Seismic on EARTH Magazine

Earthquakes make volcanoes more — and less — gassy

Thu, 10 Aug 2017 11:30:57 -0400

Turrialba Volcano in Costa Rica showed an increase in sulfur dioxide emissions after earthquakes. Credit: ©iStockphoto.com/piratedub.

Triggering of volcanic emissions by earthquakes has been observed since antiquity. The Roman naturalist and philosopher Pliny the Elder proposed the link as early as A.D. 77, and in “The Voyage of the Beagle,” Charles Darwin wrote about inland eruptions in Chile closely following an offshore earthquake in 1835. More recent statistical studies show that after large earthquakes, volcanic activity around the world increases. But the lack of robust monitoring equipment at most volcanoes has made it hard to quantify the relationship. In a new study, scientists demonstrate how satellites can be used to track changes in sulfur dioxide emissions from volcanoes after seismic events, offering a potential way to study the often elusive link between seismicity and volcanism.

Seismic friction causes fault iridescence

Mon, 06 Oct 2014 09:58:56 -0400

Geologist Mitch Prante examines thin hematite layers on a fault surface that recorded ancient seismicity in the Wasatch Fault Zone in Utah. Credit: Jim Evans.

Although iridescent spots on rocks in Utah’s Wasatch Fault Zone were first recognized two decades ago, scientists haven’t understood their origin, until now. New research shows that the iridescence appears on fault surfaces subjected to flash heating from friction and that the spots can provide clues to ancient seismic events.

Creeping faults warn of impending earthquakes?

Thu, 05 Jan 2012 06:41:58 -0500

San Andreas Fault U.S. Geological Survey (USGS): photographer Robert E. Wallace, USGS.

Researchers drilled the San Andreas Fault and extracted core samples that are now being studied. John I. Garver, National Science Foundation

Studying the San Andreas Fault, Fenglin Niu and colleagues recently found a way to help determine that an earthquake is coming. Fenglin Niu

Earthquakes strike out of nowhere — one minute everything is perfectly calm, and the next minute, the ground shakes violently and buildings crumple. However, many seemingly sudden seismic events are actually preceded by a multitude of creeping changes underground. Detecting and interpreting these changes would help forecast earthquakes, but that detection has proven difficult, partly because scientists don’t yet fully understand the complex chain of events that precipitates a quake. Now a team of researchers may have discovered some hidden clues that may help them identify impending quakes.

Don't forget about the Christchurch earthquake: Lessons learned from disaster

Thu, 05 Jan 2012 06:41:58 -0500

The Oxford Terrace Baptist Church was damaged in the Christchurch earthquake. Schwede66, Creative Commons Attribution-ShareAlike 3.0 Unported

In the aftermath of the devastating magnitude-9.0 earthquake and tsunami that struck the Tohoku region of Japan on March 11, attention quickly turned away from a much smaller, but also highly destructive earthquake that struck the city of Christchurch, New Zealand, just a few weeks earlier, on Feb. 22. Both events are stark reminders of human vulnerability to natural disasters and provide a harsh reality check: Even technologically advanced countries with modern building codes are not immune from earthquake disasters. The Christchurch earthquake carried an additional message: Urban devastation can be triggered even by moderate-sized earthquakes.

Glacier moves in fits and starts

Thu, 05 Jan 2012 06:41:58 -0500

Researchers install the seismographs in Antarctica at detected seismic waves from the Whillans Ice Stream. Douglas Wiens

The Whillans Ice Stream — an Antarctic glacier that covers an area slightly smaller than the state of New Jersey — flows from the interior of the continent to the ocean at a rate of about one meter per day. That’s not unusual for a large glacier, but how it covers that distance is surprising. Instead of inching along at a steady pace as most glaciers do, the Whillans Ice Stream jerks forward just twice a day, each time sending out seismic waves equivalent to a major earthquake. Now scientists say they know why — a “sticky spot” under the ice causes the glacier to stall for a while and then suddenly slip.

Japan's megaquake and killer tsunami: How did this happen?

Thu, 05 Jan 2012 06:41:58 -0500

On March 11, 2011, at 2:46 p.m. local time, a magnitude-9.0 earthquake ruptured a 500-kilometer-long fault zone off the northeast coast of Japan. Its epicenter was 130 kilometers off Sendai, Honshu; it occurred at a relatively shallow depth of 32 kilometers. The temblor violently shook northeast Honshu for six minutes, and collapsed its coastline by one meter. The thrusting moved Honshu about 2.4 meters eastward, and the seismic waves on the Pacific Ocean floor set off tsunami waves traveling at the speed of a jet plane (about 700 kilometers per hour). Waves 3 to 38 meters tall pounded Honshu’s coastline, destroying towns and villages and flooding areas up to 10 kilometers inland. Tsunami waves also swept across the Pacific, causing damage or disruptions in Hawaii, California, Oregon, Washington and British Columbia.