Geologic hazards are responsible for great loss of life and destruction of property. In the twentieth century more than a million people worldwide have been killed by earthquakes alone, and the value of the property destroyed by earthquakes, volcanoes, and tsunamis amounts to several billions of dollars.
Landslides are responsible for significant loss of life to people and their livestock as well as damage to infrastructures, agricultural lands and housing. They are recognized as the third most deadly natural disaster worldwide with an estimated death toll per year in the thousands. Most landslide fatalities are from rock falls, debris flows, or volcanic debris flows (lahars).
Another common geologic hazard is the presence of sinkholes. Natural sinkholes change the general topography of the area and divert streams of underground water. If they form suddenly in areas with heavy population, they can cause a lot of damage to human life and property. Some holes are formed due to the leak in underground storm drains and sewer systems. They can be dangerous to the foundations of buildings. Sinkholes occur commonly in areas where there is an abundance of carbonate rocks or evaporitic formations.
The consequences of slope instability can be costly and even result in the loss of many lives. Any slope failure can result in substantial costs for remediation while in regions of dense population or areas prone to high velocity landslide, the loss of life can be considerable. Therefore, governments and private agencies are increasingly asked to manage the hazard of slope instability.
There are a number of possible factors that can lead to the instability of a soil slope. However, in general, earthen slopes remain stable unless there are changes in the pore-water pressures in the soil comprising the slope. Changes in pore-water pressures are generally the result of water infiltration related the climatic conditions.
Geophysical methods can help to identify where significant geologic hazards exist or are likely to exist so that informed land use and emergency response planning decisions can be made. These decisions will reduce or mitigate the dangers to life, property and public safety resulting from such hazards.
The benefits flowing from application of geophysics may be direct, as immediate cost reductions, or indirect in the form of an enhanced ore recovery, optimised blasting pattern, or early warning of a safety hazard.