Measuring, imaging and suppressing scattered surface waves Xander Campman*, Kasper van Wijk, John Scales and Gérard Herman** * Dept. of Applied Mathematics Delft University ** Shell Int. E & P and Delft University

Near-receiver scattering

Vs=400 m/s, Vp=1700 m/s Vs=600 m/s, Vp=2500 m/s h d w Example w  d < h <<

Vertical velocity

Aligned at first breaks

Stacked

Scattered noise model

Outline of the scheme 1. Estimate velocity of the scattered surface wave  u G 2Estimate near-surface scattered energy from one isolated event. 3 Image the scattered energy  impedance distribution,  4 Predict and remove scattered surface waves on the entire record

Validation experiment A B

Seismic record, inline Direct Rayleigh wave Sound wave Ghost Rayleigh wave Scattered Rayleigh wave Cavity AB

Step 1: Estimate surface wave velocity c ~ 3000 m/s AB

Step 2: Separate scattered energy Direct Rayleigh wave : d Scattered energy : d 1 ABAB

Step 3: Estimate impedance function Impedance function:  cross-section at t=0 for entire data volume A B AB

Scattered noise model

Step 4: Predict scattered energy Ghost Rayleigh wavePredicted scattered field AB AB

Step 4: Subtract predicted scattered energy -= AB AB AB Ghost minus scattered

Transmission experiment Top view Side view AB

Transmission data AB

Step 1: Separate scattered energy First arrival : dScattered energy : d 1 AB AB

Step 2: Estimate impedance distribution Impedance function cross-section at t=0 for entire data volume AB AB

Step 4: Predict scattered field on the rest of the record AB

Input data after dip-filtering AB

Output data AB Rest minus scattered

Latest experiment

Acknowledgments Dutch Technology Foundation (STW) for financial support. Army Research Office and NSF also for financial support Everyone at PAL and CWP Shell Int. E&P and Wim Mulder (SIEP) for the use of FD code Jan Willem van den Dries for the artist impression