Aligning microseismic reflections for imaging

Warping or receiver-by-receiver variable shifting

In a previous report, we used the general locations of ``stacked" cross-correlation peaks of the microseismic events to find a “bulk” shift to apply to the whole seismogram (Farghal and Levin, 2012). In Figure 1, we show the stack of two aligned seismograms. Extracting the reflection wavelet on the 30th channel, we can see that the highest positive magnitude is around 0.03, as shown in Figure 3 (a).

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Figure 1. Stack of two seismograms aligned by bulk shifting.

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Figure 2. Stack of two seismograms aligned by warping.

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Figure 3. a) Selected reflection (30th channel) in a stack of 2 seismograms aligned by bulk shifting. b) Close up on the reflection (30th channel) in a stack of 2 seismograms aligned by receiver-by-receiver shifting (warping). Observe the increased peak amplitude after warping.

We will now introduce receiver-by-receiver variable shifting, a limited form of warping, to align seismogram reflections within a multiplet. Figure 2 shows the stack of two aligned seismograms using this warping rather than bulk shifting. Figure 3(b) shows a closeup on the 30th channel reflection wavelet, with almost three-fold improvement in peak magnitude, confirming our better alignment of the individual seismogram reflections.

Aligning microseismic reflections for imaging