*4.2. Field Data*

To further examine the ground roll attenuation performance of the NA-MEMD method, we processed multicomponent seismic data from land seismic acquisition. The data included two horizontal components and one vertical component. Figure 6a–c shows the raw seismic data that are recorded X, Y, and Z components from left to right, respectively. It can be seen that seismic data in the near offset are contaminated by strong ground roll. We added three noise-assisted signals and decomposed data into eight IMFs. The ground roll with low velocity exists from the 112th to the 170th trace. Linear events with low frequency also ruin reflection waves. For each trace, we removed different numbers of IMFs. For the traces with ground rolls, we removed the first three highest index IMFs. For the rest, we removed only the first two highest index IMFs. Figure 6d–f displays the ground roll attenuation results via the NA-MEMD method for the raw three-component data, respectively. Figure 6g–i shows the ground roll and linear events separated with a low-frequency scale. From Figure 6d–f, we can see that the ground roll is successfully suppressed from the original data in Figure 6a–c.

**Figure 6.** The ground roll attenuation results for field 3C data via NA-MEMD: (**a**–**c**) the raw data, (**d**–**f**) the attenuated results, and (**g**–**i**) the separated ground roll of three-component seismic data, respectively.

To further analyze the ground roll attenuation performance of the NA-MEMD method on field data, we compared it with the F-K filter method. Figure 7a,b displays the attenuation results and differences using F-K attenuation method for the vertical component, respectively. In Figure 6f,i, we can see that the ground roll is well attenuated by the NA-MEMD method. However, the F-K method suppresses the ground roll by cutting operation in the frequency-wavenumber domain, resulting in deletion of the low-frequency content of the reflection wave. Therefore, some weak reflection event energy remains in the difference section, as shown in Figure 7b. Figure 8a,d displays the waveform and amplitude spectra from the 90th and 135th traces, respectively. Although both methods successfully

suppress the ground roll and linear interference, the NA-MEMD method preserves the reflection wave better in the low-frequency range (<10 Hz), which is important for later high-resolution imaging.

**Figure 7.** Attenuation results for vertical component in Figure 6c using F-K filter: (**a**) attenuated result; (**b**) separated ground roll.

**Figure 8.** Waveform and amplitude spectra of raw data, FK and NA-MEMD attenuation: (**a**) 90th trace; (**b**) 135th trace; (**c**) spectra of (**a**); (**d**) spectra of (**b**).
