## 4 Results
### New Geological-Structural Data  
During the present work, we mapped a total of 1355 fractures classified as normal faults (86) and extension fractures (1269): these structures strike from NNW-SSE to NE-SW, but are mostly in the range N0-20\({}^{\circ}\) E, whereby the av. strike is N8.2\({}^{\circ}\) E, as shown in the rose diagram in Figure 6b. The longest fracture reaches a length of 1156.1 m, whereas the overall av. length is 28.3 m (Figure 6e). Although the whole Krafla rift has an about N-S elongation, once you define the structures in detail it emerges that several single faults have a bimodal strike given mostly by N-S and NNE-SSW segments, with a curvilinear trace in plan view. Owing to the high resolution of the new DSM and orthomosaic, the number of mapped fractures is dramatically greater with respect to the 45 main fractures documented on the 1:100,000 scale geological map ([PERSON] et al., 2018) (Figure 1b). In addition to the newly mapped fractures mentioned above, we have also redrawn the geological map of the area, tracing with very high detail the geological limits, as shown in Figures 6a and 7. In regard to normal faults, they mainly strike from N-S to NE-SW, dipping towards WNW and ESE (Figure 6c), and show an overall av. and maximum length of 167.9 m and 1156.1 m respectively (Figure 6e). On the other hand, extension fractures mainly strike from NNW to NNE, with an av. value of N8.1\({}^{\circ}\) E (Figure 6d), and an overall av. and maximum length of 18.8 m and 240.7 m respectively (Figure 6e). In order to better define the deformation processes that have been occurring since late Pleistocene times, we collected a series of quantitative data at a total of 852 sites, 284 along normal faults and 568 along extension fractures. Regarding normal faults, we collected 284 vertical offsets, thus obtaining a maximum value of 42 m along faults affecting LGM units and of 19 m along faults affecting post-LGM units (Figure 7). Regarding extension fractures, we collected a total of 1704 structural data, consisting of strike, opening direction and fracture dilation, at 568 different sites(Figure 7): all these data have been collected in the post-LGM units (no extension fractures in historical lavas or in LGM units). Figure 7: Vertical offset values for normal faults (red lines), opening direction and dilation for extension fractures (cyan lines) are reported. The legend for the geological units is the same as in Figure 6a. The rose diagram shows both extension fracture strikes and opening directions. For each set of data, the av. value and standard deviation is represented as continuous and dashed lines respectively, the regional spreading direction range is reported as dark grey lines. Opening direction values are in the range N46.3-142.3\({}^{\circ}\) E, with a mean value of N97.7\({}^{\circ}\) E and a SD of 13.3\({}^{\circ}\): only 109 values fall within the spreading direction range (N104-115\({}^{\circ}\) E), which is based on spreading direction estimates given in the literature for the NVZ [17; 54; 57; 58; 59; 60; 61]. We also measured the extension fracture azimuth that ranges N48.1\({}^{\circ}\) W-N61.5\({}^{\circ}\) E, with a mean value of N7.9\({}^{\circ}\) E and a SD of 18.5\({}^{\circ}\): only 119 values show an azimuth that is compatible with the spreading direction range. If we consider both the extension fractures opening direction and strike, only 43 out of 568 are compatible with the spreading direction range N104-115\({}^{\circ}\) E (Figure 8a). The dilation is in the range of 0.1-4.1 m, with a mean value of 0.64 m and a SD of 0.5 m. Figure 8b shows the relation between fractures strike and amount of opening: we observe that most of extension fractures with a dilation \(>\) 1 m have a strike between NNW-SSE and NE-SW, and the wider fractures are characterized by an opening direction N80-120\({}^{\circ}\) E (Figure 8c) and a lateral component \(<\) (+/-) 20\({}^{\circ}\) (Figure 8f).