Does the vulnerability of a community determine whether a tectonic hazard will become a disaster?
The term vulnerability can be interpreted in many different ways. The United States Agency for International Development [USAID] defines vulnerability as “the characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard” (2011: 11). In order to understand the vulnerability of a population in a natural hazard event, comparisons can be made between multiple communities that have faced the same or similar hazards. Through these comparisons it makes it possible to assess if one community is more prone to a disaster than another. Whether a natural hazard develops into a natural disaster is determined by multiple factors, including: the magnitude of the hazard event, the vulnerability of a community, and a community’s capacity to cope with the hazard event. The interactions between these factors can be demonstrated through the hazard-risk equation:
Disaster risk (R)= (Hazard (H) x Vulnerability (V))/(Capacity to cope (C))
(USAID, 2011)
The equation therefore demonstrates the importance of vulnerability in determining if a natural hazard will develop into a natural disaster.
Vulnerability
Location is an important factor to consider when evaluating vulnerability; populations that are distant from a hazard face little threat in comparison to populations living in close proximity to the hazard. Plymouth, the capital of Montserrat, sat at the base of the Soufrière Hills volcano when it erupted in 1995. As a result, 3,006 people were highly vulnerable as they lived with 5km of the volcano (Global Volcanism Program, 2013a). Plymouth was destroyed and several locals were killed, causing major disruption to the island. In contrast, the area around the Shiveluch volcano in Russia is largely uninhabited. Shiveluch is described as one of the largest and most active volcanoes with the most violent eruptions in the Kamchatka peninsula (Volcano Discovery, n.d.). However, as no one lives within 10km of the volcano (Global Volcanism Program, 2013b) the area is not vulnerable as there is no direct threat to human life. Consequently, location places a key role in determining a community’s vulnerability and therefore the development of a tectonic disaster.
However, vulnerability incorporates a number of different factors; the demographics of an area can determine how quickly an evacuation can occur. Communities with a high proportion of children and babies can be considered vulnerable due to their dependency; they do not have the ability or strength to escape the hazard or understand it (Guha-Sapir et al., 2006). Similarly, elderly populations are also vulnerable. They are likely to have a number of health problems and are often weaker, making it difficult for them to evacuate and remove themselves from the area of risk. Japan’s 2011 Töhoku tsunami highlights the importance of demographics. Japan has an aging population due to the decline in birth rates, however the distribution of the young and the elderly is not even. As a result, coastal regions have a high proportion of elderly people while urban cities have a high proportion of young adults. This has caused Anderson (2011) to suggest that the impact of the tsunami was “demographically biased against the elderly”. Consequently, it can be inferred that elderly people are more vulnerable to tectonic events, such as tsunamis, than young adults as it is difficult for them to move away from the hazard.
Furthermore, populations can be vulnerable on a larger scale; the way in which a country is governed can determine not only vulnerability, but the country’s capacity to cope. Well governed nations often have a high capacity to cope and a low vulnerability, while poorly governed nations that have been mismanaged are often the most vulnerable. Countries such as Haiti have been corrupt in the past, leading to mismanagement of the economy through the borrowing of loans with substantial interest. Poor governance has consequently impoverished the nation, resulting in little construction of viable infrastructure, and creating a highly vulnerable society with very little capacity to cope with hazard events (Oliver-Smith, 2010). Corruption can therefore influence the development level of a nation.
Development levels influence both a nations vulnerability and capacity to cope; high income countries are often less vulnerable than low income countries and are more able to cope with hazard events. High income countries are able to invest into new technologies and mitigation techniques that reduce the risk, while low income countries do not have the funds to do so. Nepal is a low income country that is vulnerable to earthquakes and landslides. In 2015 a magnitude 7.8 earthquake occurred in Nepal. As the majority of buildings were not made with ductile material, many structures failed, resulting in numerous fatalities (Goda et al., 2015). In contrast, New Zealand is a high income country that frequently experiences tectonic activity. In an attempt to reduce the number of fatalities that result from the collapse of buildings, New Zealand has invested in technologies to develop earthquake resistant buildings. These technologies aim to make buildings more ductile and able to dissipate seismic wave energy (Mercer, 2016). As a developed high income country, New Zealand has the funds to reduce the vulnerability of its citizens. Developing countries with low income, such as Nepal, are often unable to invest in such technologies and so remain vulnerable to tectonic hazards.
Management
Not only does the vulnerability of a community determine whether a hazard becomes a disaster, but the overall management and response to the hazard can have a have a huge impact. By having management procedures in place an has an increased capacity to cope with the event. As previously mentioned, countries such as New Zealand are investing in technologies to make buildings more ductile during earthquakes. One method of making buildings more ductile is to add bracing, allowing the buildings to withstand greater lateral loads (Seismic resilience, n.d.). This dissipates seismic energy, reducing the likelihood of structural failure and therefore the number of fatalities. Similarly, methods used to manage tsunamis also aim to dissipate energy. However, this is achieved in a different way. Mangroves are a type of vegetation found in tropical and subtropical zones along the coast. Through dissipating wave energy, mangroves are able to act as a defence against tsunamis as they reduce the power of the waves (Alongi, 2008). By adopting various technologies a hazard event can be well managed, resulting in a reduced vulnerability and a greater capacity to cope.
Although implementing these modifications help to manage a hazard event, monitoring the hazard itself enables populations to move out of harm’s way or have greater time to prepare. The importance of monitoring tsunamis was highlighted after the 2004 Indian Ocean tsunami. On the 26th December 2004 a magnitude 9.1 megathrust earthquake occurred off of the coast of Sumatra, Indonesia resulting in tsunami waves of up to 30m (Rodgers and Fletcher, 2014). As a result, tsunami early warning systems were implemented in numerous oceans, including the Indian Ocean, in order to prevent a disaster of that magnitude form occurring again. The tsunami warning messages are typically received 5 minutes after an earthquake, allowing time for the data to be interpreted and for citizens to evacuate the area (Satake, 2014). Early warning systems are consequently a clear demonstration of how disasters can be avoided by strong management, saving thousands of lives.
Furthermore, by working with developed nations, low income countries are able to prevent a hazard from becoming a disaster; these alliances allow poorer nations to have access to high-tech monitoring systems and prepare for a hazard event. Before 1992 Mount Pinatubo eruption in the Philippines, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and the U.S. Geological Survey (USGS) joined together to study and monitor the volcano’s activity (de Guzman, n.d.). Although numerous citizens died in the eruption, the event had the power to kill many more people but was prevented from doing so by the joint efforts of the Philippines and the USA. By having access to sophisticated technology, the volcanologists and seismologists were able to evacuate everyone living within 20km of the volcano (Pinatubo Volcano Observatory Team, 1991). Development levels are important in determining whether a hazard will become a disaster however, the events in the Philippines demonstrate that even a low income country can reduce the impact of a hazard through effective management.
The Hazard
Despite a community having low vulnerability, effective management and a large capacity to cope, occasionally the hazard itself has a magnitude so large that a disaster is created in spite of this. The damage a hazard can have is determined by its physical properties and the magnitude of the event. The magma type plays a key a role in determining explosivity of a volcanic eruption. Magma types involve different types of igneous rock including: basalt, andesite, dacite, and rhyolite. Mafic magma is associated with basalt rock. The magma has a silica content of 50%, a low gas content, a low viscosity, and has a temperature of between 1000°C and 2000°C (National Geographic Society, 2018). As a result, the magma is fluid and is non-explosive. Andesite is associated with intermediate magma. It has a silica content of roughly 60% and has a higher gas content and viscosity than mafic magma. The temperature of the magma ranges from 800°C to 1000°C and eruptions tend to be violent (National Geographic Society, 2018). Furthermore, dacite and rhyolite are associated with felsic magma. Felsic magma the highest silica content at 65-70%. It also has the highest gas content and viscosity, and the lowest temperatures of between 650°C and 800°C. Consequently, felsic magma produces the most explosive and destructive eruptions (National Geographic Society, 2018). Disasters may therefore be created due to the type of magma in the volcano; basaltic eruptions pose less threat compared to rhyolitic eruptions.
Similarly, the type of seismic waves can determine whether a disaster will be created due to an earthquake. There are two types of body waves: P-waves and S-waves. S-waves travel more slowly than P-waves, however unlike P-waves they are unable to be transmitted through liquids. Additionally, there are two types of surface waves: Love and Rayleigh. Love waves move in a horizontal motion while Rayleigh waves are transmitted in an elliptical motion similar that of waves in the ocean (Smith, 2001). Love and Rayleigh surface waves move more slowly than body-waves. The slower a seismic wave travels the more destructive it is. Therefore, earthquakes are more likely to develop into a disaster when surface waves are transmitted.
Consequently, both the type of magma and the type of seismic wave can determine the magnitude of a hazard event; the higher the magnitude the more likely the event will become a disaster. The eruption of Mount St. Helens in 1980 can be considered a disaster due to its Volcanic Explosivity Index (VEI). The VEI is a scale that ranks the size of an eruption by the volume of material ejected. The 1980 Mount St. Helens eruption had a VEI of 5, which categorises the eruption as very large (U.S. Geological Survey, 1997). Due to the magnitude of the eruption there were 57 fatalities occurred including volcanologist David Johnston. As Mount St. Helens is located in Washington State, USA, the event demonstrates that developed countries cannot always avoid disasters. This could also be seen in the 2011 Töhoku tsunami. On March 2011 a mega earthquake occurred. The earthquake had a magnitude of 9.0, causing severe damages in addition to a tsunami (Takano, 2011). Despite Japan’s infrastructure being designed to withstand such events, they were easily overpowered.