Collapsing buildings = Major cause of death.

During an earthquake, what causes loss of life? We think it would be useful to verify our assumption that collapsing buildings/ falling rubble is a major cause of death and/or injury. Detailed below is some of the research which we have found online.


Here is a useful excerpt from http://science.jrank.org/pages/2224/Earthquake-Collapse-buildings.html :



"To construct a house or building under static conditions, the materials need only to be stacked up, attached to each other, and balanced. These kinds of buildings are not designed to accelerate rapidly and change directions like cars or airplanes. Buildings in seismically active areas, however, must be designed and built to withstand the dynamic acceleration that can occur during an earthquake. Large buildings and structures such as bridges, in particular, must be designed so that vibrations arising from earthquakes are damped and not amplified.
Because noticeable earthquakes are rare in most areas, people may not recognize that the objects and buildings around them represent potential hazards. It is not movement of the ground surface alone that kills people. Instead, deaths from earthquakes result from the collapse of buildings and falling objects in them, fires, and tsunamis. The type of construction that causes the most fatal injuries in earthquakes is unreinforced brick, stone, or concrete buildings that tend not to be flexible and to collapse when shaken.
The most earthquake-resistant type of home is a low wooden structure that is anchored to its foundation and sheathed with thick plywood. Some of the traditional architecture of Japan approximates this shock-resistant design, including wooden buildings that are more than a thousand years old. Unfortunately, wood and paper houses can be easily ignited in the fires that are common after large earthquakes. Both unreinforced masonry and shock-resistant wood houses are used by different cultures in areas of high earthquake risk."



Here is another excerpt, from http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/earthquake_effects.html :

"The first step in preparing structures for shaking is to understand how buildings respond to ground motions- this is the field of study for earthquake and structural engineers. When the ground shakes, buildings respond to the accelerations transmitted from the ground through the structure's foundation. The inertia of the building (it wants to stay at rest) can cause shearing of the structure which can concentrate stresses on the weak walls or joints in the structure resulting in failure or perhaps total collapse. The type of shaking and the frequency of shaking depends on the structure. Tall buildings tend to amplify the motions of longer period motions when compared with small buildings. Each structure has a resonance frequency that is characteristic of the building. Predicting the precise behavior of buildings is complicated, a rule of thumb is that the period of resonance is about equal to 0.1 times the number of stories in the structure. Thus Macelwane Hall resonates at about 0.3 seconds period, and Griesedeck at about 1.4 seconds. Taller buildings also tend to shake longer than short buildings, which can make them relatively more susceptible to damage. Fortunately many tall buildings are constructed to withstand strong winds and some precautions have been taken to reduce their tendency to shake. And they can be made resistant to earthquake vibrations. In many regions of limited resources and/or old structures, the structures are not very well suited to earthquake induced strains and collapse of adobe-style construction has caused thousands of deaths in the last decade. The worst possible structure for earthquake regions is the unreinforced masonry (which is common in the St. Louis area)."

Here is a third useful source, "SEISMIC VULNERABILITY AND COLLAPSE PROBABILITY ASSESSMENT 

OF BUILDINGS IN GREECE", from the Second International Workshop on Disaster Casualties in  June 2009, http://pager.world-housing.net/wp-content/uploads/2009/06/Pomonis_Antonios.pdf :

"The PAGER methodology therefore aims to rapidly  estimate human casualties from earthquakes based on the fact that most earthquake fatalities around the globe are linked to the collapse of buildings (Allen et al., 2009). A study into the causes of death from earthquakes in the period 1900-1999 (1.6 million victims worldwide) estimated that approximately 70-75% of lives were lost due to building collapse, while the remaining 25-30% due to other causes such as, tsunami, landslides and fire following the seismic event (Spence, 2003). This continues to be the case to this day despite the 2004 Indian Ocean tsunami which killed 228,000 people, because an additional 240,000 building-collapse-related deaths took place in the 2000-2008 period, bringing the total life loss in the 1900-2008 period to nearly 2.15 million people (assuming that the loss of life in the 1976 Tangshan earthquake is as officially reported (243,000) instead of unofficial estimates of as many as 655,000 deaths)."