RFG 2018 Conference

landslide

USGS approach to real-time estimation of earthquake-triggered ground failure - Results of 2015 workshop

The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developing plans to add quantitative hazard assessments of earthquake-triggered landsliding and liquefaction to existing real-time earthquake products (ShakeMap, ShakeCast, PAGER) using open and readily available methodologies and products. To date, prototype global statistical models have been developed and are being refined, improved, and tested. These models are a good foundation, but much work remains to achieve robust and defensible models that meet the needs of end users. In order to establish an implementation plan and identify research priorities, the USGS convened a workshop in Golden, Colorado, in October 2015. This document summarizes current (as of early 2016) capabilities, research and operational priorities, and plans for further studies that were established at this workshop. Specific priorities established during the meeting include (1) developing a suite of alternative models; (2) making use of higher resolution and higher quality data where possible; (3) incorporating newer global and regional datasets and inventories; (4) reducing barriers to accessing inventory datasets; (5) developing methods for using inconsistent or incomplete datasets in aggregate; (6) developing standardized model testing and evaluation methods; (7) improving ShakeMap shaking estimates, particularly as relevant to ground failure, such as including topographic amplification and accounting for spatial variability; and (8) developing vulnerability functions for loss estimates.

The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County, Colorado

On May 25th, 2014 the longest landslide in Colorado’s historical record occurred in west-central Colorado, 6 mi southeast of the small town of Collbran in Mesa County. Three local men perished during the catastrophic event. The landslide was 2.8 miles long, covered almost a square mile of the West Salt Creek valley and the net volume displacement was 38 million yd3. The fast-moving (40-85 MPH), high-mobility landslide was caused by an initial rotational slide of a half-mile-wide block of Eocene Green River Formation. The resultant rock failures, rockmass disaggregation, and mostly valley-constrained rock avalanche, dropped approximately 2,100 ft in elevation as a rapid series of cascading surges of chaotic rubble composed of fragments of pulverized rock, vegetation, topsoil, and mud. Local seismometers recorded a magnitude 2.8 earthquake from the event with a seismic wave train duration of approximately 3 minutes. The toe of the landslide came within 200 ft of active gas-production wellheads and loss of irrigation ditches and water impacted local ranches and residents

The report covers the regional setting, evidence of past landslide activity, landslide modes of failure, rock avalanche morphology, triggering mechanisms, monitoring, long-term hazard assessment, and land-use recommendations. A geologic map and cross section are also included.

The geologic context of landslide and rockfall maintenance costs in Kentucky

Kentucky Transportation Cabinet maintenance cost data for landslides and rockfalls were associated with geology along Kentucky roadways in a three-phase study. Work-order costs collected over 7 yr were divided into 1-mi segments, and the segment midpoints were assigned to geologic units in order to assess the most costly and frequently repaired segments according to geologic formation. Formations that were expensive to maintain were not necessarily those that were the most frequently repaired and vice versa. Costs and frequency of repair were greater in eastern and northern Kentucky, where slope and relief are greater than in other parts of the state and shale-bearing geologic units prevail.

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