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We're all living in the global aftershock zone

Can a large earthquake trigger another quake hundreds or even thousands of kilometers away? The answer, scientists say, appears to be yes, but when it happens is far from predictable. How does such dynamic triggering affect global earthquake hazards? Perhaps the whole world should be considered an aftershock zone.

19 Oct 2014

Remote triggering of ice quakes

On Feb. 27, 2010, a magnitude-8.8 earthquake struck the subduction zone off the coast of Chile. The resulting Rayleigh surface waves rippled around the world, triggering small earthquakes in many different tectonic settings, including Antarctica. As the surface waves moved across the white continent, a third of Antarctic seismic stations reported shaking coming from so-called “ice quakes.”

19 Oct 2014

Triggered tremor along the San Andreas Fault

The San Andreas Fault (SAF) in California is one of the most active in the U.S., but the 1,300-kilometer-long strike-slip fault seems to only be susceptible to small-scale dynamic triggering. After the magnitude-9 Tohoku quake in Japan in 2011, the SAF experienced an elevated incidence of tremor up and down its length. The tiny tremors were recorded at depths between 16 and 30 kilometers, below the fault’s seismogenic zone.

19 Oct 2014

Casting a seismic shadow

In the week or two before the magnitude-8.6 Indian Ocean earthquake in 2012, Earth was unusually quiet, with few large quakes over magnitude 5. Afterward, seismic activity all over the globe was elevated for more than a week. Then, suddenly, global seismicity dropped off precipitously: Beginning two weeks after the mainshock, no earthquakes of magnitude-6.5 or greater occurred for 95 days.

19 Oct 2014

Santiaguito Volcano's clockwork behavior provides an exceptional laboratory

If Earth breathes, Santiaguito Volcano in the Western Highlands of Guatemala could be its mouth. Roughly every half hour, like volcanic clockwork, Santiaguito’s active Caliente lava dome expands, filling with gas from depressurizing magma below. Then it exhales, often explosively, and deflates. Over the course of a day, you could almost keep time by it.

28 Sep 2014

Virtual water: Tracking the unseen water in goods and resources

Trading in “virtual water” — rainfall and irrigation water used in the production of food commodities or other goods and services, but that isn’t part of the final product — between water-rich and water-poor regions has been suggested as a means to allay water scarcity. And recently, the virtual water concept has gained a foothold among a number of governments and multinational businesses, potentially shaping approaches to water sustainability in the future.

21 Sep 2014

Searching the stars

Thanks to its dry climate and soaring peaks, the Tucson region offers some of the best night-sky viewing in the world.

15 Sep 2014

Getting there and getting around in Tucson

Both Phoenix and Tucson are good arrival points for exploring southeastern Arizona, but it’s best to base yourself in Tucson to visit the attractions described here. You will need a car to get around the area; if you choose to fly in, you can rent a vehicle at either city’s airport. Tucson is located about 180 kilometers south of Phoenix on Interstate 10.

15 Sep 2014

Travels in Geology: Winter sun and tectonic tales in Tucson

Late last March, seeking warm sun and a verdant landscape after a cold, snowy Colorado winter, our family headed south during the spring school break to the lowest-elevation place we could easily drive to in a day or two: Tucson. Hosting Saguaro National Park, the Arizona-Sonora Desert Museum and the largest concentration of astronomical observatories in the country, Tucson has the grand vistas, great hikes and learning opportunities we wanted.
 

15 Sep 2014

Living in the shadow of Mauna Loa: A silent summit belies a volcano's forgotten fury

After 30 years, no one is quite sure when Hawaii’s Mauna Loa will erupt again. History warns us that the volcano’s current silence is anomalous, and the odds are good that it will reawaken within the next couple of decades. So geologists are already taking steps — upgrading their monitoring tools and talking with the public — to prepare for another eruption.

01 Sep 2014

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