what type of wave caused by an earhquake does the most above-ground damage??

Answer 1

surface waves do the most damage above ground.

Answer 2

EQ waves are divided into two types: S and P waves. S waves are transverse, like ripples on a pond. P waves are compressive, like sound waves. Both types can do a lot of damage when they reach the surface with sufficient energy.

Which type "does the most above-ground damage" depends on the structure's vulnerability to each type. Long, flat structures, for example, tend to be less vulnerable to S waves than P waves. This is especially true of long, flat buildings with sufficient expansion joints in their frames.

Tall, thin structures tend to be less vulnerable to P waves than S waves. As an S wave passes under a foundation, it literally tips the tall structure one way and then back the other way. That motion whips the structure back and forth, a motion that is intensified the higher up one goes in the building. (From experience, it is not fun to be on the 40th floor in even a mild Richter 4 earthquake.)

There are all kinds of factors that can change those tendencies however. For example, if the tall, thin structure is resting on a so-called floating foundation, the whipping motion started by an S wave would be absorbed by the foundation and the structure would simply sway back and forth gently without coming apart.

There are similar things one can do the mitigate P wave damage as well. For example, the same floating foundations are usually built on hydraulic or spring-like compression absorbing devices. Both S and P types are absorbed by these multi purpose foundations.

Another factor in determining vulnerability to EQ's is the soil type the structure is sitting on. Rock, for example, tends to heave under P waves equally over the area of the quake. Thus, buildings will be lifted upward as one. As long as the upward motion is relatively even over the area of the foundations, the buildings will probably stay intact. (Things inside will get tossed around however if they are not fastened down.) When the energies reach above 7 Richter, however, all bets are off because very little can be done to make a structure strong enough to withstand that kind of energy.

On the other hand, structures sitting on land fill are at great risk from P waves. (And from S waves, too, for that matter.) This extreme vulnerability stems from liquifaction, where the land fill turns to the consistency of pudding when shook violently in any direction. Thus, any support a foundation might have had from the land fill disappears; the foundation, and the building with it, collapses as it sinks into the pudding.

Finally, there is the tsunami...a series of huge waves is created by the upheaval and collapse of a major area of the ocean floor. Upheaval is caused mainly by a P wave. But the destructive force (the tsunami) comes as transverse waves of ocean water crashing ashore. So, its a bit of a stretch, but one could say S waves cause the most damage by tsunamis. In this case, the S waves are water, not earth, waves.

One word of clarification...on some notable occasions, like the 1906 San Francisco EQ, the major damage was caused by fire...not by the ground shaking.

Answer 3

A slip strike will cause the most damage to the ground and to buildings.

Here is a picture of what a slip strike motion can do..
http://www.geo.uib.no/seismo/quakes_world/Izmit-earthq/damage/golcuk-damage1.jpg

Answer 4

there are 3 types of earthquake waves p, s, and l waves. the l-waves or surface waves are the most destructive.