Securing Bookshelves to the Wall for Earthquakes

This photo shows how we secured some of our bookshelves to the wall for earthquakes. When I visited Hiroshi Kawase at Kyoto University, he showed me a demonstration of a ~6 foot bookshelf toppling in a simulated earthquake on a shake table. It was actually VERY impressive. When the shelf fell, it landed with extreme force. I don't see how anyone receiving the brunt of that fall could escape without very serious injury. So securing bookshelves is important.

What you see here is a 3 inch angle iron. The top of the angle iron is attached to the solid wooden top of the bookshelf, but on the inside. The back side has long screws going through the thin plywood backing and plaster, into a wooden stud in the wall in back.

We had this system in place during the strong shaking we experienced during the Mogul earthquake. All of our shelves remained secure. This one is on the second floor of our house. The Mogul earthquake had a peak vector ground acceleration, recorded in our yard, of 1.19g, but the duration was short because it was only a magnitude Mw=5.0 event. So the lack of long-period energy means that this was not the most severe possible test. Still, the shelf also feels very secure when I try yanking on it, so I think this system is sufficient.