Mud volcanism and creeping mud flows

Mud volcanism is a natural phenomenon manifesting at the surface of the body with spectacular eruptions and a large variety of morphologies resulting both from explosive and effusive activity. In this study, we targeted two large (MVs) in Azerbaijan (Lokbatan and Goturdagh) characterized by different behaviors in eruptive activity. We investigated them using a multidisciplinary approach including field observation combined with drone photogrammetry, InSAR imaging, subsurface multisource survey, geotechnical analyses of mud breccia flows and numerical stability modeling in order to reveal the way the mud flows.

Lokbatan most recently erupted in August 2022. Field observations in September 2022, before significant modification by rain, reveal that this most recent eruption, albeit small in terms of extruded mud breccia, triggered the disruption of huge segmented portions of the older mud flows that extend for more than 1 km. This was identified by the formation of series of fractures recording the detachment and subsequent downhill movement of the old flow. No evident ground deformations have been observed before the eruption and, repetitive field campaigns in subsequent months do not reveal any network of fresh fractures and dislocations. On the other hand, Goturdagh MV features a constant slow extrusion of compacted mud breccia from the subsurface forming an extended >1.2 km long mud flow that continuously moves. This movement is clearly visible at the top of the MV where repetitive field observations reveal an extrusion of wet and dark colored mud breccia. Along the slope, the movement creates well-developed shear zones and compressional structures typical of slope deformations. At the bottom however, the movement seem to be discontinuous and might be triggered occasionally when the force of the new material becomes critical.

The field observations show that kilometer scale mass transport can extend at MVs for more than 1 km along the flank of these structures. The additional approaches will help us identify possible eruptive precursors and understand if external elements (tectonics, rainfall, …) can influence this mass movement. The same phenomenon is likely happening at many other large-scale features worldwide.