## 2 Study Area and Data  
### Study Area  
The Lake Sarez study site is located in the Rushon District of Gorno-Badakhshan province, Tajikistan, within the Pamir Mountains (Figure 1). The Pamir Mountains are part of the Himalaya-Hindu Kush-Karakorum-Pamir-Tian Shan mountain belt formed at the Indian-Eurasian collisional plate boundary [13].  
The Western Pamir and the Eastern Pamir are well divided by their physiographic characteristics. For instance, the Eastern Pamir is characterised by its mountainous plateau, whereas the Western Pamir, containing Lake Sarez, is highly mountainous with deep valleys [14]. Lake Sarez has a continental climate, mainly influenced by the Westerlies, that is responsible for the precipitation in winter and dry summers. Temperatures are moderately warm in summer and moderately cold in winter, typically ranging from \(-10\)\({}^{\circ}\)C to approaching 30 \({}^{\circ}\)C. Precipitation in this area decreases towards the Eastern Pamir due to the interception of precipitation in the Western peaks. These climatic conditions, in combination with the topography, result in mountainous vegetation, arid vegetation, shrulands, steppe, and semidesert ecosystems [15].  
The Lake Sarez region lies within the Sarez-Karakul fault zone [16], resulting in extensive fracturing of the carboniferous rock mass (sandstone, schist, quartzite) of the Sarez Formation [17]. The lake itself is situated approximately 3250 m above sea level, is 75 km long, and contains \(\sim\)17 km\({}^{3}\) of stored water. Its surrounds are characterised by the steep topography of the peaks of the Pamirs, which rise to more than 2300 m above the level of the lake. As a result of the high degree of fracturing, mass movements in the form of rockfalls and talus deposits are frequent along the slopes, particularly on the right bank of the Murghab River valley [17].  
Figure 1: The location of Lake Sarez. (**a**) The coverage of the ascending and descending Sentinel-1 frames, and (**b**) study area of interest (AOI).  
The region is seismically active, with \(M>6\) earthquakes occurring approximately every 10 years [18]. Lake Sarez was formed when a landslide dammed the Murghab River following the Sarez-Pamir Earthquake (\(M_{w}\)-7.3) on 18 th February 1911 [19]. The landslide dam, known as Usov Dam (see Figure 1b), is the largest and highest natural dam in the world, and concerns have been raised with regards to the risk it could pose should it be breached [20]. If the dam were to fail, a flood would be catastrophic to the 5.5 million people living downstream in the Amu Darya river valley, which flows through Tajikistan, Afghanistan, Turkmenistan, and Uzbekistan. The three main concerns regarding dam failure are seismic shaking, seepage, and a landslide creating a displacement wave within the lake [21]. The latter is regarded as most likely given that nearly all the surrounding slopes are susceptible to landslides due to their steep, highly fractured slopes, which could be triggered by an earthquake. Previously, in 1968, a landslide induced a 2-m-high wave across the lake [22; 23; 24]. At present, a 3 km\({}^{3}\) partially detached rock mass on the right bank (known as the Right Bank landslide; Figure 1b) is of particular concern. If triggered, the sliding or collapse of this rock mass into the lake could induce a deadly megatsunami causing water to overtop the dam [25], as has previously occurred at the Vajont Dam, Italy in 1963 [26].