The September 5, 2022, M6.8 Luding earthquake occurred along the southeastern segment of the Xianshuihe fault zone. Tectonics around the epicenter area is complicated and several faults had been recognized. Focal mechanisms of the main shock and inversions from earthquake data suggest that the earthquake occurred on a northwest-trending, steeply dipping strike-slip fault, which is consistent with the strike and slip of the Xianshuihe fault zone. We conducted a field investigation along the fault sections on both sides of the epicenter immediately after the earthquake. NW-trending fractures that were recognized as surface ruptures during the earthquake, and heavy landslides along the fault section between Ertaizi-Aiguocun village were observed during the field investigations. There are no surface ruptures developed along the fault sections north of the epicenter and south of Aiguocun village. Thus it can be concluded that there is a 15.5km-long surface rupture zone developed along the Moxi Fault(the section between Ertaizi and Aiguo village). The surface rupture zone trends northwest and shows a left-lateral strike slip, which is consistent with the strike and motion constrained by the focal mechanism. The coseismic displacements were measured to 20~30cm. Field observations, focal fault plane, distribution of the aftershocks, GNSS, and InSAR observation data suggest that the seismogenic structure associated with the M6.8 Luding earthquake is the Moxi Fault that belongs to the southeastern segment of the Xianshuihe fault zone. Slip along the segment south of the epicenter generated this earthquake, and also triggered slip along a northeast-trending fault and the northwestern section of the Moxi Fault in the epicenter. So, the M6.8 Luding earthquake is an event that is nucleated on the section south of the epicenter and then triggered an activity of the whole fault segment.

Xianshuihe Fault is an active fault which originated from the eastern margin of the Tibetan plateau and formed by the orogenic events in Songpang-Ganzi area. The origin of Xianshuihe Fault is discovered in the NW of Ganzi, then it extends to the SE, passing through Luhuo, Daofu, Qianning, Kangding, Luding, Moxi and disappears after passing through Shimian. Based on previous studies, Xianshihe Fault is a sinistral strike-slip fault. According to GPS and InSAR data, the horizontal component of average slip rate for Xianshuihe Fault is approximately 7.5~16.7mm/a. As a crucial member of the regional earthquake zone, Xianshuihe Fault separates Sichuan-Yunnan block and Bayankala block. More importantly, Xianshuihe Fault is responsible for a great number of large magnitude earthquakes especially in the Qianning-Kangding segment, a segment of Xianshuihe Fault which consists of three branches. From east to west, they are Yalahe Fault, Selaha Fault and Zheduotang Fault which are all active since Holocene. Yalahe Fault is responsible for a M7 earthquake that occurred around 1700AD. Selaha Fault is responsible for another M7 earthquake which occurred around 1725AD. Around 1955AD, a M7.5 earthquake occurred which was related to Zheduotang Fault.
According to the 1:50k Xianshihe Active Faults Map(1995) and relevant researches, it is discovered that, from north to south, the Holocene active Zheduotang segment starts from Kangding airport to Zheduotang village. The total length of Zheduotang segment is around 30km which includes the surface rupture zone of the 1955 M7.5 earthquake. Due to the absence of researches, the northern part of the Zheduotang Fault, which is to the north of the Kangding airport, remains unstudied. Based on satellite image, we discovered that there are signs of faults to the north of Kangding airport. Therefore, we selected four sites to carry out field investigations and trench analysis. The first site is to the NW of the Duoriagamo village. Based on satellite image and DEM data, many typical faulted geomorphologic features are discovered. To the NW of this site, both the fan and the terrace are offset. By analyzing the DEM data, the offset of T1 terrace is around 7.8m and the offset of Fan1 is around 15.6m. To the SE of this site, the fan is also offset by sinistral movement which has an offset value of 21.7m. The second site is to the NW of the Muyazuqing school where 2.6m of sinistral offset between the fan and the T1 terrace are measured. To the SE of this site, obvious offset of fan and floodplain are observed which both have sinistral offset of 2.5m. The third site is to the south of first Duoriagamo village. The fault here shows two parallel branches. The fourth site is near the Tonglilongba and there are 37.5m of horizontal offset of the fan.
Based on trench analysis, 17 stratigraphic units are defined from which carbon samples are acquired for geochronological analysis. By constraining the age of each stratigraphic unit, the age of four deformation events are defined. Event 1 is the youngest which occurred between 5 821~3 148a BP. Event 2 occurred between 13 060~10 745a BP, Event 3 occurred between 13 687~11 420a BP and Event 4 occurred between 41 443~13 715a BP. According to the integration results of our analysis, the location of northwestern segment of Zheduotang Fault is defined. It is discovered that, the NW segment of Zheduotang Fault is located between the Kangding airport and Duoriagamo village with a total length of 15km. The trace of Zheduotang Fault is also defined. From north to south, Zheduotang Fault passes through Duoriagamo village, Tonglilongba, Kangding airport, Zheduoshan nek, Ertaizidaoban and disappears near Zheduotang village. Moreover, after Holocene, the Zheduotang Fault is dominated sinistral slip movement along with minor vertical component. Different from previous researches, we believe that the Holocene active Zheduotang segment extends 15km further to the NW. This discovery provides some basis for perfecting the plane geometric images of the three active faults in Qianning-Kangding segment of Xianshuihe fault zone, such as Zheduotang Fault, Selaha Fault and Yalahe Fault, and is of great significance for understanding the strain distribution and strong earthquake rupture mode of each branch fault in Qianning-Kangding segment of Xianshuihe fault zone.

In this study, a detailed database of landslides triggered by the 25 April 2015 Gorkha (Nepal)M_W7.8 earthquake is constructed based on visual interpretation of pre- and post-earthquake high-resolution satellite images and field reconnaissance. Results show the earthquake triggered at least 47 200 landslides, which have a NWW direction spatial distribution, similar with the location and strike of the seismogenic fault. The landslides are of a total area about 110km² and an oval distribution area about 35 700km². On the basis of a scale relationship between landslide area (A)and volume (V), V=1.314 7×A^{1.208 5}, the total volume of the coseismic landslides is estimated to be about 9.64×10⁸m³. In the oval landslide distribution area, the landslide number density, area density, and volume density were calculated and the results are 1.32km^-2, 0.31%, and 0.027m, respectively. This study provides a detailed and objective inventory of landslides triggered by the Gorkha earthquake, which provides very important and essential basic data for study of mechanics of coseismic landslides, spatial pattern, distribution law, and hazard assessment. In addition, the landslide database related to an individual earthquake also provides an important earthquake case in a subduction zone for studying landslides related to multiple earthquakes from a global perspective.