Sulawesi Island is located at the triple junction between the converging Australian, Sunda, and Philippine plates. The magnitude (Mw) 7.5 Palu earthquake occurred on 28 September 2018 on Sulawesi Island and caused serious casualties. The causative fault of the Palu earthquake was the left-lateral, strike-slip Palu-Koro fault, which has a rapid slip rate. We experienced this earthquake in Palu City and conducted field investigations on coseismic surface ruptures 1 d after the earthquake. Field surveys revealed that the coseismic surface ruptures were characterized by left-lateral offset, en echelon tensional cracks, mole tracks within a narrow zone, and large areas of sand liquefaction that increased the damage and losses. We measured the coseismic displacements along surface ruptures and observed a maximum coseismic offset of ∼6.2 m. The rupture traces in the north Palu Basin near Palu City mark the previously unmapped Palu-Koro fault. Based on the field investigations, we determined the exact location of the Palu-Koro fault within the Palu Basin and found that the Palu-Koro fault zone can be divided into three branches: F1, F2, and F3, forming a typical flower structure.

Abstract. Southwest China is located in the southeastern margin of the Tibetan Plateau and it is a region of high seismic activity. Historically, strong earthquakes that occurred here usually generated lots of landslides and brought destructive damages. This paper introduces several earthquaketriggered landslide events in this region and describes their characteristics. Also, the historical data of earthquakes with a magnitude of 7.0 or greater, having occurred in this region, is collected and the relationship between the affected area of landslides and earthquake magnitude is analysed. Based on the study, it can be concluded that strong earthquakes, steep topography as well as fragile geological environment, are the main reasons responsible for serious landslides in southwest China. At the same time, it is found that the relationship between the area affected by landslides and the earthquake magnitude in this region are consistent with what has been obtained worldwide. Moreover, in this paper, it is seen that the size of the areas affected by landslides change enormously even under the same earthquake magnitude in the study region. While at the same tectonic place or fault belt, areas affected by landslides presented similar outline and size. This means that local geological conditions and historical earthquake background have an important influence on landslides distribution, and they should be considered when assessing earthquake-triggered landslide hazards at Grade 1 according to ISSMGE.

Abstract. During the 12 May 2008, Wenchuan earthquake in China, more than 15 000 landslides were triggered by the earthquake. Among these landslides, there were 112 large landslides generated with a plane area greater than 50 000 m 2 . These large landslides were markedly distributed closely along the surface rupture zone in a narrow belt and were mainly located on the hanging wall side. More than 85 % of the large landslides are presented within the range of 10 km from the rupture. Statistical analysis shows that more than 50 % of large landslides occurred in the hard rock and second-hard rock, like migmatized metamorphic rock and carbonate rock, which crop out in the south part of the damaged area with higher elevation and steeper landform in comparison with the northeast part of the damaged area. All large landslides occurred in the region with seismic intensity ≥ X except a few of landslides in the Qingchuan region with seismic intensity IX. Spatially, the large landslides can be centred into four segments, namely the Yingxiu, the Gaochuan, the Beichuan and the Qingchuan segments, from southwest to northeast along the surface rupture. This is in good accordance with coseismic displacements. With the change of fault type from reverse-dominated slip to dextral slip from southwest to northeast, the largest distance between the triggered large landslides and the rupture decreases from 15 km to 5 km. The critical acceleration a c for four typical large landslides in these four different segments were estimated by the Newmark model in this paper. Our results demonstrate that, given the same strength values and slope angles, the characteristics of slope mass are important for slope stability and deeper landslides are less stable than shallower landslides. Comprehensive analysis reveals that the large catastrophic landslides could be specifically tied to a particular geological setting where fault type and geometry change abruptly. This feature may dominate the occurrence of large landslides. The results will be useful for improving reliable assessments of earthquake-induced landslide susceptibility, especially for large landslides which may result in serious damages.

Background: The Gorkha, Nepal Mw 7.8 earthquake of 25 April 2015 triggered a large number of coseismic landslides in a broad area. Two highways, Araniko Highway and Pasang Lhamu Highway, that connect Tibet of China and Nepal, were affected seriously by these landslides. The purpose of this study was to investigate the landslide damage along the two highways, construct a detailed and complete inventory of coseismic landslides in the 5-km buffer area of the Araniko Highway, and perform a regional assessment of landslide hazard in the affected area. Findings: Based on visual interpretation of high-resolution satellite images, field investigations, and GIS technology, we investigated the coseismic landslides along the Araniko Highway and Pasang Lhamu Highway. A detailed pointbased inventory of coseismic landslides was constructed and spatial distributions of the landslides were analyzed. Correlations between the landslides and five controlling factors, i.e. elevation, slope angle, slope aspect, lithology, and seismic intensity, were illustrated statistically which permitted to assess landslides hazard in a larger rectangle area.

The Xianshuihe fault in Sichuan Province, southwestern China, is one of the major left-lateral strikeslip faults that emanate from Tibet and play a key role in accommodation of India's penetration into Eurasia. In the northwestern portion of the Xianshuihe fault zone, sixteen earthquakes of M ≥6.5 occurred since 1700. The northwestern portion of the Xianshuihe fault zone can be divided into four segments based on field investigation of recent earthquake ruptures, studies on time-space distribution and recurrence behaviors of historical ruptures, geometry and structure of fault zones, geophysical background, and recent seismicity. Each segment is a fault unit that has produced historical ruptures and is able to produce future ruptures independently. In this paper, for evaluating the magnitude distribution and recurrence interval of the characterized earthquakes along the northwestern portion of the Xianshuihe fault zone, we develop a moment-balanced model by taking into account new geologic, seismologic and geodetic information, extending the previous analysis through a keener appreciation of the "stress shadow" and the influence of historical events. The result shows that all the recurrence intervals of single-segment ruptures are about 100 to 200 years, and are much shorter than the recurrence intervals of cascade ruptures and entire fault rupture.