The goal of risk assessment is to determine the probability of a tsunami striking an area, and the magnitude of damage that occurs. Damage can be described in three areas: human life, property destruction, and destruction of land. We would recommend that the destruction of property (such as buildings and roads) and the destruction of land (rainforests, farmland) be measured in the dollars required to restore it to its original state.
HOW TO ASSES RISK:
The first step in assessing the risk of a certain area is to determine its location relative to a fault line. Then the nature of the fault line should be classified as the type of fault line that generally causes tsunamis, like a subduction zone, or the type that does not like sea floor spreading. (UNESCO) Areas that are closer to subduction zone faults will be considered to have a higher risk setting than those that are farther away, or close to faults that are not subduction zones. The next level of risk assessment takes into account the bathymetry in between the fault and the area being assessed. (Bascom) If the seafloor there is conducive to large waves, by being flat and gradually sloping for example, then the area would have an increased risk state (Bascom) than an area that is protected by many coral reefs or berms. (Pennisi) The next thing to be considered is the topography of the area. If the area is flat, low lying, or even below sea level as opposed to an area that has bluffs on the oceans edge, or just steeply rising hills close to the ocean (Yalciner) so there is at least somewhere for the populace to go in case of a tsunami then it will be considered to be more dangerous to live there. An easy way to determine this is to make inundation maps based on elevation. For example, if a wave hit a city and all areas that were below 8m would be affected then it is easier to inform all the people in that area that they are of a higher risk due to the elevation at which they live. A final consideration in judging the risk of an area is the environment surrounding it. If there are mangroves or heavy vegetation between the area and the ocean where the wave would hit then the area would be of lower risk than if the shoreline had be deforested and there was no protection or buffer zone to dissipate the strength of the wave. Once the risk of a tsunami affecting a certain area, and the magnitude of the impact, it can then be determined the damage that the area will incur. If the area has a high population density then it will be considered at higher risk than an area that is very rural, just because the chance for casualties is greatly increased. Furthermore, if an area¡¯s buildings are poorly designed then the chance of destruction is greater, but if a place¡¯s buildings are well designed but more expensive the risk of associated with expensive property loss increases. A final indicator of the risk of damage is the ecosystem of the area. The potential for damage to an ecosystem can be related to the how long it will take for the ecosystem to be functional again, if there are any species that will greatly suffer or may even become extinct, and the amount of vegetation that needs to be replaced in order to maintain a healthy balance.
Looking at the data for tsunami history in the past 100 years, one can assess the risk of the probability of tsunamis impacting a certain area. To supplement this, (or if there aren¡¯t any records of tsunamis) one can look at the history of earthquakes and their magnitudes in the past 100 years and assess the probability of a tsunami with that data. Most major earthquakes occur along subduction zones and most significant tsunamis are caused by earthquakes of magnitude 6 or higher. An algorithm can be created that considers the tsunamis occurring in the pacific ocean over the past 100 years and earthquakes that have been over magnitude 6 or greater. Major subduction zones near Micronesia and Peru are the Mariana trench (between the Philippines and Pacific Plate) which have an average of 18 earthquakes per year. Another one is the Peru-Chile trench and the Tonga Trench.
ASSESSING THE RISK FOR PERU AND MICRONESIA:
In order to asses the risk for Peru and Micronesia we will be using primarily maps created in the GIS lab. The first map is labeled with the fault lines near Peru and Micronesia, and the fault lines that are subduction zones are be highlighted in order to identify areas that are closer to it, and to determine the areas along the coastline¡¯s relative risk.
The second map shows the inundation based on the elevation of the areas. There is a gradient that shows how much of the area will be submerged when there is a certain amount of water that comes from the wave.
The next map has the population density on it so the areas that have a higher population density, like cities and urban areas, can be marked as having a higher risk if they already fall into high risk zones.
The final map will have all of the previous maps combined into one map that highlights the regions with the most relative risk along the coastline of both Peru and Micronesia.
Bascom, Willard. Waves and Beaches. New York City: Doubleday, 1964.
Pennisi, Elizabeth. "Powerful Tsunami's Impact on Coral Reefs Was Hit and Miss." Science 4 Feb. 2005: 657. MIT. 20 Sept. 2005.
Yalciner, Ahmet C., Efim N. Pelinovsky, Emile Okal, and Costas E. Synolakis. Submarine Landslides and Tsunamis. Boston: Kluwer Academic, 2003.