The Northwest coastal area of North American is part of the Pacific Rim where tectonic plates jostle against each other and create volcanos and earthquakes. There are hundreds of earthquakes a year in these parts, most of them too small to cause damage and only detectable by sensitive equipment. Swarms of earthquakes come and go and what might that mean?
The "big one" has happened on average every 300 years or so. The last big one here, based on geological evidence here and tsunami records in Japan, was in the late 1600s—about 350 years ago.
This larger format book is both a good overview and a wealth of detailed information. Lots of charts and photos. Fascinating and more than a little worrisome. Much of our expanding city (including the international airport) is built on vulnerable landfill that is likely to liquify during an earthquake.
The next big one could be tomorrow or in 100 years. Who knows? The "art" of predicting earthquakes is like forecasting the weather, except much much less accurate.
If you live in Northwest and you're looking for a book to make you nervous about your earthquake insurance policy, this is it. Packed with scientific details about historical quakes and tsunamis as well as detailed maps of where the fault lines are in the Northwest (yay! one runs under my house!) and their seismic potential. Lots of great info on seismic hazards, tsunamis and what you can do to prepare for them - a fantastic read albeit one which will have you ordering earthquake straps for your furniture after you finish it.