March 12, 2014
Tohoku tsunami maps: lessons for the Pacific Northwest
Posted by Austin Elliott
As we pass the three-year mark since one of the most astoundingly gargantuan earthquakes in human history, we marvel at the unprecedented opportunity it gave us to understand earthquakes, tsunamis, oceanic subduction, litho-hydro-atmospheric coupling, plate tectonics, and the Earth itself. We can also appreciate, with humble reverence, the lessons it continues to teach us about the social dimensions of disaster trauma, risk, and resilience. Japan continues to struggle, now largely far outside the glow of the media spotlight, to rebuild entire counties that were literally wiped away, and to support a traumatized and devastated citizenry.
Meanwhile the global scientific community continues to learn from the best recorded earthquake to have ever struck the modern world–a title the Tohoku-Oki quake will likely hold for generations due to its rare magnitude and exceptionally well instrumented epicenter. The three videos below show just what modern instrumentation and computing power afford us. The first two show animations of real-time GPS data that recorded the whole country lurching eastward during the quake. The last is a buoy-data-constrained model of the tsunami as it encircled the Pacific Ocean. All three are marvelous illustrations of the Earth’s power, and of what contemporary data collection can show us.
In the months and years following the earthquake, crafty visualization of the extraordinary event became the best way to grasp just how extreme it was. I compiled a bunch of these visualizations and sonifications in a prior post, and they’re definitely worth revisiting on this anniversary:
The other extraordinary artifact of this earthquake was the preponderance of first-hand video footage of the quake in action. The ~4+ minute long earthquake and ensuing 40-meter-high tsunami were both such absolutely unimaginable events that most video of them defies belief. In all likelihood it will serve as the most important and most durable evidence of just how extreme these Great subduction zone earthquakes can be. The 9th century Japanese had carved stones; we had YouTube.
Many scientists have drawn the important parallel between northeastern Japan’s tectonic situation and the U.S. Pacific Northwest’s Cascadia subduction zone. With the semicentennial of North America’s largest earthquake right around the corner, and Tohoku fresh in our heads, it’s an apt time to take stock of how modern mainland U.S. will fare in the inevitable monster quake that will strike offshore Oregon and Washington.
Officials have been taking the risk seriously and beefing up the PacNW’s emergency plans. The most illuminating way to draw analogy between 3/11 and the next big PacNW quake (the last one was in 1700) is through comparison of these great online maps:
Great Maps of Earthquake Effects
The first one is a remarkably thorough compilation of geographic data and measurements from Tohoku. The map has everything: seismicity, shaking intensity, infrastructure damage, tsunami inundation maps and measurements, nuclear fallout maps, and so on and so forth. It’s an amazing suite of data products all easily toggled and overlaid.
Compare that to this map from Nanoos Visualization Systems, produced in conjunction with the Oregon Department of Geology and Mineral Industries and the Washington Department of Natural Resources, which shows tsunami evacuation zones, routes, and safe gathering places along the U.S.’s entire Pacific Northwest coast.
As you click around coastal Oregon remember that what happened in Japan three years ago happened in Oregon three centuries ago, and will continue to recur throughout the state’s future, including truly any day.
How far inland can average tsunamis that have been devastating get?
Most tsunamis are not devastating. Scientists can and do measure tsunamis which are as small as a few centimeters. These events rarely make the news. The tsunamis which are ‘devastating’ are the very largest (and rarest) ones. What I think you really…