The gigantic Seymareh (Saidmarreh) rock avalanche, Zagros Fold–Thrust Belt, Iran

Abstract

The Seymareh rock avalanche, first described by J. V. Harrison and N. L. Falcon in the 1930s, is the largest known subaerial non-volcanic landslide on Earth. The volume of its debris (44 Gm 3 ) is approximately equal to that of the largest known subaerial landslide of any kind, the 100 ka collapse of Mount Shasta volcano (45 Gm 3 ) and approaches those of gigantic landslides on Mars. Using satellite imagery, SRTM-3 data, and detailed field investigations, we gain a new understanding of the gigantic rock avalanche. The initial failure (38 Gm 3 ), involving a dip slope consisting of a relatively weak interbedded limestone-mudrock sequence capped by resistant Asmari Limestone, had an average thickness of 410 m along a 15.5 km width of the Kabir Kuh anticline. The rockslide transformed into a rock avalanche that travelled 19.0 km with a fahrböschung (the angle between the highest point of the pre-landslide source area topography and the distal limit of the debris) of only 3.6°. Initial failure involved complex planar sliding dictated by four structural elements: (1) beddingparallel shears and (2) across-bedding break-throughs combined to produce a low-angle (11°) overall sliding surface that (3) broke out through the Asmari carapace at the toe of the failed slope while (4) tectonically weakened bedding-normal joints provided lateral release surfaces. Nine discrete bedding-parallel basal sliding surfaces divided the detached mass into nine stacked plates. The upper plate (23 Gm 3 ) included 20.7 Gm 3 of Asmari Limestone. Analysis of accelerator mass spectrometry radiocarbon dates from this study and by others indicates that the rock avalanche occurred between c. 8710 and 9800 14 C years BP.

Contributions of Rock Mass Structure to the Emplacement of Fragmenting Rockfalls and Rockslides: Insights From Laboratory Experiments

“…Dip slopes are very common in mountainous regions and form from the monoclines and anticlines in sedimentary rock. Sliding along the bedding plane or a weak interlayer is a typical failure mode of bedrock slopes and occurred in the Flims rockslide (Poschinger et al, 2006), Heart Mountain landslide in North America (Aharonov & Anders, 2006; Goren et al, 2010), Avalanche Lake rockslides and Pink Mountain rockslide in Canada (Evans et al, 1994; Geertsema et al, 2006), Saidmarreh rock avalanche in Iran (Roberts & Evans, 2013), Tagarma rock avalanche in Pamir (Wang et al, 2019), and many rockslides in central Asia (Strom & Abdrakhmatov, 2018). According to our results, this type of failure mode enhances the travel distance of the front part of the rock mass and should receive more attention in attempts to analyze the risk area of potential dip slope failure.…”

Earthquake‐Induced Chains of Geologic Hazards: Patterns, Mechanisms, and Impacts

“…Examples of very large EQTLs since 1900 include the following: Usoi, Tajikistan, 2 × 10 9 m 3 in 1907 ; Bairaman, Papua New Guinea, 1.8 × 10 8 m 3 in 1985 (King et al, 1987(King et al, , 1989; Tsaoling, Taiwan, 1.3 × 10 8 m 3 in 1999 (Chigira et al, 2003;Tang et al, 2009); Hattian Bala, Pakistan, 8.5 × 10 7 m 3 in 2005 (Dunning et al, 2007;Owen et al, 2008); and Daguangbao landslide, China, 10 9 m 3 in 2008 (Huang & Fan, 2013). Some massive prehistoric landslides are believed to have been triggered by earthquakes, such as the Seymareh rock slide, Zagros Mountains, Iran, one of the largest subaerial landslides on Earth with an estimated volume of about 4 × 10 10 m 3 (Roberts & Evans, 2013). 2018) and in other loess-mantled parts of Central Asia (Evans et al, 2009;Ishihara et al, 1990) in historical time.…”

The 2000 Yigong landslide (Tibetan Plateau), rockslide-dammed lake and outburst flood: Review, remote sensing analysis, and process modelling

“…Remote sensing, utilising digital terrain data in combination with optical imagery, is established as a vital tool in the rapid characterisation of large-scale catastrophic landslides (e.g., Evans et al, 2007;Roberts and Evans, 2013) and their process modelling (e.g., Evans et al, 2009a, b;Delaney and Evans, 2014), the determination of landslide dam geometry (Dong et al, 2014;Fan et al, 2014), and the evolution of a landslidedammed impoundment to filling and possible partial, or complete, drainage (Kargel et al, 2010;Delaney and Evans, 2011;Fan et al, 2012aFan et al, ,b, 2014Schneider et al, 2013;Yang et al, 2013;Dong et al, 2014). This use has been in parallel with the development of interest in the application of remote sensing in quantifying the geometry and volumetric storage of natural and artificial lakes in the landscape (e.g., Fujita et al, 2008;Delaney and Evans, 2011;Lu et al, 2013;Pan et al, 2013;Wang et al, 2013) and in first-order outburst process modelling (e.g., Wang et al, 2012;Schneider et al, 2014).…”