. Mtg. Expanded Abstracts, 2642-2646.

20

How this affects real data: we get signals along Parallel lines, but not at the closest offsets

Effects at Fairbanks Thaw Testslide ℅ Nate Lindsey

Strong

Strong

Weak

Strong

StrongWeak

Strong

Strong

Weak

21Lindsey et al., 2018 Fall AGU Meeting

Most (not all) parallel channel pairs are useful

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pairs that should be excluded

(425.0, 425.0)(-425.0, 425.0)

(-425.0, -850.0)

More orthogonal channel pairs are useful

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pairs that should be excluded

Ackn

owle

dgem

ents

24

Instrumentation used for data acquisition:OptaSense (Standford Fiber Optic Seismic Observatory)Silixa (Penn State FORESEE, Fairbanks Permafrost, Richmond Field Station)

Support for Stanford Fiber Optic Seismic Observatory:Stanford Exploration Project AffiliatesSchlumberger Innovation FellowshipDOE Computational Science Graduate Fellowship DE-FG02-97ER25308

Support for Penn State FORESEE Array:Seed grant from Penn State Institutes of Energy and the EnvironmentCollaborators: Patrick Fox, Andy Nyblade, David StensrudPenn State ITVirginia Tech Advanced Research Computing

Support for Richmond Field Station and Fairbanks Permafrost Experiments:SERDP Grant number RC-2437Many collaborators led by PI Jonathan Ajo-Franklin and Co-PI Anna Wagner

Reference: E Martin, N Lindsey, J Ajo-Franklin, B Biondi, “Introduction to Interferometry of Fiber Optic Strain Measurements,”Preprint on EarthArXiv at https://eartharxiv.org/s2tjd/