Evidence for Large Holocene Earthquakes Along the Denali Fault in Southwest Yukon, Canada

The Yukon–Alaska Highway corridor in southern Yukon is subject to geohazards ranging from landslides to floods and earthquakes on faults in the St. Elias Mountains and Shakwak Valley. Here we discuss the late Holocene seismic history of the Denali fault, located at the eastern front of the St. Elias Mountains and one of only a few known seismically active terrestrial faults in Canada. Holocene faulting is indicated by scarps and mounds on late Pleistocene drift and by tectonically deformed Pleistocene and Holocene sediments. Previous work on trenches excavated against the fault scarp near the Duke River reveals paleoseismic sediment disturbance dated to ∼300–1,200, 1,200–1,900, and 3,000 years ago. Re-excavation of the trenches indicate a fourth event dated to 6,000 years ago. The trenches are interpreted as a negative flower structure produced by extension of sediments by dextral strike-slip fault movement. Nearby Crescent Lake is ponded against the fault scarp. Sediment cores reveal four abrupt sediment and diatom changes reflecting seismic shaking at ∼1,200–1,900, 1,900–5,900, 5,900–6,200, and 6,500–6,800 years ago. At the Duke River, the fault offsets sediments, including two White River tephra layers (∼1,900 and 1,200 years old). Late Pleistocene outwash gravel and overlying Holocene aeolian sediments show in cross section a positive flower structure indicative of post-glacial contraction of the sediments by dextral strike-slip movement. Based on the number of events reflecting ∼M6, we estimate the average recurrence of large earthquakes on the Yukon part of the Denali fault to be about 1,300 years in the past 6,500–6,800 years

Satellite interferometry for regional assessment of landslide hazard to pipelines in northeastern British Columbia, Canada

Pipelines are a critical component of transportation infrastructure. They offer the safest and most efficient way to transport large volumes of oil and natural gas from development areas to refineries and consumers. Landslides can damage pipelines resulting in a spill of a toxic substance. However, landslide hazards to pipelines and other infrastructure can be significantly reduced, if the location of landslides is known and the appropriate mitigation measures are taken in advance. Traditional, ground-based methods for mapping areas susceptible to landslides can be expensive and limited. Radar interferometry is a remote sensing technique that measures ground deformation from two Synthetic Aperture Radar (SAR) images. Time series of ground deformation computed from repeatedly acquired SAR data allows us to detect slow-moving, deep-seated landslides over a large area with high spatial resolution and precision. European Space Agency’s Sentinel-1 satellite systematically collects SAR data worldwide, and large datasets have been collected since approximately 2016–2017. A combination of improved availability of SAR data, inexpensive processing power and advanced processing techniques designed for large datasets provides an opportunity to map ground deformation on a regional scale. The study’s objective is to compare deformation maps, as proxies for landslide identification, computed from commercial RADARSAT-2 data and freely available Sentinel-1 data over a region in northeast British Columbia, Canada, with an extensive network of pipelines. It is concluded that readily available Sentinel-1 data can produce high-quality deformation maps capable of detecting slow-moving landslides. In the study area, hundreds of slow-moving landslides are mapped using hotspot analysis based on Getis–Ord Gi∗ statistics, and two small regions where landslide activity near the pipelines is particularly significant are studied in detail. Field observations also revealed that slope deformation features formed in the surface sediments consist of colluvium derived from a mix of glaciolacustrine, till and fine-grained sedimentary bedrock

A revised earthquake chronology for the last 4000 years inferred from varvebounded debris-flow deposits beneath an inlet near

Abstract A reanalysis of the varve chronology from hydraulic piston sediment cores was carried out to establish better uncertainty estimates on ages of prehistoric debris-flow deposits (DFDs) in the last 4000 yr. Saanich Inlet is an anoxic fiord located in southeast Vancouver Island near the city of Victoria, British Columbia. It contains annually laminated (varved) marine mud deposited in anoxic conditions. Interlayered with these Holocene varves are massive layers of coarser sediments deposited by submarine debris flows. It has been previously interpreted that these flows were induced by earthquake shaking. Two of the DFDs correspond to known earthquakes: A.D. 1946 Vancouver Island (M 7.3) and the A.D. 1700 Cascadia plate-boundary subduction earthquake (M 9). Based on varv