Fresnel-zone Traveltime Tomo. for INCO and Mapleton Data Fresnel-zone Traveltime Tomo. for INCO and Mapleton Data Jianming Sheng University of Utah Feb. 5, 2004

Motivation Ray-based Traveltime Tomo. Biased towards high-velocities High-frequency assumption

Ray Distribution Depth (m) Distances (m)

Motivation Ray-based Traveltime Tomo. Biased towards high-velocities High-frequency assumption Solution 1: Wavepath traveltime tomo. Bandlimited, unbiased, multipath Wave-equation Solution 2: Fresnel-zone traveltime tomo. Paraxial ray approximation

Wavepath or Fresnel-zone s g Fresnel Zone x

First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

Principlesg First-break: high velocity First-peak: diffraction stacking First-arrivals result from First-arrivals result from diffraction stacking diffraction stacking

Misfit Function { { First-peakFirst-break

Fresnel-zone Traveltime Vasco et al. (1995) sg My Quick and dirty way: dirty way: t shift W(t)

Sensitivity Function (first-peak) Rytov Approx. (Woodward, 1992) Phaseresidual Slowness Geometricalspreading sg x t sg t sxg

Backprojecting First-break Res Depth (m) Distances (m) Depth (m) m/s m/s s g Smoothing along a fat-ray

First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

INCO Synthetic Model 080 Depth (m) X (m) m/s 0590

INCO Synthetic Data Time (sec.) 296 shots (2m) 591 rec. (1m) Dt: 0.05 ms Length: 0.3s X (m) Freq.: 90Hz Zhiyong Jiang

INCO Synthetic Model 080 Depth (m) X (m) m/s 0590 V=900 m/s L=10 m L=16.7 m V=1500 m/s V=2500 m/s L=28 m V=4500 m/s L=50 m

Ray-based Tomogram 080 Depth (m) X (m) m/s 0590

INCO Synthetic Model 080 Depth (m) X (m) m/s m 16.7 m 28 m 50 m

Fat-Ray Tomogram 080 Depth (m) X (m) m/s 0590

First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

Mapleton, Utah Data Time (sec.) shots 168 receiver Interval: 5m dt: 0.5 ms length: 1s

First-break Fat-ray Tomo Depth (m) m/s 080 Distances (m)

First-break + First-peak 0 45 Depth (m) m/s 080 Distances (m)

Migration Image 0 45 Depth (m) Distances (m)

First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

Summary A first-break and first-peak tomo. is designed. A first-break and first-peak tomo. is designed. Mapleton Data: Mapleton Data: INCO Synthetic data: INCO Synthetic data: Fat-ray tomo. provides a better tomogram This method can image complex models; More tests are necessary.

Acknowledgment I thank the sponsors of the 2003 UTAM Consortium for their financial support.