UC Irvine researchers have discovered new ways to look at earthquakes and your front lawn. No, not how shakers rip up your green playground. We're talking one study that dispels notions about how experts estimate the potential for the next so-called “Big One,” and a second that disproves the idea that urban “green” spaces—think residential lawns, grassy parkways and parks themselves—help counteract greenhouse gas emissions.
Lisa Grant Ludwig, associate professor of public health at UCI, led a research team composed of Anteaters and Sun Devils (Arizona State University) that established the age of a few dry stream channels with bends created by the San Andreas fault in the Carrizo Plain near Bakersfield. The team then determined how many earthquakes had occurred after the formation of each channel and approximately how much the fault had moved in each quake.
“The distance that a fault 'slips,' or moves, during a large earthquake reveals a lot about the mechanics of faults,” Ludwig says in a UCI.edu feature by Tom Vasich of University Communications. “Getting slip measurements from past earthquakes is like getting a look under the hood of a car—it tells you a lot about the engine.”
Looking under the hood revealed something unexpected: Fault slip varied from earthquake to earthquake instead of recurring in a uniform manner, as had been believed.
“The idea of slips repeating in characteristic ways is very appealing, because if you can figure that out, you're on your way to forecasting earthquakes with some reasonable confidence,” Ludwig says in the piece. “But these results show that we don't understand the San Andreas fault as well as we thought we did.”
Results of the study, to be published online Jan. 21 at Science Express, show the amount of slip that has built up along the San Andreas fault in the Carrizo Plain matches that of the last “big one” to strike there in 1857, suggesting a similarly large earthquake could be coming to the region.
You're welcome, Carrizo Plainers!
“The recent disaster in Haiti is a reminder that a destructive quake can strike without warning,” Ludwig says. “One thing that hasn't changed is the importance of preparedness and earthquake-resistant infrastructure in seismically active areas around the globe.”
Earth system science postdoctoral researcher Amy Townsend-Small's study, which is to be published in the journal Geophysical Research Letters, finds total greenhouse gas emissions would decrease—in Southern California, at least—if lawns did not exist here at all.
Yes, turfgrass lawns do help remove carbon dioxide from the atmosphere through photosynthesis and store it as organic carbon in soil, making them important "carbon sinks.” What, you think we're stupid?
What Townsend-Small discovered was maintaining those grassways requires fertilizer production, mowing, leaf blowing and other lawn management practices that emit four times more carbon than what is stored. And nitrous oxide, which is released from soil after fertilization, is a greenhouse gas that is 300 times more powerful than carbon dioxide.
"Lawns look great—they're nice and green and healthy, and they're photosynthesizing a lot of organic carbon. But the carbon-storing benefits of lawns are counteracted by fuel consumption,” Townsend-Small says in a second UCI.edu feature, this one by Jennifer Fitzenberger of University Communications.
Townsend-Small says the results of her research are important to greenhouse gas legislation being negotiated.
"We need this kind of carbon accounting to help reduce global warming,” she says in the article. "The current trend is to count the carbon sinks and forget about the greenhouse gas emissions, but it clearly isn't enough.”
Townsend-Small and colleague Claudia Czimczik analyzed grass in four parks near Irvine to come up with the findings. The study was supported by the Kearney Foundation of Soil Science and the U.S. Department of Agriculture.