Why are houses built on swamp automatically considerd unsafe for earthquake?

[Vivaldi]

Building I live around were made in early 90s. The area was swamp.

In 1999, 7.4 magnitude earthquake happened. And those buildings were so close to the center of Earthquake.

Nothing happened to those buildings. Buildings didn't even get damaged.

They proved how much they were earth quake resistant.

[genericname85]

i don't think that fact makes your house any more or any less resistant to earthquakes, given that the swamp was dried properly. mayb the buildings were just well built.

at the point where there's a floating effect to such a degree that it dampens an earth quake, that would also effect the long term stability of houses. the heavier parts would sink and make the house crack or even just straight up collapse over the years.

[Vivaldi]

Why do you mean? Buidings not even having a damage in 7.4 Magntitude Earthquake doesn't make them Earthquake resistent?

[genericname85]

well no. i'm saying that IF the swamp was the reason for thier earthquake resistence, the effect of building on a swamp would mean that these house are earthquake resistant for now but will not be long term stable.

[Vivaldi]

I didn't mean that. I meant why they would be automatically considered unsafe for earthquake for this reason. That is what I mean.

[genericname85]

well for the reason i already explained. either that swamp was properly dried up and then it's not much different than any ground to build on.
and if it wasn't properly dried, these houses would slowly sink at their heaviest part and crack/collapse sooner than houses built on regular ground.

[genericname85]

so like it would make these houses less structurally sound in general.

[Vivaldi]

Tunnel Formwork System and Rat foundation were used in the buildings.

[Vivaldi]

Raft

[genericname85]

well that doesn't matter if the walls are sinking into the ground.

[Vivaldi]

As I said, at 7.4 magnitude earthquake in 1999 here, buildings didn't even have a damage.

[Vivaldi]

Nothing happened. No Damage.

[Vivaldi]

Nothing except shaking happened.