Seismology

A new study carried out on the floor of Pacific Ocean provides the most detailed view yet of how the earth’s mantle flows beneath the ocean’s tectonic plates. The findings, published in the journal Nature, appear to upend a common belief that the strongest deformation in the mantle is controlled by large-scale movement of the plates. Instead, the highest resolution imaging yet reveals smaller-scale processes at work that have more powerful effects.

Over the last six years, seismologists Göran Ekström and Colin Stark have been perfecting a technique for picking out the seismic signature of large landslides from the stream of seismic data from earthquakes and other activity around the world. The details they are able to extract could one day help governments sound tsunami warnings, help rescuers find landslide-struck villages faster, and warn of risks such as landslide-dammed rivers that could soon burst through.

A new study in the journal Geology is the latest to tie a string of unusual earthquakes, in this case, in central Oklahoma, to the injection of wastewater deep underground. Researchers now say that the magnitude 5.7 earthquake near Prague, Okla., on Nov. 6, 2011, may also be the largest ever linked to wastewater injection. Felt as far away as Milwaukee, more than 800 miles away, the quake—the biggest ever recorded in Oklahoma--destroyed 14 homes, buckled a federal highway and left two people injured. Small earthquakes continue to be recorded in the area.

This spring, a Swedish scientist sparked international concern with a journal article saying that radioactive particles detected in 2010 showed North Korea had set off at least two small nuclear blasts--possibly in experiments designed to boost the yields of much larger bombs. Shortly after, the pot was stirred with separate claims that some intelligence agencies suspected the detonations were done in cooperation with Iran. Now, a new paper says the tests likely never took place—or that if they did, they were too tiny to have any military significance. The new report, by seismologists at Columbia University’s Lamont-Doherty Earth Observatory, will be published later this month in the journal Science & Global Security, where the earlier paper also appeared.

Dr. John Ertle “Jack” Oliver, a geophysicist whose research helped revolutionize our understanding of the basic forces shaping the planet, died peacefully at his home in Ithaca, N.Y., on Wednesday, Jan. 5, 2011. He was 87.

This week U.S. and Haitian scientists will start a 20-day research cruise off Haiti to address urgent questions about the workings of the great Jan. 12 earthquake, and the possibility of continuing threats. They hope to gather sonar images, sediments and other evidence from the seafloor that might reveal hidden structures...

That rumbling you feel is not necessarily a passing subway. New York City and the surrounding region gets a surprising number of small earthquakes, and a 2008 study from the region’s network of seismographs, run by Lamont-Doherty Earth Observatory, suggests that the risk of a damaging one is not negligible. This week, the federal government announced a major upgrade to that network.

Indian Point Nuclear Power Plant Seen As Particular Risk

A study by a group of prominent seismologists suggests that a pattern of subtle but active faults makes the risk of earthquakes to the New York City area much greater than formerly believed.

Seismologists at Columbia University and Harvard University have found a new indicator that the Earth is warming: "glacial earthquakes" caused when the rivers of ice lurch unexpectedly and produce temblors as strong as magnitude 5.1 on the moment-magnitude scale, which is similar to the Richter scale. Glacial earthquakes in Greenland, the researchers found, are most common in July and August, and have more than doubled in number since 2002.

Finding the epicenter of earthquakes has not changed in principle since the 1930s -- after closely examining seismograms from different widely-spaced listening stations, researchers decide on the arrival times of various seismic waves and calculate an approximation. In practice this can result in errors of several miles