Every year, landslides claim thousands of lives and cause considerable economic damage to buildings, roads, and other infrastructure around the world. As natural hazards, landslides are largely unpredictable. Improvements in the monitoring, detection, and investigation of landslides will help raise the understanding of the processes that cause these disasters and help researchers identify their early warning signs.
The requirements for a landslide are a slope and some unstable earth materials (rock and soil). Once the force of gravity exceeds the force of friction holding the rocks and soil together, a landslide occurs. The force of friction may be reduced by natural or human causes. Heavy rainfall or snowmelt, for example, can weaken the structural and mechanical stability of the ground through oversaturation. An earthquake or instability in the underlying geologic structure of the earth may also trigger a landslide. Human activity, such as mining and deforestation, may cause landslides by making the soil vulnerable to oversaturation and erosion. See also: Earthquake; Erosion; Forest soil; Landslide; Mass wasting; Mining; Rock mechanics; Soil mechanics
In 2013, G. Esktröm and C. P. Stark of the Lamont-Doherty Earth Observatory of Columbia University reported a new technique for the remote detection of rock avalanches (a form of massive rocky landslide) in real time using the Global Seismographic Network. By modeling the seismic data, they were able to estimate the location, time, size, direction, and speed of landslides and then confirm their results using satellite imagery. In addition to improving the understanding of landslide behavior, Esktröm and Stark’s work is important because remote landslides often go unnoticed—yet their remoteness does not make them nonhazardous. In mountainous regions, for example, landslides have buried entire villages without outsiders’ knowledge. Undetected landslides can also create dams in rivers that, when they subsequently rupture, can cause catastrophic downstream flooding. See also: Seismic risk; Seismographic instrumentation; Seismology
In the western United States, the U.S. Geological Survey (USGS) has set up monitoring stations with sensors that measure rainfall, groundwater pressure, ground movement, and ground vibrations. Through monitoring and detecting landslides, USGS scientists hope to be able to model the rainfall conditions that will increase the susceptibility of terrain to landslides. This information could then be used to forecast landslides, issue advisories, and save lives. See also: Engineering geology