Only Yamuna is supposed to have moved East with the tectonic movement raising the divide between the Indus catchment area and the Ganges catchment area. As for Sutlej, it meanders in a plain and has changed its course many a times in history. Sites of late Harappan culture exist even in east of Yamuna (see the Post-Harappan image in my post # 408). People, then moved further East along the river Ganges clearing the forests and settling down as they went on.
The line going across the image is the disappeared Sarasvati River mentioned in Vedas. It has the maximum Indus Valley sites. Perhaps at one time, Sutlej and Yamuna, both large rivers, joined it making it the most important river in the area. Due to tectonic movement, Sutlej joined Indus and Yamuna joined Ganges, thereby obliterating Sarasvati. That is the area which is supposed to have got raised around 1,900 BCE. Earthquakes are common in Himalayan region. Kalibangan (larger even than Mohenjodaro and Harappa), Ganerwali, Alamgirpur are important Indus Valley sites.