Supervirtual Interferometric Separation and Enhancement of Backscattered Surface

Super-virtual Interferometric Separation and Enhancement of Back-scattered Surface Waves Bowen Guo*, Sherif Hanafy, Gerard Schuster King Abdullah University of Science and Technology

Outline Ø Motivation Ø Theory Ø Numerical results Ø Conclusion and future work fault

Motivation Ø Back-scattered surface waves (BSWs) can be migrated to detect nearsurface structures Shot Gather Virtual BSWs Shot Gather of Surface Waves 0. 0 0. 5 t(s) Ø Problem: weak amplitude, masked by incident surface waves, so that difficult to be separated Ø Solution: super-virtual interferometry (Bharadwaj et al. , 2011; Dai et al. , 2011) to separate and enhance BSWs t(s) 0. 0 1. 6 km/s 0. 3 0 500. 0 X (m) 2. 2 km/s 150 1. 6 km/s X (m)(Yu et al. , 2014) 300 X (m)

Outline Ø Motivation Ø Theory Ø Numerical results Ø Conclusion and future work

Theory: super-virtual interferometry by cross-correlation fault

Theory: super-virtual interferometry by cross-correlation fault

Theory: artifacts from the cross-correlation Ø Artifacts in Cases 1 and 2 fault Artifacts can be muted because they arrive earlier than incident surface waves

Theory: super-virtual interferometry by convolution fault *

Work Flow Step 1: Mute body waves. No need to be Step 2: Retain incident surface waves and mute other events. accurate Step 3: Retain BSWs and mute other events. Step 4: Use SVI to calculate virtual BSWs

Outline Ø Motivation Ø Theory Ø Numerical results Ø Conclusion and future work

Synthetic Example 0 S-wave Velocity m/s 800 t (s) Z (m) CSG with Noise 0 Scattered Surface Wave with Noise 0 t (s) 500 60 0 X (m) 0 500 300 1. 2 0 Virtual BSWs by Correlation Artifacts t (s) X (m) 500 Virtual BSWs by Convolution 0 BSWs 1. 2 0 0. 7 X (m) 500 Trace Comparison Noised BSWs True Data t (s) BSWs by Correlation 1. 2 0 X (m) 500 1. 2 0 Normalized 1 Amplitude BSWs by Convolution

Field Data Example 0. 0 Common Shot Gather (CSG) Gulf of Aqaba Data in Saudi Arabia Ø 120 shots and 120 receivers t(s) Ø Source/receiver sampling interval 2. 4 m 0. 3 0 X (m) 300

Field Data Example CSG 30 Mute Body Waves 0. 0 t(s) 0. 3 0 0. 0 X (m) Incident Surface Waves 300 0 0. 0 X (m) 300 Virtual BSWs t(s) 0. 3 0 0 X (m) 300

Field Data Example 0. 0 CSG 38 t(s) 0. 3 0 0. 0 X (m) CSG 40 300 0. 3 0 0. 0 X (m) Virtual BSWs 40 300 t(s) 0. 3 0 Virtual BSWs 38 0. 0 X (m) 300 0. 3 0 X (m) 300

Field Data Example Virtual BSWs 38 0. 0 Velocity Tomogram 0 Z (m) 40 0 t(s) 150 (m) 400 0. 3 0 0. 0 X (m) Virtual BSWs 40 Resistivity Tomogram Z (m) 40 0 X (m) 300 (m) 150 (m) 1 0. 3 0 2800 300 0 t(s) Velocity (m/s) 300 (m) Resistivity (Ohm. m) 500

Outline Ø Motivation Ø Theory Ø Numerical results Ø Conclusion and future work

Conclusions Ø Back-scattered surface waves can be enhanced and separated by SVI Ø No need for velocity, robust Future Work Ø 2 D 3 D

Acknowledgement We would like to thank King Abdullah University of Science and Technology for their support Thank you for your attention