Earthquakes set up surface shock waves which lead to vertical and horizontal shifts and acceleration. Whereas a building can absorb vertical forces relatively well, horizontal forces cause additional stresses.

Because of its homogenous structure, YTONG can even absorb the tensile and compressive stresses resulting from earthquakes along the length of the block. Masonry must be executed with thin-bed mortar, in order to fully exploit YTONG's positive characteristics.

How Earthquakes Originate

Earthquakes are tremors which are triggered by processes in the earth's crust. This sets up a focus such as shear failure. The earthquake then spreads due to tectonic tensions, mostly along a pre-existent fault.

We can define three phases of such a fracture along a vertical vault. The tension that was built up in the first phase can lead – years, decades, or even centuries later – to a significant deformation of both neighbouring plates. If the two plates cannot glide enenly along their boundary (the eventual fault) because they are interlocked in excessive deformation may cause the plates to suddenly rebound. The result is an earthquake.

A cross-section through a focal area reveals a sloping breaking plane and sediment layers above. The earthquake's point of origin is known as the hypocenter, whereas the point on the earh�s surface directly above it is known as the epicentre.

The waves penetrated at the hypocenter travel as seismic waves through the earth�s interior and along- its surface. The area where the waves are felt is called the shocking region. The shock waves are felt with equal intensity on the lines (isoseismals) drawn on a schematic diagram.

If a breaking plane lies just a few kilometres beneath a settlement, considerable damage can arise in a narrowly limited area. If the focus lies deeper, however, an earthquake of the same force will affect a larger area but will cause less local damage.

Earthquake Scales

Scales have been developed in order to be able to describe and compare an earthquake's power and the effect it has on structures. The most commonly used are the magnitude scale (Richter scale) and the intensity scales.

The force of an earthquake is characterised by its magnitude M on the “open-ended” logarithmic Richter Scale. The magnitude is derived from the maximum tremors measured during the earthquake. This, in turn, permits conclusions about the energy set free in the focal point (hypocenter) of the earthquake. Each increase in magnitude of ne unit such as from M=4 to M=5 signifies a thirty-fold increase in earthquake power.

An increase in magnitude is accompanied by an increase in duration. An earthquake with a magnitude of over 8, such as the one that hit Mexico City on the 19th of September 1985, with a magnitude of 8,1, can entail a phase of intense tremors of over 30 seconds.
Since the Richter-magnitude only provides information about the energy set free in an earthquake, it is still necessary to determine the possible damage to a building in such an event. The intensity scales in the ensuing discussion will do that. It is not possible to make a correlation between the Richter magnitude scale and intensity scales because there are a multitude of geological factors at work. In addition, the depth of focal point h and the distance to the epicentre exert great influence of intensity l.
An earthquake has only one single magnitude M on the Richter scale but will have different intensities from place to place, which diminish with increasing distance from the epicentre.

Countries in Earthquake Zones have building codes that address the various problems posed by earthquakes. The actual stresses placed on a structure will depend on the seismic activity (heavy or light) and will depend very heavily on geological conditions. That is why each country has its own numerical values.

Autoclaved Aerated Concrete is extremely strong and durable despite its light weight.

YTONG's solidity, which comes from the calcium silicate that encloses its millions of air pores and from the process of curing in a pressurised steam chamber, an autoclave. Its excellent mechanical properties make it the construction material of choice for earthquake zones.

The product's light weight ensures that the foundations of a building are lightly loaded, yet it is strong enough to bear several floors. It retains its properties for the entire life of a building without ageing. YTONG resists wind, rain, snow and storm and does not decay or rot.

In general, changing outside temperatures cannot damage YTONG Blocks.

Its very limited shrinkage and thermal expansion prevent the formation of cracks in masonry.

Click here to download the research document on earthquake resistant designs using YTONG. This study was made from the National Technical University of Athens for YTONG (pdf).