qgis - Moving points onto lines (~neighborhood)

I do have two vector layer, of which one is a point layer based on "events" by remote sensing and the second one is a line layer from local research.

In my case these are earthquakes and tectonic faults, but I guess one could simply choose "car-accidents and roads" as a general example.

So what I'd like to do is move/copy the points onto the closest point of the lines, as long as its within a tolerance distance (say 1-2km or 0.0xx°), with the new point layer (+attr moved y/n).

Any ideas ?

Linux, QGIS 1.8