Geophysical hazards may be further classified in to geological and geomorphological hazards. These are split by their energy source. Some are driven by the Earth’s internal energy, e.g. volcanoes, earthquakes, tsunamis, and others are driven by land surface processes, e.g. landslides and avalanches. Climatological and meteorological hazards are driven by the sun’s energy, e.g. tornadoes, hurricanes, and drought. More recently, hazards have become exacerbated by human actions. These are known as quasi-natural hazards.

Hazards are also classified by magnitude and frequency. Magnitude is the ‘size’ of a hazard, and represents the amount of geophysical work done. Many hazards have their own specific magnitude scales, e.g. Richter scale (earthquakes), Saffir-Simpson scale (hurricanes), volcanic explosivity index (volcanoes) and the TORRO scale (tornadoes).
Sometimes, hazards are classified by the duration of the impact and warning time. Sudden impact hazards are judged by damage, whereas slow onset hazards are harder to judge in this way. Hazards may be classified by spatial distribution of impact and occurrence. Some hazards are associated with distinct regions, e.g. volcanoes and plate boundaries.

Risk
Risk is defined as the exposure of people to a hazardous event. People consciously place themselves at risk from natural hazards. Factors explaining this were identified by Park (1992);
(i)    Unpredictability - hazards are not predictable, and people may be caught out by either the timing or magnitude of an event.
(ii)  Lack of alternatives - people may stay in a hazardous area due to a lack of options. This may be for economic reasons linked to their jobs, are because of a lack of space or lack of employment skills or knowledge.
(iii) Dynamic hazards - the threat from hazards is not a constant one, and it may increase or decrease over time. The human influence may change the location or increase the frequency or magnitude of hazardous events.
(iv) Cost versus benefits - the resources or benefits of a hazardous location may well outweigh the risks involved in staying there.
(v)  Fatalism - the acceptance of the risks as something which will happen whatever you do. Belief in Fate, or God’s will is typical of this. Also known as ‘Russian roulette’ reaction.

Vulnerability
The impact and scale of a hazardous event is largely determined by human factors. Just as people benefit differently from the resources available, so there are differences in how they are prone to the risks. Recent Californian earthquakes caused large amounts of economic loss, but an Armenian earthquake of the similar magnitude caused 25 000 deaths. In the 1995 Kobe earthquake in Japan, the older and poorer members of society were the worst hit. The richest people suffered less damage, and could move away from the area in a short space of time. Thus vulnerability refers not only to the event, but to the ability to recover afterwards.

It seems that there are a variety of factors which influence the degree of vulnerability
(a)  Wealth and level of technical ability can affect the degree to which protection can be built, e.g. building resistant homes, or utilising the latest software and technology to design and construct preventative measures, or predict impacts. Poorer people cannot afford to protect themselves to the same degree.
(b)  Education is important; in particular with reference to the level of awareness of hazards and what protection can be taken. Practice in emergency procedure is also a key method of minimising the loss of life. All children in Japan are trained in earthquake and fire drill four times a year. Government properties and companies observe Disaster Prevention Day annually on 1^st September, which marks the anniversary of the Tokyo earthquake.
(c)  Organisation levels are also important. Group effort, either at local/national government level can prepare themselves better, and organise relief efforts afterwards more effectively.

Health and vulnerability are related to age. Disasters affect the old or very young to a disproportionate degree. These groups are weaker in health terms. People’s resilience depends upon their income and social class, as these affect their ability to absorb the losses incurred. But vulnerability is not necessarily the same as poverty.

It is the increasing vulnerability of people which accounts for the increased impact over recent years. As population increases, the number of people living in hazardous areas also increases. The higher population and rates of increase in the LEDCs increase their vulnerability relative to the MEDCs. The vulnerable range from the poorest countries, e.g. Bangladesh or Ethiopia, where human cost is high, but economic cost is low, to the MEDCs like Japan or the USA, where fatalities are low but the economic cost is high. In between are the rapid growth countries which may experience both high human and economic losses.

Modifying people’s vulnerability is an important aspect of hazard management, along with approaches which centre on the hazardous event. Tackling the economic aspects of vulnerability is complex and long term, while focusing on self and social protection at a local or regional scale is more effective and more realistic.

Hazard perception
We react to hazards in different ways, because of the difference in the way in which we process and filter the information we receive. Warnings of risk involve people going through the stages which shape their perceptions and behaviour, i.e. hear, confirm, understand, believe, personalise, respond. Each stage is affected by age, gender, and level of education, the nature of the information and the repetition of the warning. The perception of hazards can be divided in to three groups, which may overlap and include elements of more than one view;

(a)  Acceptance; include fatalistic tendencies. Hazards are natural events which are a part of life, or result from ‘acts of God’. Events are random, and we can only respond for safety. Our actions are intuitive, and losses must be accepted.
(b)  Domination; Hazards are extreme events. They are predictable, and their magnitude can be forecast. We can understand them better by scientific research. Control is possible through engineering or use of technology.
(c)  Adaptation; Natural hazards will happen, and are influenced by human and natural events. Their magnitude and frequency may be guessed based on experience. There is a need to adjust, respond flexibly and research. We must look at both human and physical systems in our responses.

Human Responses to Hazards
People respond to hazards and the treats to human life and possessions in a way designed to reduce risk. The response can be at a variety of levels, e.g. local, regional, national, and the response chosen will depend upon the nature of the hazard, past experience, economic ability to take action, technological resources, hazard perceptions of the decision makers, knowledge of the available options and the infrastructure of the political system.

Not all of the available options may be taken, since resources and time may be required. The importance of the threat from the natural hazards relative to other factors, e.g. employment, healthcare, education will influence any decisions. People and governments must be willing and able to invest in hazard impact reduction. This is known as hazard salience.

Responses to hazards can be divided in to three groups;
(a)  Prevent or modify the event; these management strategies aim to control the physical process involved by the technological fix, and therefore, modify and prevent the hazardous event, in one of two ways;
·       Hazard prevention and environmental control. Ideally, the event would be prevented from occurring. This is currently unrealistic. Environmental control aims to suppress the event by diffusing energy over a greater area or period of time to prevent the event occurring. Floods may be diverted by a wide range of engineering structures, e.g. dams, levees, channel changes or afforestation. Control of atmospheric processes, such as cloud seeding with silver iodide to end droughts tend to be largely unsuccessful.
·       Hazard resistant design; aims to protect people and structures from the full effects of the hazard. The focus is on the building design and engineered solutions, e.g. sea walls. Buildings can be designed to withstand hazards, and most public structures, e.g. roads, dams, bridges, will have some hazard resistant features incorporated.

(b)  Modify vulnerability; this aims to change human attitudes and behaviour towards the behaviour towards hazards, either before the event, or after it.
·       Prediction and warning. If a hazard is predicted, action can be taken to lessen its impact on people and property. Insurance companies spend large amounts of money in order to adjust their premiums to cover losses. Between 1970 and 1995, 28 of 30 of Lloyd’s most expensive losses were natural disasters. Hurricane Andrew in 1992 resulted in $16 billion in claims. Companies can thus set higher premiums in higher risk areas. Warnings inform people of impending hazards. They rely on adequate monitoring and evaluation of the data, then the effective dissemination of the information via various information services.
·       Community preparedness; This involves prearranged measures and procedures which aim to reduce the loss of life and minimise damage. This includes such measures as public education and awareness programmes, evacuation procedures and provision of emergency shelters, food and medical supplies. Effective use of this has saved many lives over the years, including in the Rabaul volcanic eruption in 1994, where a emergency plan was successfully implemented to save thousands.
·       Land use planning; which aims to prevent hazardous areas being occupied by new settlements. Problem is that is cannot be applied to new areas. Success depends on accurate knowledge of frequency, nature, and location of hazards.

(c)  Modify the loss; the most passive response is to simply accept the losses incurred. This is rarely acceptable, especially after higher magnitude events. More commonly, the strategy is to share the losses. This can be acheived in two ways; aid and insurance.
·       Aid is provided at many levels for relief, rehabilitation and reconstruction purposes. High magnitude events are often declared disaster areas, and the losses shared nationally. At the international level, politics and pride often interfere with aid being asked for or given. In such situations, the United Nations is often involved, or charitable non governmental organisations, e.g. the Red Cross are involved in aid. Often, sudden disasters generate more aid donations than slow onset hazards, such as droughts.
·       Insurance is a key strategy in the MEDCs. The principle is that people join with a financial organisation to spread costs. An individual needs to act by purchasing a policy, and paying an annual premium. Insurance companies need to identify key areas of risk and hazards in order to secure their business. In 1994, Californian insurance companies collected $500 million in premium payments, but paid out $11.4 billion in claims resulting from the Northridge quake. Insurance for high risk area may not be available, or come with stipulated conditions, e.g. buildings must have certain construction techniques employed. It encourages people to take preventative measures for themselves.

CASE STUDIES:Case Study for Vulnerability; Costa Rica, Central America.

Key data; GNP per capita US $2160. 1994 trade deficit, US $810 million. There are 1179 people per doctor, and 35% of the population are under 15. 49.7% of the population live in urban areas.

Costa Rica is at risk from multiple hazards. The local climate can result in alternate extremes of flooding and drought, and the country is prone to hurricanes. Geomorphological hazards includes landslides and storm surges. An increase of disasters in recent years has been linked to global warming and climatic change, but also deforestation and degradation at the local scale. Its vulnerability can be grouped under simple headings;

(a)     Economic Vulnerability; Costa Rica has a large national debt, a negative GNP per capita growth, and 28% of the population in poverty. 54% of families have an income level equivalent to the minimum wage [1990] of $145 per month. Most homes are structurally unprotected, with only 1% of homes built to any seismic specification, both public and private.

(b)     Social Vulnerability; Fatalism is a common belief. 27% believe hazards to be a product of nature, and 11% the punishment or will of God. People see hazards as beyond their control (externalisation), both in terms of the event, and the aftermath. There is no incentive to work to form local groups. This fatalist belief is mainly due to religious factors, and the prioritisation of other factors, e.g. income and employment.

(c)     Educational/informational vulnerability; There are few emergency education programmes, and most of these relate to seismic and volcanic hazards, as opposed to flooding. Early warning systems fail because of the widespread area of impact, the large number of small communities involved and the lack of economic resources. Information is not community specific.

(d)     Environmental vulnerability; deforestation and poor land management can increase he risk of flooding, landslides, and avalanches. Urbanisation of slopes and hilltops increases runoff and the vulnerability of lower communities. It is likely to be the poor who occupy the higher risk land.

Case Study for Insurance Management; California, USA.
California has a high risk of earthquakes. Yet less than 50% of its residents have insurance other than the state legal requirement. Earthquake insurance has been available in California since 1916, and since 1984 has been an option of general contents insurance.  The cost of earthquake insurance is relatively high, especially in terms of excess, which may be as much as 10% of the value of the house. Following the Lomo Prieta earthquake of 1989, the state government has stepped in to provide mandatory insurance of up to $15 000, mainly to cover insurance losses. The national government levies a surcharge on all residential insurance policies, which goes in to an emergency fund.

Five factors have been determined as important in the purchase of earthquake insurance;
(a)     Resources; the money, intellectual skills and time to consider, select and adopt effective mitigation measures.
(b)     Perception; two opposing cultures. The belief in technology solutions absolves the individual of responsibility. Opposed to this is the American culture that individuals are responsible for their own well being.
(c)     Risk; Individuals calculate the probabilities that a given hazard will affect them. This may differ from the scientific view.
(d)     Time; dependent upon length of residency in the area, residents may take a long term or short term view. The time frame involved in the decision affects a person’s response.
(e)     Hazard salience; the relative importance of a hazard compared with other concerns, e.g. employment, family and career.

Summary
A natural hazard is an event which has the potential to cause loss of life or property damage. Hazards are a key interaction between humans and the physical environment. They may be classified by cause, magnitude and frequency, duration of impact and warning and spatial distribution.
Risk is the exposure of people to a hazard. Hazard impacts have increased as a result of increasing numbers of people being placed at risk.
Vulnerability to hazards has three aspects; preparedness, resilience and health, related to social, economic, and political factors. Perception of hazards varies, and includes acceptance, domination and adaptation.
Human response can also take three forms; modify the event by control and design, modify vulnerability by prediction and warning, and modify the loss by aid and insurance. The choice of response is related to the nature of the hazard, past experience, economic and technological resources, socio-political conditions and hazard perception.