Earthquace Science

When the earth shook here on March 26th 2000, it helped geologists to figure out how the earth around Seattle would shake during the real thing less than a year later. When Seattle’s Kingdome was demolished with explosives, more than 200 seismic recorders caught every rattle and roll. Tom Brocher of the U.S. Geological Survey says: "You can see the red waves travelling away from the Kingdome." The areas that shook the worst then also shook the worst when the 6 point eight (on the Richter scale) Nisqually earthquake hit. "We shouldn’t be surprised to see damage at Boeing field and at the port of Seattle where we did see damage, because in both of those areas the ground shook longer and harder than other parts of Seattle." It’s what’s known as a slab quake (located) 36 miles below the surface where the Juan de Fuca plate slab is diving underneath the North American plate. Geologists believe the plate bent, causing it to crack, sending shock waves to the surface. Tom Brocher says, "As soon as we knew it was a deep earthquake- that it was this type of earthquake- we immediately put out the word that we should expect very few aftershocks." There were only 4. In San Francisco's Loma Prieta earthquake here in 1989 which was closer to the surface, there were 120 aftershocks. The fact that "deep-focus" earthquakes have fewer aftershocks still puzzles geologists. Brocher says, "What we can tell people is you’re not going to have these (aftershocks). What we can’t tell them why. And that’s a research issue." Geologists say the Nisqually quake originated from almost the same spot as the 1949 quake there, and had the same damage patterns. There were fewer landslides this year because of the lack of rain. Over the next year and half, researchers want to set off explosives at the surface near Seattle. Aimed at the slab 37 miles below. The waves will then bounce off the slab and reflect back to the surface giving information about where the plate is and how it’s moving. So, before