Please note: I am not a licensed geologist, and I have no definite opinion on the proximate or ultimate causes of this landslide and its damages. Many factors, from the reservoir's presence to specific building practices to local drainage to vegetation management, may have a bearing on what happened. I prefer the fuzzy disclaimer of Haines, in James Joyce's Ulysses, that "it seems history is to blame."
But the signs of landslide activity are not difficult to learn, and there are resources beyond those I used. For instance, the city library may have a historical collection, and the local "friends of the creek" (in this case, the Friends of Sausal Creek) may have special insights. Real-estate agents cannot know everything—you have to do your own due diligence.