Understanding the difference in earthquake codes for apartment buildings

Buyers often ask us about earthquake codes. For a country that lies alongside the Pacific Ring of Fire, it is a risk that we should all be aware of.

The most recent major change to the Building Standards Act for earthquake resistance occurred in 1981.

Why is this important?

You may often see buildings referred to as Kyu-taishin and Shin-taishin. Kyu-taishin refers to buildings that were built to the former earthquake codes in effect up until May 31, 1981, while Shin-taishin refers to buildings that meet the latest codes introduced on June 1, 1981. 

The former Kyu-taishin code stipulated that a building be designed to withstand and not collapse in an earthquake producing a seismic intensity (Shindo-scale) of upper 5, although some damage may be sustained. However, no standards were outlined in the event of a larger earthquake that produced a seismic intensity of 6 or higher.

The Shin-taishin code was introduced after the 1978 Miyagi Earthquake and stipulates that for the often occurring mid-sized earthquakes (magnitude 5 ~ 7), the building should suffer only more than a slight amount of cracks and should continue to function as normal. For the rare and large earthquakes with a magnitude of 7 or higher and a Shindo scale of upper 6 or higher, the building should not collapse.  

*It is important to note that the seismic intensity scale (Shindo) does not refer to magnitude.

If a building was completed after June 1, 1981, is it going to meet the latest earthquake codes?

Not necessarily.

The important date to take note of is not the completion date but rather the date that the application for building approval was submitted. If it was prior to June 1, 1981, it is possible that the building was built to the former earthquake codes.

Buildings take time to be constructed, especially larger ones. Even a building built in late 1982 might not necessarily be built to the newest codes if construction started prior to the code revision.

Are all buildings prior to this date going to be riskier than newer ones?

Not in all cases. There may have been some developers and builders may have built older buildings to even higher standards than were required at the time. A proper earthquake-resistance inspection can determine a building’s strength.

However, as real estate brokers we personally cannot determine the structural strength of a building, and cannot provide any guarantees or certainty of the safety of an older structure (or even a newer one for that matter). We can only go by the date of the building approval application to identify if a building is classified as Kyu-taishin or Shin-taishin.

Only a certified structural engineering company can do the required earthquake-resistance analysis of a building. That can often require drilling into a structure and other invasive procedures. For a condo-type apartment building, this work requires the approval of the owners association. Some owners associations may have already carried out this inspection, but not all. For a buyer of a single apartment in a multi-dwelling building, you will not receive approval to do this on your own, and certainly not prior to purchase.

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