An Unsurprising Surprise

Like Sumatra in 2004, the power of the Tohoku earthquake in 2011 took us by surprise. Questions naturally arise: After decades of scientific research, how well or how badly are we doing in understanding subduction earthquakes? Are all subduction zones capable of producing magnitude 9 earthquakes? With instrumental records so much shorter than typical recurrence intervals of great earthquakes, can we hope to understand the full earthquake cycle? With comparative studies of different subduction zones, I will show that we have made great progress in understanding subduction earthquakes. In retrospect, the Tohoku earthquake and its tsunami are consistent with such understanding. This understanding is of great value in preparing the society for future, similar events in other subduction zones such as Cascadia.