Holocene paleoseismicity of the Mörtsjö fault system, Hälsingland, central Sweden

Abstract Detailed examination of LiDAR-derived imagery reveals lineations that crosscut both glacial and postglacial landforms in northwestern Hälsingland, central Sweden. Three trenches excavated across the scarps and hydroacoustical investigations in nearby lakes indicate that these are fault scarps that have ruptured to the surface multiple times since deglaciation. Trenches across the Erk-Pers segment reveal multiple landslides down the scar, soft sediment deformation structures, and till thrust over glaciolacustrine sediments. These data are consistent with the sub-bottom profiling data from nearby lakes that show the fault cutting till and glaciolacustrine sediments and at least two ages of landslides that date to early and late postglacial times. A trench across the Snaten segment of the scarp, which crosscuts postglacial raised shorelines, reveals a large landslide down the scarp that is radiocarbon dated to 3200 cal. B.P. This study adds to a growing body of the literature that suggests some glacially induced faults produced significant seismicity into the late Holocene. Graphical abstract