Transient motion of the largest landslide on earth, modulated by hydrological forces

Abstract

Sea-level rise of the Caspian Sea (CS) during the early Khvalynian (approximately 40–25 ka BP) generated hundreds of giant landslides along the sea’s ancient coastlines in western Kazakhstan, which extended hundreds of kilometers. Although similar landslides have been observed along the present-day coastlines of the CS in the area of a prominent high escarpment, it remains unclear whether some of these ancient landslides are still active and whether the movement is slow or catastrophic, as previously suggested. The present study is the first to show evidence proving that the geomorphic responses to sea-level changes of the CS that were triggered in the Pleistocene are currently active. Using interferometric synthetic aperture radar (InSAR) data, we show that one of these giant landslides occurring along the western shore of the Kara-Bogaz-Gol (KBG) lagoon of the CS presents active transient motion, which makes it the world’s largest active landslide reported thus far. Extending more than 25 km along the eastern coast of the inundated KBG depression in a N–S direction with maximum landward expansion of 5 km from the shoreline to the flat Ustyurt Plateau, this landslide conveys ~ 10 × 109 m3 rocks toward the lagoon at a rate of ~ 2.5 cm/year. This event releases a nearly episodic aseismic moment of 6.0 × 1010 Nm annually, which is equivalent to the response of an Mw 5.1 earthquake. We analyze the present-day evolution of this giant coastal landslide at high temporal and spatial resolutions using Sentinel-1 radar images acquired on descending and ascending modes every 12 days between 2014 and 2020. Modelling with elastic dislocations suggests that the KBG landslide was accommodated mostly by a shallow basal décollement with a nearly horizontal listric slip plane. Moreover, our analysis reveals week-long accelerating slip events at changing amplitudes that occur seasonally with slow, lateral spreading rather than sudden catastrophic motion. A strong correlation between the episodic slip events and seasonal water-level changes in the KBG lagoon suggests a causative mechanism for the transient accelerating slip events. Although water-level changes are widely acknowledged to trigger transient motion on a land mass, such movement, which is similar to a silent earthquake, has not been observed thus far at this mega scale; on an extremely low-angle detachment planes at < 5° with modulation by sea-level changes. This study suggests that present-day sea-level changes can reactivate giant landslides that originated 40–25 ka.

Influence of Relative Sea-Level Rise, Meteoric Water Infiltration and Rock Weathering on Giant Volcanic Landslides

“…In the case of active seismicity, the acceleration of the ground surface and subsurface may generate slope destabilization. From a theoretical perspective, the slope stability depends strongly on the mechanical properties of the rocks [5], on the geometry of weakness zones, on the loading and stress conditions [2,[6][7][8][9] and on the presence of fluids [1,[10][11][12]. In volcanic areas, the interaction between magma reservoirs, magma intrusions, and pre-existing faults influences the deformation of volcanic surfaces [13][14][15] and could generate landslides.…”

Analysis of the Geological Controls and Kinematics of the Chgega Landslide (Mateur, Tunisia) Exploiting Photogrammetry and InSAR Technologies

“…The development of landslide research in countries not traditionally involved in this topic, together with continuous exploration of further territories, will surely shed new light on mass movements and emblematic landslides. The largest known landslide in the world was recently described along the coast of Kara-Bogaz-Gol lagoon (Turkmenistan) [1]. In this paper we present another outstanding landslide, identified in Northern Tunisia, on Chgega Mountain.…”

“…They undertook a study similar to ours in northern Morocco, integrating UAV-DP, InSAR, and geophysics to analyze a slow-moving landslide by the coast of the Alboran Sea. This paper complements the aforementioned case studies providing two new innovative aspects for UAV-DP and InSAR analyses: (1) we took advantage of a cloud-computing platform to perform the InSAR analyses. This platform provided us with displacement maps with no need for software or SAR images to develop the analysis.…”

Multi‐temporal InSAR analysis to monitor landslides using the small baseline subset (SBAS) approach in the Mila Basin, Algeria

“…The volumetric soil moisture was measured by the Advanced Microwave Scanning Radiometer Satellite sensor (AMSR‐E) (https://daacdata.apps.nsidc.org/). High precipitation and soil moisture measurements are recorded from November until the end of February (wet season), whereas the opposite circumstance occurs in July and August (dry season) (Aslan et al, 2021; Xu, Lu, Schulz, & Kim, 2020). Some displacement time series were selected at the critical sites affected by damage, in which the temporal pattern elucidated nonlinear and seasonal movements (Figure 11).…”

“…The interferometric synthetic aperture radar (InSAR) technique is a powerful tool for monitoring ground movement triggered by one or more conjugated factors, including hydrology (rainfall; Xu, Kim, George, & Lu, 2019), soil moisture, groundwater and surface water load (Aslan, Michele, Raucoules, & Bernardie, 2021; Ismail, Yamamoto, & El‐qady, 2021; Saroli, Albano, Atzori, et al, 2021), geotectonic (Razi, Sri Sumantyo, Widodo, Izumi, & Perissin, 2020; Saroli et al, 2021), soil strength (the presence of gley soils or shear strength reduction; North, Farewell, Hallett, & Bertelle, 2017) and irregular topography (Berardino, Fornaro, Lanari, & Sansosti, 2002; Boyd, Chambers, Wilkinson, et al, 2021; Gaebler, Ceranna, Nooshiri, et al, 2019; Hamama et al, 2022; Perissin & Wang, 2012; Selvakumaran, Rossi, Marinoni, et al, 2020; Sun et al, 2015; Sun, Hu, Zhang, & Ding, 2016; Svigkas et al, 2020). In this study, we worked to determine the rate of recent displacement occurred in the Mila Basin near the areas affected by damage.…”