09/20/2012 16:39:21
Katie Neith
With the help of some tiny worms, researchers at Caltech have gained new insight into the highly complex task of migrating cells.

Peak-2

09/26/2012 16:23:21
Marcus Woo
David Hsieh, an assistant professor of physics, is one of Caltech's newest faculty members. He recently answered a few questions about his work—and some culinary experiments.

Fun Facts

  • The Caltech mascot is the beaver—an homage to nature's engineer.
  • Caltech's founding fathers—astronomer George Ellery Hale, physicist Robert Andrews Millikan, and chemist Arthur Amos Noyes—were nicknamed "Tinker, Thinker, and Stinker."
  • Beginning in 2007, the campus hosted fall olive harvest festivals to collect as much as 2,600 pounds of olives from the trees along the famed Olive Walk. The olives yielded anywhere from 50 to 150 gallons of oil depending on the year.
  • The annual Pumpkin Drop takes place at midnight on Halloween, when students drop pumpkins frozen in liquid nitrogen from the top of Millikan Library to see if they'll give off a brief glow as they hit the ground and shatter.
  • When the Museum of Hoaxes's website published a list of the top 10 college pranks of all time, Caltech was the only school to be listed twice.
  • Each House at Caltech has a fully stocked kitchen. Whether you're craving cereal, fresh fruit, pasta, soup, or ice cream, they've got it all!
  • Millikan Library is one of the most-often-shaken buildings in the world, as Caltech's seismologists use it to test earthquake detectors and to gather other types of seismological data.
  • In 2006, the U.S. Postal Service issued a set of limited-edition stamps featuring photos of snowflakes taken by Caltech physics professor Ken Libbrecht.
  • The cannon outside Fleming House is actually fired a handful of times throughout the year. We won't tell you when; just be prepared!
  • Residents of Blacker House are known as "moles"—named for the unit of measurement, not the underground creatures.
  • Robert Andrews Millikan was Caltech's first Nobel Prize winner, becoming a laureate in 1923.
  • Every morning during finals week, at 7 a.m. on the dot, Richard Wagner's "Ride of the Valkyries" is played at an ear-splitting volume.
  • Rumor has it that the largest In-N-Out burger ever prepared was made for Caltech students.
  • Caltech's motto is "The truth shall make you free."
  • The photocopying technique known as xerography was developed by a Caltech alum in 1938.
  • To celebrate the end of Daylight Savings Time each year, Techers try to pull a negative-time Tommy's run: The goal is to drive downtown, eat a burger at the original Tommy's, and arrive back on campus before they left.
  • The Emmy-nominated television series, The Big Bang Theory, which is set at Caltech, taped an episode on campus that featured a cameo appearance by world-renowned astrophysicist Stephen Hawking.
  • Over the years, the Caltech campus has made cameo appearances in several well-known TV shows and movies, including The X-Files, The West Wing, Legally Blonde, Entourage, and Mission: Impossible, among others.
  • Approved PE classes at Caltech include Ultimate Frisbee, table tennis, and power walking.

An Earthquake in a Maze

The powerful magnitude-8.6 earthquake that shook Sumatra on April 11, 2012, was a seismic standout for many reasons, not the least of which is that it was larger than scientists thought an earthquake of its type—an intraplate strike-slip quake—could ever be. Now, as Caltech researchers report on their findings from the first high-resolution observations of the underwater temblor, they point out that the earthquake was also unusually complex—rupturing along multiple faults that lie at nearly right angles to one another, as though racing through a maze.

The new details provide fresh insights into the possibility of ruptures involving multiple faults occurring elsewhere—something that could be important for earthquake-hazard assessment along California's San Andreas fault, which itself is made up of many different segments and is intersected by a number of other faults at right angles.

Most mega-earthquakes occur at the boundaries between tectonic plates, as one plate sinks beneath another. The 2012 Sumatra earthquake is the largest earthquake ever documented that occurred away from such a boundary—a so-called intraplate quake. It is also the largest that has taken place on a strike-slip fault—the type of fault where the land on either side is pushing horizontally past the other."Our results indicate that the earthquake rupture followed an exceptionally tortuous path, breaking multiple segments of a previously unrecognized network of perpendicular faults," says Jean-Paul Ampuero, an assistant professor of seismology at Caltech and one of the authors of the report, which appears online today in Science Express. "This earthquake provided a rare opportunity to investigate the physics of such extreme events and to probe the mechanical properties of Earth's materials deep beneath the oceans."

[[{"type":"media","view_mode":"full_grid_9","fid":"2243","attributes":{"alt":"","class":"media-image","height":"359","width":"450"}}]]The earthquake happened far offshore, beneath the Indian Ocean, where there are no geophysical monitoring sensors in place. Therefore, the researchers used ground-motion recordings gathered by networks of sensors in Europe and Japan, and an advanced source-imaging technique developed in Caltech's Seismological Laboratory as well as the Tectonics Observatory to piece together a picture of the earthquake's rupture process. 

Lingsen Meng, the paper's lead author and a graduate student in Ampuero's group, explains that technique by comparing it with how, when standing in a room with your eyes closed, you can often still sense when someone speaking is walking across the room. "That's because your ears measure the delays between arriving sounds," Meng says. "Our technique uses a similar idea. We measure the delays between different seismic sensors that are recording the seismic movements at set locations." Researchers can then use that information to determine the location of a rupture at different times during an earthquake. Recent developments of the method are akin to tracking multiple moving speakers in a cocktail party.

Using this technique, the researchers determined that the three-minute-long Sumatra earthquake involved at least three different fault planes, with a rupture propagating in both directions, jumping to a perpendicular fault plane, and then branching to another.

"Based on our previous understanding, you wouldn't predict that the rupture would take these bends, which were almost right angles," says Victor Tsai, an assistant professor of geophysics at Caltech and a coauthor on the new paper. 

The team also determined that the rupture reached unusual depths for this type of earthquake—diving as deep as 60 kilometers in places and delving beneath the Earth's crust into the upper mantle. This is surprising given that, at such depths, pressure and temperature increase, making the rock more ductile and less apt to fail. It has therefore been thought that if a stress were applied to such rocks, they would not react as abruptly as more brittle materials in the crust would. However, given the maze-like rupture pattern of the earthquake, the researchers believe another mechanism might be in play.

"One possible explanation for the complicated rupture is there might have been reduced friction as a result of interactions between water and the deep oceanic rocks," says Tsai. "And," he says, "if there wasn't much friction on these faults, then it's possible that they would slip this way under certain stress conditions."

Adding to the list of the quake's surprising qualities, the researchers pinpointed the rupture to a region of the seafloor where seismologists had previously considered such large earthquakes unlikely based on the geometry of identified faults. When they compared the location they had determined using source-imaging with high-resolution sonar data of the topography of the seafloor, the team found that the earthquake did not involve what they call "the usual suspect faults."

"This part of the oceanic plate has fracture zones and other structures inherited from when the seafloor formed here, over 50 million years ago," says Joann Stock, professor of geology at Caltech and another coauthor on the paper. "However, surprisingly, this earthquake just ruptured across these features, as if the older structure didn't matter at all."

Meng emphasizes that it is important to learn such details from previous earthquakes in order to improve earthquake-hazard assessment. After all, he says, "If other earthquake ruptures are able to go this deep or to connect as many fault segments as this earthquake did, they might also be very large and cause significant damage."

Along with Meng, Ampuero, Tsai, and Stock, additional Caltech coauthors on the paper, "An earthquake in a maze: compressional rupture branching during the April 11 2012 M8.6 Sumatra earthquake," are postdoctoral scholar Zacharie Duputel and graduate student Yingdi Luo. The work was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, and the Southern California Earthquake Center, which is funded by the National Science Foundation and the United States Geological Survey.

 
Subtitle: 
Caltech researchers provide highest-resolution observations yet of the complex 2012 Sumatra earthquake
07/04/2012 07:00:00
Marcus Woo

Maria Spiropulu and Harvey Newman, both professors of physics at Caltech, lead the Caltech team of 40 physicists, students, and engineers that is part of the Compact Muon Solenoid (CMS) collaboration at the Large Hadron Collider (LHC) in Geneva, Switzerland.

07/04/2012 07:00:00
Marcus Woo

Physicists at the Large Hadron Collider (LHC) in Geneva, Switzerland, have discovered a new particle that may be the long-sought Higgs boson, the fundamental particle that is thought to endow elementary particles with mass.

06/28/2012 07:00:00
Katie Neith

Last fall, assistant professor of chemistry Long Cai received a New Innovator Award from the NIH—funding meant to both stimulate highly innovative research and support promising new investigators. Just nine months later, Cai has published the first results of his supported research.

06/13/2012 16:00:00
Marcus Woo

This morning, NASA's NuSTAR telescope was launched into the low-Earth orbit from which it will begin exploring the high-energy X-ray universe to uncover the secrets of black holes, the dense remnants of dead stars, energetic cosmic explosions, and even our very own sun.  

05/24/2012 07:00:00
Allison Benter

Today is Ditch Day! Follow the shenanigans on Flickr, Facebook, and Twitter!

 

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