# Aerial Mapping of Coseismic Surface Rupture of 2021 M\({}_{\rm w}\) 7.3 Maduo Earthquake, China
## 4 Results
### Fault Offset  
From the data results of the drone, it can be found that some ruts, gullies, and other geographical features were displaced by fault (i.e., horizontal or vertical displacement) along the rupture zone (Figures 6 and 7). These natural and artificial markers indicate that the Maduo earthquake resulted in a primarily left-lateral strike-slip motion (Figure S3). On orthophotos, the distance between the two ends of the broken mark along the shear fracture direction was measured with the measuring tool in GIS software, and the fault offset ranges from tens of centimeters to more than one meter (Figures 6 and 7; Table S1).  
Because only a few faulted markers were directly observed in the orthophoto, some indirect markers were measured to accurately quantify the offset of the entire rupture zone. When the en-echelon shears and push-up structures were well developed within the meadow layer, by treating the push-ups as shortening structures, the compression and the amount of lateral displacement that occurred along the fault can be inferenced (Figures 8 and 9). The shortening was used as a proxy for the strike-slip fault offset; the shortening is calculated by subtracting the width of the push-up envelope from its length [20]. In practice, DEM and 3D models generated from drone data were used as baseline data. Profile data that are oriented parallel to the rupture were produced when push-ups were found in the image. After rendering the profile data with computer-aided design (CAD) software, both the length and width of the push-up were measured and the fault shortening in that particular area was calculated. Results show that the displacement shortening along the fault is on the order of tens of centimeters to about a meter (Figures 8 and 9).  
Since the above-measured offsets are all along the shear strike or perpendicular to the compression direction, the offset along the strike of the fault is equal to the measured offset divided by the cosine value of the included angle \(\theta\) between the shear strike and fault strike, or between the perpendicular direction of the push-up and fault strike [21]. The final result shows that the maximum horizontal displacement is about 2 m, which appears in the middle of the western section (Figure 10, Table S1).  
Figure 10: Offsets and main continuous surface fracture projected onto the **(A)** D-InSAR result and **(B)** satellite image. The blue bar represents the horizontal displacement. [PERSON] and yellow bars represent the vertical displacement, yellow represents the uplift of the south wall, and green represents the uplift of the north wall. The red lines indicate continuous surface fracture and deserts are distributed in the large surface rupture discontinuities.  
The vertical offset was measured directly by cutting the section in the direction perpendicular to the fault strike on the DEM data (Figures 6A and 7A). In general, only on the south branch of the western section, the south wall of the fault was uplifted, and in other sections, the north wall was basically uplifted (Figure 10). The maximum vertical offset is about 1 m. However, at this position, the fault scarp did not extend far to both sides, and no large vertical displacement was seen in the gully. Therefore, the scarp here may have a certain amount of superposition of previous seismic activity, so the vertical offset of the Maduo earthquake should be less than 1 m (Figure 7A).