I was in the 89′ San Francisco quake. I was 3 stories up in a building when it hit. I saw the same ripple you did except I was looking out the window and it was the whole ground that was doing it. It boggles the mind to see something you consider so solid rippling like liquid. It was terrifying and awesome all at the same time. There are a few different lines of thought on what to do in an earthquake. One I found interesting is called the triangle of life. I can’t remember the guy’s name that wrote it. I will see if I can find it. His point was to get next to something large and sturdy not under it. If there is a collapse the object may get crushed but will create small triangles of space right next to it. If you are under the object you get crushed but if you are next to it you may very well wind up in one of those triangle spaces. I will see if I can find the article. It was very interesting.