Signatures of Creep in the Zunduk Fault Damage Zone on the Northwestern Coast of Lake Baikal

Abstract

The results of a high-resolution aerial survey at selected areas in the Zunduk fault damage zone trending northeast along the coastline of the Maloe sea of Lake Baikal from Cape Yadyrtuj are presented. The research was carried out within the framework of the problem of studying the seismotectonics of the shores of Lake Baikal to map the youngest surface ruptures. Based on the images obtained using DJI «Phantom 4 Pro V 2.0» unmanned aerial systems (UAS), we generated orthomosaics and digital terrain models, interpretation of which allowed us to reveal recent ruptures in alluvial fans. The largest number of them is concentrated on the Oto-Khushun Cape, where the development of disturbances as feathering structures occurs at the intersection of the Zunduk fault trending NE–SW and a proposed fault trending NNW–SSE in the water area of Lake Baikal. It explains the block structure of the rupture network in the southwestern part of the cape. Ground penetrating radar profiling showed that the surface ruptures penetrate to a depth of at least several meters. Since the last rupturing earthquake in the Zunduk fault zone is supposed to have occurred 12000–14000 years ago, the ruptures mapped in recent sediments are the result of creep events. The mechanism of their formation is associated with the periodic effect of weak seismic loads on the granular medium, as a result of which micro-slip and subsequent growth of ruptures occur. Taking into account the high rates of erosion and sedimentation within the mountain alluvial fan, as well as the persistence of disturbances in recent sediments, it can be assumed that this process is relatively constant. Identification of such brittle deformations and monitoring of their development in river deltas and outflow cones of watercourses will make it possible to predict possible places of the collapse of the coastal areas of Lake Baikal during moderate and strong earthquakes, as well as to study the dynamics of coastal development – an important component of the abiotic part of the lake ecosystem