# Seismic Response of Loess-Mudstone Slope with High Anti-Dip Angle Fault Zone
## 1 Introduction  
Western China has complex geological conditions, with active tectonics and frequent seismic activities. Between 1949 and 2009, a total of 1679 earthquakes with magnitudes greater than 5.0 occurred in China, of which 1547 (92.14%) occurred in Western China [1]. Loess is distributed widely in this region, with a distribution area of 633,500 km\({}^{2}\) and a complex and diverse genetic type; it accounts for 6.63% of the total land area in the entire country [2]. The instability of loess slopes during earthquakes is well-researched because such instability often results in serious landslide disasters, which threaten the personal and property-related safety of the residents in the surrounding areas. For example, in 1718, 59 loess landslides with ranges greater than 500 m were induced by the Gansu Tongwei earthquake (Ms = 7.5). In 1920, a loess landslide with an area of over 4000 km\({}^{2}\) was triggered by the Haiyuan earthquake (Ms = 8.5). More than 150 loess landslides wereinduced by the Gansu Yongdeng earthquake (Ms = 5.8) in 1995 [3] and on 22 July 2013, an earthquake (Ms = 6.6) in Min-Zhang County, Gansu Province, resulted in more than 600 loess landslides [4; 5]. The occurrence of these earthquake-induced loess landslides is related to the existence of active fault zones, which clearly affect the distribution and development of earthquake-induced landslides in western China [6]. Many studies have been carried out on the dynamic response and stability of slopes during earthquakes. The theory of sliding liquefaction has been proposed by [PERSON] et al., [PERSON] et al., and [PERSON] [7; 8; 9], who argue that liquefaction occurs in the sliding body under the action of forced vibration. Through dynamic triaxial liquefaction tests of loess from the central United States, loes liquefaction under cyclic dynamic loadings and seismic liquefaction slip of the loess layer were rigorously analysed by [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [10; 11; 12; 13; 14]. The finite slip displacement method was proposed by [PERSON] [15], which provided a new idea for the quantitative evaluation of slope dynamic stability. It was subsequently confirmed that stability evaluation using this method is reliable [16; 17], and it was developed and improved by [PERSON], [PERSON], and [PERSON] et al. [18; 19; 20]. [PERSON] et al. [21] proposed an efficient finite element method, based on the quasi-static method, with which to evaluate the dynamic stability of soil slopes. [PERSON] [22] placed monitors in Nevada, USA, and found that vibration at the high point of the terrain was stronger than that on a relatively flat area. Furthermore, investigations found that the obvious topographic amplification effect caused by the 1989 San Francisco and 1994 Pacific Northridge earthquakes was the cause of several landslides [23; 24]. The factors influencing slope stability during earthquakes and the slope instability mechanism were summarised by [PERSON] et al. [25], indicating that seismic inertia force and the building up of excess-static pore pressure are two reasons for the induction of the instability of a slope. The characteristics of the distribution of earthquake-induced landslides in loess areas and the main factors affecting such landslides were analysed by [PERSON] et al. [26], by building a classification model based on the AHP method and indicating that the classification model is appropriate to the loess landslide zoning. [PERSON] et al. [27] carried out several ring shear tests on loess soil formed by the landslide induced by the Haiyuan earthquake to study the formation mechanism of earthquake-induced loess landslides, and they indicated that the pore pressure was built-up gradually before the failure, and after that, that large pore pressure was quickly generated due to the failure of the loess soil structure. The deformation and failure characteristics of large-scale loess landslides triggered by the 1949 Khait earthquake in Tajikistan were studied by [PERSON] et al.