## 3 Shallow P-Wave Data Example  
In the following we will conduct a detailed comparison between the three search strategies presented in the previous section. For this purpose, we reprocessed seismic line 2 of a P-wave data set acquired, processed and interpreted by [46]. CRS stack results for the less noisy line 1, obtained using the pragmatic search strategy, are discussed \begin{table}
\begin{tabular}{c c c c} \hline \hline
**3 \(\times\) 1 Pragmatic** & **1 \(\times\) 3 One Step** & **1 \(\times\) 2 One Step** & **Computational Effort** \\ \hline
10 + 10 + 10 & 10 \(\times\) 10 \(\times\) 10 & 10 \(\times\) 10 & Coherence calculations \\
1 & 5 & 5 & CMPs per coherence \\
30 & 5000 & 500 & Total effort \\
1 & 166 & 16.6 & Relative effort \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Assuming a 10 point per dimension search grid without refinement and 5 CMP gathers per CRS/CDS aperture, we obtain the depicted values for the three methods discussed. Figure 4: Sensitivity analysis of the CRS traveltime with respect to reflector dip, reflector curvature and stacking velocity. Figure taken from [45]. in [47]. The acquisition, which took place in the South-East of Sardinia, the second largest of Italy's islands, can be categorized as a hydrogeological survey. In Sardinia, water is a precious resource, frequently in short supply during the long, hot, and dry summer, creating distribution conflicts between agriculture and tourism, as well as environmental problems, such as the salinization of coastal aquifers. The two lines, having a length of 1.1 km each, cross the coastal plain of the Flumendosa River, on the southeastern coast of Sardinia, Italy, roughly parallel to the coastline of the Tyrrhenian Sea. The survey was aiming both at imaging the Paleozoic bedrock topography, and at obtaining detailed structural and stratigraphic information on the sequence of largely fluvial sediments extending from the surface down to bedrock. The study aimed to gain a better understanding of the geological and hydrogeological factors influencing a highly productive aquifer located in thick Quaternary deposits and subject to extensive saltwater intrusion. For a detailed description of the geological and hydrogeological features of the target area we like to refer to [46]. The 89 shot-gathers were recorded using a standard common-midpoint (CMP) roll-along technique in an end-on configuration with 48 active 50-Hz geophones. At every shot point, 0.25-kg of explosives were fired. The sources were placed at a depth of 2 m, which lay in general below the water table. Geophone spacing of 5 m and source spacing of 10 m provided twelvefold CMP coverage with a CMP spacing of 2.5 m. The recorded traces had a sample interval of 0.5 ms and a record length of 1024 ms. Expecting a maximum reflector depth of 200-300 m a maximum source receiver offset of 245 m was chosen, which was right for line 2, where the maximum depth of the basement turned out to be ca. 200 m.  
Three representative shot gathers, for the sake of simplicity called records in the following, are shown in Figure 5. In all records, the airwave (event \(e\)) is clearly visible. An up-dip reflector at the beginning of the line is presumably related to event \(f\), with clear reversed moveout from record 3 and visible up to record 11. On the other end of the line where record 72 was selected as representative sample record, event \(g\) can be interpreted as refracted arrivals, stemming from a very shallow refractor, corresponding to the interface between the bedrock and the overlying sediments. Figure 5: Raw field records from three locations along the seismic line (see arrows in Figure 13a), according to [46]. Automatic Gain Correction (AGC) with a 100 ms time window was applied to enhance the different seismic events for the display. Line 2 terminates on the southern bank of the Flumentosa River, 140 m from a Paleozoic outcrop.