On March 11, 2011, a magnitude (M) 9.0 earthquake occurred approximately 130 km off the east coast of Japan. The earthquake, known as the Tohoku event, was the fourth-largest recorded since the advent of modern seismometry more than 100 years ago. The energy release was equivalent to an M 9.4 event including the subsequent faulting in the following 25 minutes. Along with severe shaking of the island nation, the earthquake triggered a tsunami affecting the entire Pacific Rim. The northeast coast of Japan, the region closest to the epicenter and facing the tsunami propagation direction, suffered the most devastating effects with a wall of water exceeding a height of 10 m in places. In areas of subdued topography, the tsunami raced several kilometers inland before receding, as evidenced by the moderate resolution imaging spec troradiome ter (MODIS) satellite images (Williams, 2011, from http://itworld.com/business).
The impact of the tsunami is readily apparent from the extent of deposited silts and sands that reached several kilometers inland, over almost all the populated regions in the images. Standing water and extensive sediments are seen throughout both cities in the bottom image. Many hundreds of aftershocks, ranging into the mid 7s in magnitude, have occurred and will continue to occur over the better part of the coming year, underscoring the instability of the situation. The purpose of this article is to provide an overview of the spectrum of the natural disaster and its environmental health impact to the human population (White, 2011, from http://www.constructionweekonline.com).
As the Earth is a dynamic planet, the health and well-being of human society have always been susceptible to impacts from natural events. Earthquakes in particular have a long history of significantly impacting societies through direct effects of building collapse and infrastructure damage due to ground shaking and subsequent disasters such as fires and tsunamis. Earthquakes occur wherever stresses build up in the Earth's crust beyond its elastic breaking point. Stresses build relatively quickly at tectonic boundaries where two or more plates come in contact with one another(Shults & Faw, 2008, pp. 103-118).
Geological Setting of Earthquake and Tsunami
The country of Japan sits at the junction of several converging tectonic plates. Notably, the Pacific plate subducts are pushed below northern Honshu along the Japan Trench at a rate of 93 mm/yr., while the Philippine plate subducts beneath southern Honshu along the Nankai trough at a rate of 58 mm/yr. As the plates subduct they tend to lock with the overriding plate, thereby building up tectonic strain. When the strain becomes larger than the strength of the locked fault surface, the fault causes an earthquake. The magnitude of the event depends on both the area of the strain and the amount of slip along the interface. The M 9.0 Tohoku event occurred along the Pacific plate. The fault rupture area was nearly 400 km long and 150 km wide with slip as great as 32 m. A portion of the northeastern Honshu permanently shifted more than 4 m eastward and dropped three-quarters of a meter downwards (Vijayan, 2011, from http: //www.computerworld.com).
The Tohoku earthquake was felt around the world, and three traces of a seismogram recorded at Southern Illinois University in Carb ondale, Illinois, show ground movement in three perpendicular directions. Four distinct arrivals can be observed: Direct P and S along ...