Are civil engineers in the United States ignoring the opinions of seismologists and other engineers when it pertains to building in earthquake-prone areas? The Seattle Times definitely thinks so. They have been running a feature of articles called Seismic Neglect, that references decades of engineering research that has indicated building practices in unreinforced masonry construction (URM) occurring in areas that could be hit by earthquakes. Meaning, construction in unreinforced buildings is going ahead despite seismology data that directly indicates the area could see earthquakes topple those constructions.
According to Seattle Times, there are 1,163 unreinforced structures in the Seattle area. These are buildings' that walls are not bolted to the floors or the ceilings and would be hazardous to the area if an earthquake hits. The Seismic Safety Council did caution against the list of buildings built under unreinforced masonry but local governments have been inactive. People are wondering why these buildings have not yet been retrofitted for seismic activity.
The opinion makers say it is a bit disconcerting that there are still unreinforced masonry constructions in an area that lies directly in the Cascadia Subduction Zone area that could experience a megaquake of 9.0 quite soon. Some structures are able to withstand earthquakes - and they have - but a 9.0 magnitude could send these buildings toppling.
You can also read the Federal Emergy Management Agency's (FEMA) report on Unreinforced Masonry Buildings and Earthquakes. The three biggest concerns for FEMA in unreinforced masonry construction are: Injury, Property Damage, and Loss of use [of the building]. The agency suggests a strategy that can be implemented so that risk can be minimized with the unreinforced buildings.
The principal means of reducing the seismic risks of unreinforced masonry buildings is retrofitting, although changing a building's use in order to reduce its occupant load (number of occupants) also reduces risk.
FEMA's suggestions could also help other countries that suffer the same fate of having outdated buildings that are not earthquake-proof. One of the ways a building can be retrofitted for seismic activity is by installing seismic isolation devices, which act as shock absorbers during an earthquake or like Figure 32 where strongbacks can be installed to preserve the strength of the wall so cracks or a collapse do not happen. It really depends on how the building was designed to begin with that factors into what kind of retrofitting is necessary.
What remains clear is that unreinforced masonry constructions need to be listed and worked on by engineers so that buildings all around the world can be retrofitted for earthquake safety, especially in areas which fall under fault lines and known seismic areas.
