I liked the photo that one of the quoted seismologists, Zhigang Peng from Atlanta, supplied to the author of this article - which depicts the seismologist standing in front of a sign marking the San Andreas fault on a visit to California. Its just the kind of photo a visiting seismotourist would take !
Simultaneously with India, also Africa and Arabia have collided with Eurasia.
So the Himalayas have formed at the same time with a great number of mountain ranges, from the Atlas and the Pyrenees at the Western extremity, passing through many other mountains, e.g. the Alps, the Carpathians, the Caucasus, the Hindu Kush, the Pamir etc., until the Himalayas at the Eastern extremity.
See:
https://en.wikipedia.org/wiki/Alpine_orogeny
You don't consider that "tectonic activity"?
It might help to think of it less as "Indian subcontinent slamming in" and more as the "Tethys ocean basin closing".
India being pulled away from Africa/Madagascar and eventually beneath the Eurasian continental crust is all related to the closing of the Tethys. ...This is a lot easier to explain with pictures...
If it helps, remember that continents are just lighter and thicker "rafts" of stuff. They're not plates themselves. They're often attached to oceanic crust as part of a plate. When one side of that oceanic crust becomes cold and thick enough to start to subduct, the entire plate gets pulled along.