# 2-D Cross-Plot Model Analysis Using Integrated Geophysical Methods for Landslides Assessment
## 4 Discussion
Figure 9 shows the correlation of borehole and geophysical results for line HR1 and HS1 with BH10 and HR2 and HS2 with BH9 at a distance of 225 m and 175 m, respectively. In Figure 9a, the borehole record, BH10, shows the record with investigation depth about 8.5 m from the surface. The result showed a much lower \(N\)-value at a depth range of 0-2.5 m that shows a low stiffness of soil for this particular point. At this depth range, both 2-D resistivity and seismic refraction show no data availability due to the blanking effect during processing. As the borehole reaches at depth >3 m, the record shows the drastic increases of the trend where \(N\)-value of 50 blows were recorded until the end of the borehole. From this, \(N\)-values of 50 blows show that the compacted or stiffer/very dense soil was reached as the rock head was recorded at a depth of 5.5 m from the surface. In addition, both 2-D resistivity and seismic refraction shows convincing correlation at a depth of >3 m, the resistivity shows the value of 1600 \(\Omega\)m consistently until the depth of 5 m, and increases >3500 \(\Omega\)m at depth >5 m. The proportional increases of the resistivity values indicate the changes of soil stiffness as the values >3500 \(\Omega\)m indicate the weathered bedrock/boulder. In the seismic profile, at depth ranges of 3-5 m, the velocity is represented by the values of 800-1400 m/s and increases >1800 m/s at depth >5 m. The velocity of 800-1400 m/s indicates the medium stiffness of the soil, which probably shows the weathered layer for the material as the  
Figure 8: Three-dimensional (3-D) model of resistivity result with Gapis River pathway. velocity increases \(>\)1800 m/s corresponding with the \(N\)-value of 50 blows, as rock head was found at a depth of 5.5 m. The velocity shows the increase in trends at a depth of \(>\)8.5 m as investigation depth cover ups to 25 m with velocity ranges of 1800-4200 m/s. The wide ranges, with proportional trends of the velocity, show the increased strength of soil material, as the bedrock was interpreted with values of \(>\)3400 m/s. In other profiles of borehole records of BH9, only line HR2 was in line at a distance of 175 m as HS1 showed limited survey distance, as shown in Figure 9b. The borehole record shows a deeper depth of investigation, up to 33 m from the surface. However, at this particular distance, the resistivity shows no data availability due to signal coverage at a depth \(>\)15 m. Only the depth range of 1.5-15 m was used to correlate with \(N\)-values data. From the record of BH9, it was clearly seen the variation of \(N\)-values that represents the heterogeneous condition with different soil stiffness at depth \(<\)10 m. The \(N\)-values show a lower number of blows from the range 1-10 at this depth, which indicates low stiffness or represents loose material for this depth range, as the resistivity shows the variation of values of 150-800 \(\Omega\)m. As the depth increases, at depth 12 m the borehole record shows the \(N\)-value of 50 blows for this particular depth, and decreases at a depth of 13-15 m, where N-values were recorded \(<\)5 number of blows. The upsurge decreases of N-values from 50, which indicate this layer consists of very poor conditions that shows very loose material was underlined. However, the \(N\)-values show the gradual increases from 18-50 of \(N\)-values, up to a depth of 27 m from the surface. In resistivity profiles, the values show the gradual changes of resistivity distribution from a range of 500-1200 \(\Omega\)m up to the depth of 15 m, as the data were not available above that depth. The borehole record shows a consistent number of blow at depth 27-33 m with values of 50, which indicate the hard layer (medium dense) for these profiles as no indicator was marked as bedrock compared to others boreholes. The schematic diagram of soil classification, [78] based on the distribution of \(N\)-value for BH7-BH10 are shown in Figure 9c. Noted that BH7-BH8 was located in the landslide area.