tsunamis

[geordief]

what happens to a tsunami as it bends around a coast?

Suppose it approaches an island from south to north.Does the South bear the brunt of the wave?

Do the effects tend to lessen as the wave flows around the island?

I seem to remember that the West Coast of Sri Lanka was very badly affected even though the wave approached from the East when the Christmas Tsunami struck.

Would that have been down to local conditions magnifying the wave in particular area is the wave as well able to attack from the rear as from the front?

[steevey]

what happens to a tsunami as it bends around a coast?

Suppose it approaches an island from south to north.Does the South bear the brunt of the wave?

Do the effects tend to lessen as the wave flows around the island?

I seem to remember that the West Coast of Sri Lanka was very badly affected even though the wave approached from the East when the Christmas Tsunami struck.

Would that have been down to local conditions magnifying the wave in particular area is the wave as well able to attack from the rear as from the front?

 

What happens is you have something that creates a powerful shock wave, or a sort of solid pillar of water from something like an Earth quake. As the same singular wave approaches the coast, the water it carries gets forced upwards by the fact that the coast is also slanting upwards as it travels along more of the coast. So the shape of the island doesn't really matter, its more of how tall it reaches at the coast and how powerful the shock waves is.

[Kerry]

There's more about tsunamis here - including the Christmas Tsunami

 

Different types of waves occur on either side of the fault. Positive or crest waves – the more dangerous of the two because of their vague warning signs – are caused by the plate on one side of the fault moving upwards. The crest of the wave arrives first, and the sea level rises rapidly, overwhelming everything in its path. When this wave passes, the water recedes quickly as the second wave arrives. In the 2004 tsunami-causing quake, the Burma plate was pushed up, and the waves struck places like Sri Lanka.

 

 

Negative or trough waves are characterised by a rapidly receding sea which is followed by a sudden rush of water at high speed. The drawback occurs because the tectonic plate on one side of the fault sinks suddenly which causes the overlaying water to propagate outwards with the trough at the front. It was a negative wave which hit the island of Phuket in Thailand in 2004.

 

Hope that helps