Cascadia's Fault - Jerry Thompson [92]
The engineers and scientists at PMEL went to work on a new generation of satellite communications technology that would work in both directions and on demand. If a moderate-size earthquake ruptured somewhere under the sea and the seismometers picked up the signal, the on-duty crew at the warning centers ought to be able to send out a signal to wake up the tsunameter buoys and get a reading instantly on all the waves coming across the system—even those slightly below the 1.2-inch (3 cm) threshold.
This way they could spot smaller tsunamis immediately and issue—or cancel—warnings based on real data rather than “an absence of triggered data.” So the PMEL engineering team continued to plug gaps in the existing buoy system. At the same time, Vasily Titov and his colleagues were fine-tuning their tsunami model software so that it could use the incoming data stream to forecast what the waves would do when they finally made landfall.
Eddie Bernard knew that roughly 900,000 people would be at risk from a fifty-foot (15 m) tsunami, which is what the computer models said might happen if Cascadia ripped apart. Inundation maps were being drawn for California, but work on the Oregon and Washington coastlines had barely begun.
The weakness in the system continued to be the strategic location of the detection equipment. Because the deep-ocean buoys were placed far enough out in the Pacific to give western North America and Hawaii plenty of warning for a tsunami from Japan, the sophisticated new technology is too far away to be of use in a local rupture of Cascadia’s fault. The buoys are anchored out beyond the subduction zone, so Cascadia’s waves would hit the beaches of the Pacific Northwest at almost exactly the same moment that the pressure detectors picked up the signal at mid-ocean and sounded the alarm.
Bottom line: if you’re on a beach and the ground starts shaking—and especially if that shaking lasts more than one minute—it’s probably a subduction earthquake and there probably will be a tsunami. The shaking is all the warning you’re going to get. Head for higher ground immediately and don’t wait for any official notification.
Defining Cascadia’s zone gave scientists a more accurate sense of what they were dealing with. Building the prototypes for a deep-ocean tsunami alarm system in the Pacific gave emergency responders a way to make better decisions about whether to evacuate coastal communities when a distant fault ripped and heaved the ocean floor. But the potential for megathrust quakes closer to home remained a subject of debate, and the implications of giant waves generated not far off the West Coast had still not sunk in. An air of unreality and deniability hung over the whole business. It would stay that way until somebody could pin a specific date and magnitude on Cascadia’s last great rupture.
CHAPTER 16
Cracks, Missing Rings, and Native Voices: Closing In on a Killer Quake
Long before Chris Goldfinger sailed the Indian Ocean in search of mud cores from the Sumatra 2004 earthquake, he dropped a fish off the Oregon coast and found Elvis. He and Bruce Applegate, both graduate students at OSU in the late summer of 1989, went to sea in a research ship called Wecoma using side-scan sonar to take state-of-the-art pictures of the ocean floor. The ship towed a chirping metal “fish” at the end of a long cable thousands of feet beneath the sea surface, pinging sound waves off the bottom to create a digital map that looked as realistic as aerial photos showing the terrain of the ocean floor in stunning detail.
Gliding across the wide, flat abyssal plain, the fish kept chirping, sound waves echoed back, and a strange new picture emerged from the deep. In Living with Earthquakes in the Pacific Northwest, Bob Yeats described Goldfinger’s discovery of a fault that had cracked the floor of the sea channel and buckled the sediments into a low hill. The onscreen sonar image looked remarkably like a man