passive seismic imagingsep/crustal research group brad@sep.stanford.edu 1 return to passive imaging...

brad@sep.stanford.edu

Passive Seismic ImagingSEP/Crustal Research Group

Return to Passive Imaging

Brad Artman

June, 6 2002

Ph.D. Proposal

State of Affairs

Claerbout’s Conjecture

Terra/Helio-seismology EngineeringExploration

Success

• The nutshell

• Why it works

• As it stands

• Toward the goal

• How to finish

• When will all this be ready?

• The nutshellThe nutshell– ProblemProblem– ImportanceImportance– ProposalProposal

• Why it works

• As it stands

• Toward the goal

• How to finish

Problem

• Who knows if passive seismic imaging works?– Why (not)?

Importance

• Lots of people care about the subsurface.

• No source required opens opportunities for:– Monitoring– Reconnaissance– Restricted access sites– Old long data sets– New long data sets

Proposal

I propose to answer whether or not the passive seismic experiment can be used as a practicable methodology for subsurface imaging and/or monitoring.

+ or - I’ll tell you why.

• The nutshell

• Why it worksWhy it works– Intuitive explanationIntuitive explanation– Rigorous explanationRigorous explanation

• As it stands

• Toward the goal

• How to finish

Intuitive explanation

r1 r2 r1*r1 r1*r2

Rigorous explanation I

Conventional reflection seismic

Earthquake seismology

Y –R( ) R(Z) + [1+R( )] [ 1+ R(Z)] = Y U( ) U(Z)Z1

1+R( ) R(Z) = a U( ) U(Z)Z1

Rigorous explanation IY –R( ) R(Z) + [1+R( )] [ 1+ R(Z)] = Y U( ) U(Z)Z

1+R( ) R(Z) = a U( ) U(Z)Z1

Conventional reflection seismic

Earthquake seismology

Intuitive explanation

r1 r2 r1*r1 r1*r2

Rigorous explanation II

U( ) U(Z) = U(p,ω) U(p,ω) = Q(p,ω)Z1

Q(k,ω) = Q( , ω) = |ω|U(k,ω) U(k,ω)1|ω| ω

Q(p,ω) = Q( , ω)ω k

Q(p,ω) = |ω| Q(k,ω)

q(x,t) = (t) u(x’,t) u(x+x’,t+t’)t’x’

rx’,x+x’(t)x’

Synthetic Testsm

Cross-correlation Technique

Passive Seismic Imaging applied to synthetic data, Rickett SEP-92

Virtual multiples

r1 r2 r1*r1 r1*r2

• The nutshell

• Why it works

• As it standsAs it stands– It works!It works!– On the shoulders of giantsOn the shoulders of giants– The raceThe race

• Toward the goal

• How to finish

It works!

Acoustic Daylight Imaging via spectral factorization, Rickett SEP-100

On the shoulders of giants• SEP reports 60 – 86, 100

– SEP’s Franciscan effort and analysis

• Schuster– Correlation migration– Drill bit source

• Bostock– Earthquake array seismograms

• Louie– Engineering characterization

The Race

• Undisclosed submission

• Company interest

• Livermore???

• The earth from satellite?

• The nutshell• Why it works• As it stands• Toward the goalToward the goal

– Is 2D possible?Is 2D possible?– Reformulation as migrationReformulation as migration– Motivation to invertMotivation to invert– Sampling the noise-fieldSampling the noise-field– Shape of the noise-fieldShape of the noise-field– Artman GeoServicesArtman GeoServices

• How to finish• When will all this be ready?

Is 2D possible?

• Yes

• PGS OBC 3C Co-parallel PSD !

Is 2D possible?, Artman, SEP-111

Reformulation as migrationI(z, x)=Σ P (ω,x,s) P (ω,x,s)

P is the wave field at each depth level,where source and receiver fields are propagated independently via SSR.

Realization: If P = P , correlation requirement of the passive seismic conjecture

is fulfilled in the migration.

Let the wave equation handle the unknown source.

Areal Source Wave-fieldShot-profile migration of multiple reflections,Guitton, SEP-111

Synthetic Testsm

Two horizontal planesm m

Point Diffractor

Cost Comparison

• Correlations– Spatial increase: N to N (+5 O.M.) – Temporal decrease: N to N (- 4 O.M.)– Migrate (S.P.): N N N N

• Skipping Correlations– No spatial or frequency change: N , N– Migrate (S.P.): N N N N

lag zxy2

t zhxy

Motivation to invert

Sampling the noise-field

Minimize storage and processing costsBow to acquisition computer limitations

Shape of the noise-field

Artman GeoServices

• The nutshell

• Why it works

• As it stands

• Toward the goal

• How to finishHow to finish– Brad, the sun, and your coffee tableBrad, the sun, and your coffee table– Santa Clara Valley Seismic ExperimentSanta Clara Valley Seismic Experiment– Recast as deconvolutionRecast as deconvolution– Wave-field separationWave-field separation

Solar imaging

• Flare structure, density layering

• Tools: – Absorbing boundary layer modeling– Up-down extrapolator

• James Rickett

Crustal Seismic

Deconvolution• Who needs physics?

U = T SS = H W

A U = WA = W W H T -1 -1 -1

= H T-1-1

Assume T is white(ish) and events are well spaced-1

Second PEF estimation & application returns T-1

Levinson recursion calculates the reflection coefficients

Wave-field separation

u = E L R

Up-going wave-field

Physics

Surface displacements

E has azimuthal dependency- this may not work.

Data commitments• Linear acquisition:

– S. California, USGS. Sept. 2002

– S.C. Valley, USGS. Sept. 2002

– 3C OBC, GoM, PGS, June 2002

– Unspecified test, PGS, Sept. 2002

– Publicly available seismologic deployments

• Areal acquisition:– South Texas, CGG, Sept. 2002

– Sun, SOI, in-house

– S.C. Valley, USGS, in-house

– Moss Landing +, Artman GeoServices, in-house

– Publicly available seismologic deployments

Time-line

• Summer 2002– 3D up-down extrapolator, absorbing BC’s– Image solar flare, submit for publishing– Image Moss Landing beach

• Urban applications?

– Continue collection of outside data– SEG passive seismic workshop

Time-line

• Fall 2002– Image Santa Clara Valley, submit for publishing– Gather/acquire data– Image data as it arrives– Physics 210: Particle mechanics

Time-line

• Winter 2002-Spring 2003– Continue data collection and processing– Comp. Sci. 238: Parallel methods in num. analysis– Begin comparative study of successes and failures– Prepare work for publishing

• Summer 2003 – outside internship

Time-line

• Fall 2003 – Spring 2004– Finalize comparative analysis– Define success parameters– Prepare for publishing

• Summer 2004– Stat. 110: Stat. Methods in eng. and phys. science– Wrap up outstanding projects

Time-line

• Fall – Winter 2004– PE 284 : Optimization– Write thesis, journal articles

• Spring 2004– Finalize deliverables for graduation

Thank You

passive seismic imagingsep/crustal research group brad@sep.stanford.edu 1 return to passive imaging...

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