# Would a larger building more safely or smoothly ride the seismic waves of an earthquake?

If larger ships are less affected by ocean waves, and tend to ride smoothly through them, would that same principle influence the survivability of a larger building when weathering the seismic waves travelling through the ground?

Note that for the purposes of this question, the building would be assumed to have been strengthened in similar fashion to the lengthy hull of a large ship. The question is really about whether the building could ride the seismicity more smoothly given a larger contact area with the ground waves.

• Let me point out that ships cut through waves except when the wavelength is considerably greater than the hull length. It's not at all the same phenom as a building trying to hold together as the ground it's tied into moves (with rare exception of buildings built on floating pads) Commented Nov 1, 2021 at 16:47
• Further, consider that earthquakes can leave a fissure and/or a residual step-function difference in ground height. Water can do neither. Not to mention that water waves involve travelling height waves, which earthquakes are primarily longitudinal pressure waves. Commented Nov 1, 2021 at 16:48

Earthquake waves are very long. For example in California, the frequency of the 1996 Northridge earthquake was 0.5Hertz.

This shock could cross the diameter of the earth in half an hour (Not correct! it reflects once it hits the core, really a rough estimate).

That translates to a P wavelength of 13 kilometers. S waves are longer but in the same order.

A building has to be in the order of 12 kilometers long to be affected by the tidal effect of the earthquake.

Regardless, if a building is designed for the earthquake using codes its height and length, and geometry, even the irregular mass distribution, or vulnerable geometry has already been considered.

In most instances other than the very basic one or two-story residential building the design has to be based on the dynamic reaction of the building to a simulated earthquake most likely to happen on the site or a simplified but more conservative static design.

If a large ship is hit side on by a huge it can roll over. Ships have better success at surviving large waves by sailing into large waves.

Size of buildings is one factor. How it is built is another and what it is made from also matters. Large steel framed building tend to deal with seismic shocks better than large masonry buildings.

Other factors are the magnitude of the seismic event, they type of seismic waves that hit the building an how the building is orientated to the approaching seismic waves.

The type of foundation the building has and whether soil liquefaction occurs also matters.

Yes. If everything else holds constant, the building with a larger footprint will perform better than the smaller one due to the higher redundancy it possesses.

• This only holds if you posit that the building is more strongly connected to itself (laterally) than each post is connected to the ground. Commented Nov 1, 2021 at 16:45
• @CarlWitthoft I have no clue about your comment as it seems to ignore the fundamental understanding of a building with a higher degree of structural indeterminacy innately possesses higher redundancy, which in turn enables stress redistribution to occur that may prevent the complete collapse mechanism from happening. The base or the lower-level columns always carry the greatest deadweight, unless there is soft-story above, or with some geometric deficiencies, they are the weakest links of the entire building and are typically failing the first, the fewer the columns, the lesser the stability.
– r13
Commented Nov 1, 2021 at 18:03

It all depends on the period of the ground shaking vs building. Long period earthquake waves shake tall buildings more as their periods are longer. The period of the ground shaking vs period of the building should not match.

• I don't think this is a valid analysis Commented Nov 1, 2021 at 16:47
• Can you tell me why? Commented Nov 1, 2021 at 18:52
• I think the counterweight system installed in the Taipei 101 building is a good indication of the importance of tall buildings mitigating seismic moments. Commented Nov 1, 2021 at 21:38
• And what about the other millions of tall buildings which doesn't have counterweight (which is irrelevant to what I said anyway)? Tall buildings have long periods. If the earthquake period is also long, this will be dangerous. Search for the term "resonance" Commented Nov 2, 2021 at 4:33