Tectonic Hazards
Natural disasters result from natural processes that have occurred throughout the history of the Earth. Tectonic hazards arise when the Earth’s crust moves. For example, friction can cause them to get stuck when the plates are moving. Climate hazards occur when specific weather conditions exist in a region; for example, heavy rains can lead to flooding. Hazards can have economic, social, and environmental consequences. The risks or likelihood of specific implications for each hazardous event vary significantly.
Difficulties to Assess Risk in Terms of Tectonic Hazards
Many factors hamper short-term forecasting of mass movement events. Slope destabilization events require constant attention. Mass displacement hazards from volcanic eruptions can be predicted with the same degree of confidence as volcanic eruptions. Still, again, the threat must be recognized, and warning signs must be taken into account. Hydrological conditions: heavy precipitation can be forecast with some confidence, and warnings can be issued for areas susceptible to mass movement processes caused by such conditions (Earthquakes: tectonics, hazard and risk mitigation, 2017, p.205). However, it is difficult to say precisely which hillside out of the millions in existence will be vulnerable to an event caused by, for example, heavy rain.
The Concept of Resilience
Resilience is the ability to absorb or avoid damage without total failure and is the goal of designing, maintaining, and rehabilitating buildings, infrastructure, and communities. A complete definition is the ability to respond, absorb and adapt, and recover in the event of a disruptive event. It is expected that a robust structure/system/community will be able to withstand an extreme event with minimal damage and disruption of functionality during the event; after the event, it must be able to quickly restore its functionality, similar to or even better than the level before the event.
The Social and Economic Impacts of Tectonic Hazards
The consequences of earthquakes are hazardous. If the primary factors of destruction during earthquakes can practically be attributed only to sharp shocks and vibrations of the Earth’s surface, then the secondary characteristics are very diverse. Conventionally, they can be divided into natural and related to human activities. The consequences of human activity include damage and destruction of buildings, fires, explosions, emissions of harmful substances, transport accidents, and failure of life support systems. Floods, including catastrophic ones, are possible due to a breakthrough in hydraulic engineering and water supply structures. Injuries and deaths of people occur mainly due to damage caused by debris from destroyed buildings, structures, structures, and falling objects, as well as being in the rubble and the lack of timely assistance (Siccardi, 2013, p. 94). The annual damage from earthquakes is 7 billion dollars.
Mass Movement Hazards: Slope Stability, Role of Gravity, and Role of Water
The main force responsible for the movement of the mass is gravity. On a flat surface, gravity acts downward. As long as the material remains on a flat surface, it will not move under the force of gravity. Gravity can be divided into two components on a slope: one component acting perpendicular to the slope and one acting tangential to the slope. Forces that prevent movement downhill are grouped under the term shear strength, including frictional resistance and adhesion between the particles that make up the object. When the net stress becomes more significant than the combination of forces holding the thing on the slope, the object will move down the slope.
Although water is not always involved as a transport medium in mass movement, it still plays an important role. Adding water from rain or snowmelt increases the weight of the slope. Water can seep into soil or rock and replace the air in pore spaces or fissures. Since water is heavier than air, this fact increases the total weight of the ground. The weight is force, and force is stress divided by area, so stress increases, leading to slope instability. Water has the property of changing the angle of repose (the angle of repose, which is the stable angle for the slope). Adsorption causes the electron-polar water molecule to attach to the surface of minerals. Absorption causes minerals to accept water molecules into their structure.
Triggering Events Related to Potential Mass Movement Event
A mass movement event can occur at any time when the slope becomes unstable. As in the case of creep or solifluction, the slope is unstable, and the process is continuous (Nelson, 2018, p.3). Minor shocks, such as heavy trucks speeding down the road, trees swaying in the wind, or artificial explosions, can also trigger mass movement. Human or natural modification of a slope can change the angle of the slope so that it is no longer at the angle of repose. The mass movement can then restore the angle of repose of the slope. Changes in the system of groundwater can increase or decrease the total fluid pressure in the rock and cause mass movements.
Mass Movement Hazard Predictions: Understanding of Slope Stability and Triggering Events
All slopes are subject to the dangers of mass movement in a triggering event. Thus, all slopes must be assessed for the potential threat of mass movement. Mass movements can sometimes be avoided by using engineering methods to make the slope more stable. Steep slopes can be covered or sprinkled with concrete covered with wire mesh to prevent rockfalls. Retaining walls can be built to stabilize the slope. If the slope is composed of highly fractured rock, anchor bolts can be installed to hold the slope together and prevent collapse. Drainage pipes can be inserted into the slope to facilitate the exit of water and avoid the increase in fluid pressure, the possibility of liquefaction, or weight gain due to the addition of water. In these cases, people should avoid these areas or use them for purposes that will not increase the susceptibility of life or property to mass displacement threats.
Thus, predicting the risk of tectonic catastrophes is complicated by many factors. Every year, such natural disasters lead to severe economic and social consequences. However, considering the trigger factors, slope stability, the influence of water, and gravity, some phenomena can be predicted. The study of risk factors will make it possible to launch the warning system in time and avoid human casualties, and in the future, possibly, reduce the economic consequences.
References
Nelson S.A. (2018). Natural disasters & assessing hazards and risk. Tulane University.
Siccardi F., Nemec J., Nigg J.M. (2013). Prediction and perception of natural hazards. Germany: Springer Netherlands.
Taher Zouaghi. (ed.) (2017). Earthquakes: tectonics, hazard and risk mitigation. Croatia: IntechOpen.