2020-10-15. What Controls Giant Subduction Earthquakes? By Patricia Waldron, Eos/AGU. Excerpt: Subduction zones with a low dipping angle and thick sediments can produce giant earthquakes; this finding lets researchers estimate worst-case scenarios for coastlines around the world. Giant earthquakes—those greater than magnitude 8.5—are rare. …Two of the largest earthquakes (and subsequent tsunamis) ever observed occurred in the past 2 decades, the 2004 Sumatra earthquake and the 2011 Tohoku earthquake. Both had an estimated magnitude of 9.1, which surprised scientists. “No one expected such large earthquakes at those places,” said Sobolev. Influential research dating back to 1980 proposed that earthquake magnitude depended on the age of the subducting plate and the rate of subduction. Specifically, a young oceanic plate with a rapid rate of subduction was estimated to produce the biggest earthquakes. But conditions at the Sumatran and Japanese subduction zones didn’t fit into this classical view. …Now, a new study that models seismic activity in subduction zones has pinpointed the factors responsible for Earth’s largest earthquakes. …Iskander Muldashev, a geophysical modeler at Bremen University, and Stephan Sobolev, a geodynamic modeler at GFZ Helmholtz Centre Potsdam, developed numerical models that simulate seismic cycles for subduction zones [paper]. The models showed that a shallow angle of subduction for the sinking oceanic plate and a thick layer of sediments in the trench where it meets the continental plate were the most important factors in creating a large rupture zone, leading to giant subduction earthquakes…. [https://eos.org/articles/what-controls-giant-subduction-earthquakes]
2020-07-13. Desert quakes may have boosted chances of ‘big one’ striking California. By Roland Pease, Science Magazine. Excerpt: A pair of earthquakes that struck the remote California desert 1 year ago have raised the risk of “the big one” hitting Southern California, according to a new study. The research finds that the 2019 Ridgecrest, California, quakes shifted underground stresses, making the San Andreas fault—the state’s longest and most dangerous fault—three times more likely to rupture…. [https://www.sciencemag.org/news/2020/07/desert-quakes-may-have-boosted-chances-big-one-striking-california]
2020-05-18. A Plate Boundary Emerges Between India and Australia. By Katherine Kornei, Eos/AGU. Excerpt: Tectonic plates blanket the Earth like a patchwork quilt. Now, researchers think they’ve found a new plate boundary—a line of stitching in that tectonic quilt—in the northern Indian Ocean. This discovery, made using bathymetric and seismic data, supports the hypothesis that the India-Australia-Capricorn plate is breaking apart, the team suggests. …In 2012, two enormous earthquakes occurred near Indonesia. But these massive temblors—magnitudes 8.6 and 8.2—weren’t associated with the region’s notorious Andaman-Sumatra subduction zone. Instead, they struck within the India-Australia-Capricorn plate, which made them unusual because most earthquakes occur at plate boundaries. These earthquakes “reactivated the debate” about the India-Australia-Capricorn plate, said Aurélie Coudurier-Curveur, a geoscientist at the Institute of Earth Physics of Paris. Some scientists have proposed that this plate, which underlies most of the Indian Ocean, is breaking apart. That’s not a wholly unexpected phenomenon because this plate is being tugged in multiple directions, said Coudurier-Curveur…. [https://eos.org/articles/a-plate-boundary-emerges-between-india-and-australia] .
2020-05-18. Mount St. Helens 40 years later: what we’ve learned, and still don’t know. By Warren Cornwall, Science Magazine. Excerpt: Charlie Crisafulli first visited Mount St. Helens 2 months after the 18 May 1980 eruption that ripped the top off the volcano, obliterated 600 square kilometers of forests, killed 57 people, and coated much of the Pacific Northwest in ash. He was a 22-year-old with an undergraduate degree in ecology…. Since then, Crisafulli—now an ecologist at the U.S. Forest Service’s Pacific Northwest Research Station—has spent much of each summer taking the mountain’s pulse as life returns. He recently spoke with ScienceInsider about the 40th anniversary of the eruption that has defined his scientific career, and shaped people’s understanding of how ecosystems respond to such devastation. …Q: Are you still monitoring some of those same plots? A: There’s pieces of rebar that form the boundaries of plots I pounded in when I was 22 years old. I’m 62 now, and I’ve returned to those plots every year. And so for many of these things, there’s a tremendous amount of attachment to them. …Q: What are some of the key scientific insights from the work? A: The initial impression was that nothing could have survived this level of disturbance and that the regeneration of the area’s ecology is going to come from the edges and from distant source populations. Instead what we found is that, in some 90% of the landscape, the rule was survivorship, albeit at greatly reduced numbers and in isolated refugias. …What we’ve learned is that incredibly complex, early seral habitats [woodlands dominated by shrubs and grasses] developed that are food rich…. Even from space today, Mount St. Helens jumps out at you as this huge patch of something that’s different. What you’re looking down on is a landscape that supports a tremendous biomass of neotropical migrant birds, such as yellow warblers, orange-crowned warblers and willow flycatchers, and very diverse small mammal communities that are fundamentally different from adjacent old growth forests…. [https://www.sciencemag.org/news/2020/05/ecologist-has-been-studying-mount-st-helens-it-erupted-40-years-ago]
2020-05-08. Are We Seeing a New Ocean Starting to Form in Africa? By Erik Klemetti, Eos/AGU. Excerpt: …The entire Afar region in eastern Africa finds itself in the middle of changes that could split the continent, forming a new ocean basin. The magmatism at Erta Ale might be offering signs of this switch by mimicking the characteristics of a mid-ocean ridge. … What we will be able to see standing on top of Erta Ale will change dramatically in 5 million, 50 million, or 100 million years. The question is whether Erta Ale and the Afar region will become a new ocean, or whether ongoing tectonic collisions to Africa’s north and east will prevent this transition from occurring…. [https://eos.org/articles/are-we-seeing-a-new-ocean-starting-to-form-in-africa]
2020-01-06. Earthquake Strikes Puerto Rico, Toppling a Well-Known Natural Wonder. By Alejandra Rosa and Patricia Mazzei, The New York Times. [https://www.nytimes.com/2020/01/06/us/puerto-rico-earthquake.html] Excerpt: …The strong earthquake and persistent aftershocks that rattled Puerto Rico on Monday damaged vulnerable homes, destroyed a photogenic rock formation and terrified residents scarred by recent hurricanes about the prospect of another devastating disaster. The quake, which struck at 6:32 a.m. local time, according to the United States Geological Survey, was the strongest to be felt in the coastal towns west of the city of Ponce that have been trembling for more than a week. …Puerto Rico lies near the border of the North American and Caribbean tectonic plates. “We’re just as likely to have earthquakes as a place like California, Japan, New Zealand, Alaska,” Dr. Vanacore said….
2019-12-26. Seismic Sensors in Orbit. By Timothy I. Melbourne, Diego Melgar, Brendan W. Crowell, and Walter M. Szeliga, Eos/AGU. [https://eos.org/features/seismic-sensors-in-orbit] Excerpt: … Global Navigation Satellite Systems (GNSS). These systems comprise constellations of Earth-orbiting satellites whose signals are recorded by receivers on the ground and used to determine the receivers’ precise locations through time. GPS is the U.S. system, but several countries, or groups of countries, also operate independent GNSS constellations, including Russia’s GLONASS and the European Union’s Galileo system, among others. Prominently used for navigational purposes, GNSS ground receivers, which in recent years have proliferated by the thousands around the world, now offer useful tools for rapidly and accurately characterizing large earthquakes—supplementing traditional seismic detection networks—as well as many other natural hazards. …GNSS will never replace seismometers for immediate earthquake identifications because of its vastly lower sensitivity to small ground displacements. But for large earthquakes, GNSS will likely guide the issuance of rapid-fire revised warnings as a rupture continues to grow throughout and beyond the timing of initial, seismometer-based characterization [Murray et al., 2019]….
2019-08-16. Sinking Wastewater Triggers Deeper, Stronger Earthquakes. By Mary Caperton Morton, Eos/AGU. [https://eos.org/articles/sinking-wastewater-triggers-deeper-stronger-earthquakes] Excerpt: The effects of pumping wastewater from oil and gas extractions may last a decade or more after the injections stop. The oil and gas industry’s practice of pumping wastewater fluids underground for disposal has been implicated in the dramatic uptick in earthquakes in the central United States. Now a new study has found a correlation between the increasing depth of the earthquakes and the rate at which these fluids descend through Earth’s crust, a finding that could have implications for how such fluids are regulated. Over the past decade, earthquakes in the central United States greater than magnitude 3.0 have increased dramatically because of disposal of oil field wastewater into deep geologic formations. Injecting these fluids under pressure can destabilize faults and, in some places, trigger hundreds of induced earthquakes a year over magnitude 3.0, some as large as the magnitude 5.8 quake that struck Pawnee, Okla., in 2016. …the new study, published in Nature Communications [https://www.nature.com/articles/s41467-019-11029-8]….
2019-07-26. Sea of Galilee earthquakes triggered by excessive water pumping. By Michael Price, Science Magazine. [https://www.sciencemag.org/news/2019/07/sea-galilee-earthquakes-triggered-excessive-water-pumping] Excerpt: One evening in September 2013, windows rattled and ceiling fans swayed in northeastern Israel as a small earthquake rumbled beneath the Sea of Galilee—the water Jesus is said to have walked on—also known as Lake Kinneret. Four more tremors struck over the next 4 days. Then, in July 2018, a dozen small earthquakes shook the same spot beneath the lake on a fault—the slip surface along which an earthquake ruptures. …A new study suggests human activity is to blame. Pumping too much water from the region too quickly may have “unclamped the fault,” the authors argue. And, they add, Californians and others living above major faults better pay attention, lest a similar appetite for water trigger a far larger, more dangerous quake….
2019-06-03. Déjà Vu: Understanding Subduction Zones’ Cycle of Seismicity. By Terri Cook, Eos/AGU. [https://eos.org/research-spotlights/deja-vu-understanding-subduction-zones-cycle-of-seismicity] Excerpt: A unique geodetic data set from Japan’s Nankai subduction zone offers an unparalleled opportunity to study surface deformation spanning almost an entire seismic cycle….
2019-01-25. Earth’s Devastating Power, Seen by Satellite. By Kimberly M. S. Cartier, Eos/AGU. [https://eos.org/features/earths-devastating-power-seen-by-satellite] Excerpt: Hurricanes, volcanoes, droughts, floods, fires, tsunamis: Satellites capture some of Earth’s most destructive forces. Earth-orbiting satellites can inspire awe of the beauty of our planet and provide breathtaking vantage points from which scientists can study its complicated dynamics. Satellites are cataloging Earth’s changing ice coverage, measuring water content inside leaves, monitoring air pollution, and tracking illegal fishing operations to protect marine ecosystems. These satellites are also a key resource for people who study natural disasters and those who respond to them. Governments and disaster relief agencies use satellite images and data to pinpoint areas that are at risk, track the progress of ongoing disasters, and monitor the impact on affected regions. Scientists use these data to study rare phenomena caused by intense conditions, refine models to predict future events, and inform policies that seek to minimize damage and save lives. These six images of recent natural disasters, all taken by Earth-orbiting satellites, demonstrate our planet’s raw power and show how satellite images and data can detect and monitor catastrophes around the world…. [Images are a “must see”]
2018-11-01. California’s new earthquake warnings deliver critical seconds of notice. By Paul Voosen, Science Magazine. [https://www.sciencemag.org/news/2018/11/california-s-new-earthquake-warnings-deliver-critical-seconds-notice] Excerpt: For years, ShakeAlert was an academic side project of California seismologists, especially the gravelly voiced Heaton, now at the California Institute of Technology (Caltech) in Pasadena, and Richard Allen, his soft-spoken counterpart at the University of California (UC), Berkeley. They were inspired by warning systems in Mexico, Japan, Taiwan, and Chile, among others, which emphasize detecting earthquakes at the source and warning distant cities before the seismic waves arrive. Many people thought such a system would be useless in fault-riddled California, where earthquakes seem to erupt underfoot anywhere. But Heaton and Allen persevered, deploying a pilot system in 2012. …Los Angeles Mayor Eric Garcetti pledged: “By the end of 2018, we will deploy an earthquake early warning system to every corner of this city—in schools, at businesses, even on your smartphone.” This year’s version doesn’t quite measure up to that promise. Only half of the system’s 1675 seismic stations have been installed. The technology to rapidly push alerts to mobile phones is not mature. And the public has yet to be trained in how to respond to such alerts, which are sure to include false alarms. …USGS has set one important parameter: Instead of waiting until a risk is severe, ShakeAlert will skew toward more alerts, sounding an alarm once a location is at risk of “light shaking.” That will increase the warning time—but it also will mean that, if the rupture grows, the prediction could change to severe shaking only seconds before hitting. And the public might grow complacent about those alarms and fail to respond to the rare mild threat that, in a moment, turns severe….
2018-09-21. This ice-covered Icelandic volcano may emit more carbon dioxide than all of the country’s other volcanoes combined. By Sid Perkins, Science Magazine. [https://www.sciencemag.org/news/2018/09/ice-covered-icelandic-volcano-may-emit-more-carbon-dioxide-all-country-s-other] Excerpt: Despite being mostly smothered by a glacier averaging 200 meters thick, one of Iceland’s largest and most active volcanoes still manages to belch surprisingly large quantities of carbon dioxide (CO2) into the atmosphere, new research reveals. To help lift the veil on Katla … which lies near the southernmost tip of Iceland, researchers flew a sensor-laden aircraft around the peak at low altitude three times in 2016 and 2017. At some points near the volcano, CO2 levels were about 8% higher than normal. …Katla is emitting somewhere between 12,000 and 24,000 metric tons of carbon dioxide each day … several times higher than previous estimates of emissions from all of Iceland’s volcanoes combined—which may be vastly underestimated because only two of that nation’s subglacial volcanoes have had their emissions measured in detail. Scientists estimate that volcanoes worldwide emit, on average, about 1.5 metric tons of CO2 per day (only about 2% of the amount that human activity causes). Yet that estimate may be far too low because it’s based on measurements from only 33 of the world’s most volcanically active peaks (only three of which are ice-covered), among the 1500 or so that have erupted in the past 10,000 years….
2018-05-03. Vanuatu plans to permanently evacuate entire volcanic island. By Associated Press. Excerpt: The Pacific nation of Vanuatu is preparing to permanently evacuate the entire population of one of its islands as thick ash spewing from a volcano kills crops, dirties water supplies and fouls the air. The 10,000 or so people who remain on Ambae island have mixed feelings about the plans. Some who are badly affected by the ash are eager to leave while others are resisting losing their land and culture…. https://www.cnbc.com/2018/05/03/vanuatu-plans-to-permanently-evacuate-entire-volcanic-island.html
2018-03-30. Are We Prepared for the Next Mega Eruption? By Fabio Florindo, AGU-Eos. Excerpt: In April 1815, Mount Tambora, on the Indonesian island of Sambawa, experienced a colossal eruption, with a rating of 7 on the Volcanic Explosivity Index (VEI). Tens of thousands of people died, about 100 cubic kilometers of rock blasted into the air, and the resulting sulfate aerosol in the upper atmosphere led to drastic weather changes in North America and Europe, causing food shortages. The following year, 1816, is known as the “Year without a Summer” due to the major climate abnormalities, and proved to be inspirational for art and literature (for example, Lord Byron, Mary Shelley, J.M.W. Turner). A previous VEI 7 eruption in the region, of the Indonesian volcano Samalas at Mount Rinjani in 1257 CE was implicated in the onset of a centuries-long cold period between the 14th and the 19th century called the Little Ice Age. Fortunately, the recurrence frequency of VEI 7 eruptions somewhere in the world is between one and two per thousand years, but this should not cause complacence in preparing for future events. Volcanologist Chris Newhall, with co-authors Stephen Self and Alan Robock, have recently published a paper in Geosphere exploring the potential consequences of the next VEI 7 eruption…. https://eos.org/editors-vox/are-we-prepared-for-the-next-mega-eruption
2018-03-12. After a Volcano’s Ancient Supereruption, Humanity May Have Thrived. By Shannon Hall, The New York Times. Excerpt: About 74,000 years ago, a supervolcano at the site of present-day Lake Toba on the Indonesian island of Sumatra rocked our world. But while it was the largest volcanic eruption of the last two million years, a new study published Monday in Nature suggests that humans not only survived the event — they thrived. The study counters previous hypotheses, which suggested that the behemoth was so disastrous it caused the human species to teeter on the brink of extinction. … Climate models suggest that temperatures may have plummeted by as much as 30 degrees Fahrenheit. And in such a cold world, plants may have ceased growing, glaciers may have advanced, sea-levels may have dropped and rainfall may have slowed. Then in 1998, Stanley Ambrose, an anthropologist, linked the proposed disaster to genetic evidence that suggested a population bottleneck had occurred around the same time. He was certain that the Toba supereruption had caused the human population to decline to some 10,000 people — a close call for our ancestors. …The latest study, however, suggests that those theories are incorrect, Dr. Petraglia said. “We’re not seeing all the drama.”…. https://www.nytimes.com/2018/03/12/science/toba-supervolcano-supereruption.html
2018-02-09. At Site of Japanese Volcano’s Supereruption, an Immense Lava Dome Lurks. By Nicholas S. Fleur, The New York Times. Excerpt: Some 7,300 years ago, a supereruption devastated the southern islands of what is now Japan, burying most of the archipelago in thick ash. Known as the Akahoya eruption, the blast was so powerful it caused the volcano’s magma chamber to collapse, leaving a 12-mile wide scar called Kikai Caldera, which is mostly underwater. Now in a study published Friday, scientists have discovered that a dome of lava lurks beneath the caldera. By studying its magma plumbing, volcanologists could gain insight into the entire caldera system, which could help them better predict when another eruption in the Japanese archipelago might occur. “The most serious problem that we are worrying about is not an eruption of this lava dome, but the occurrence of the next supereruption,” said Yoshiyuki Tatsumi a volcanologist at Kobe University in Japan and lead author of the study that appeared in the journal Scientific Reports…. https://www.nytimes.com/2018/02/09/science/japan-volcano-supereruption.html
2017-12-27. Scientists Discover Stromboli-Like Eruption on Volcanic Moon. By JoAnna Wendel, Eos/AGU. Excerpt: Jupiter’s moon Io is known for its lava fountains and roiling lava lakes, but scientists had never seen such an intense eruption in their data until now. …But wait, you ask, didn’t Galileo plunge into Jupiter’s atmosphere at the end of its mission, way back in 2003? Well, yes. But the orbiter, at that point, had collected so much data about the Jovian system and its Galilean moons (Ganymede, Io, Callisto, and Europa) that scientists still haven’t waded through it all, even 14 years later. …Io’s surface is constantly gushing lava—every million years or so, the entire moon’s surface completely regenerates. From towering lava fountains that can reach 400 kilometers high to violently bubbling lava lakes that burst through freshly cooled crust, these oozing lava fields can stretch many thousands of square kilometers. On this 3,600-kilometer-wide moon, eruptions take place “on a scale that simply isn’t seen on Earth today but was once common in Earth’s past,” Davies said. The scale, frequency, and intensity of Io’s eruptions make it a perfect analogue of early Earth, he continued, back when our blue planet was just a barren hellscape of lava. Video of the eruption: https://eos.org/wp-content/uploads/2017/12/IoGIF.gif?x35494 …. https://eos.org/articles/scientists-discover-stromboli-like-eruption-on-volcanic-moon
2017-10-17. How to Trigger a Massive Earthquake. By Lucas Joel, Eos/AGU. Excerpt: Humans may be to blame for California’s second-largest 20th century earthquake, and a team of seismologists has now proposed how that could have happened. A Los Angeles Times article published on 11 June 1952 tells of a successful new oil well at Wheeler Ridge in Kern County in California. The well operated for 98 days, but then, on 21 July at 4:52 a.m. local time, a 7.5-magnitude earthquake let loose beneath the well along the White Wolf fault. It was the second-largest earthquake in California in the 20th century, and it killed 12 people. A team of seismologists, reporting new research, thinks the oil drilling triggered the event. The work is the first to give a detailed explanation for how industrial activity could cause such a big earthquake, the researchers said. Taking oil out of the ground likely destabilized the White Wolf fault, triggering the Kern County quake, explained Susan Hough, a seismologist at the U.S. Geological Survey in Pasadena, Calif., and lead author of a study published this month in the Journal of Seismology…. https://eos.org/articles/how-to-trigger-a-massive-earthquake
2017-10-10. A Surprise From the Supervolcano Under Yellowstone. By Shannon Hall, The New York Times. Excerpt: Beneath Yellowstone National Park lies a supervolcano, a behemoth far more powerful than your average volcano. It has the ability to expel more than 1,000 cubic kilometers of rock and ash at once — 2,500 times more material than erupted from Mount St. Helens in 1980, which killed 57 people. That could blanket most of the United States in a thick layer of ash and even plunge the Earth into a volcanic winter. Yellowstone’s last supereruption occurred 631,000 years ago. And it’s not the planet’s only buried supervolcano. Scientists suspect that a supereruption scars the planet every 100,000 years, causing many to ask when we can next expect such an explosive planet-changing event. To answer that question, scientists are seeking lessons from Yellowstone’s past. And the results have been surprising. They show that the forces that drive these rare and violent events can move much more rapidly than volcanologists previously anticipated. The early evidence, presented at a recent volcanology conference, shows that Yellowstone’s most recent supereruption was sparked when new magma moved into the system only decades before the eruption. Previous estimates assumed that the geological process that led to the event took millenniums to occur…. https://www.nytimes.com/2017/10/10/science/yellowstone-volcano-eruption.html
2017-09-22. Scientists Closing in on the Dawn of Plate Tectonics. By Shannon Hall, Scientific American. Excerpt: Geologists think early Earth may have looked much like Iceland—where jet-black lava fields extend as far as the eye can see, inky mountainsides rise steeply above the clouds and stark black-sand beaches outline the land. But over time the world gradually became less bleak. Today Earth also harbors light-colored rocks, like the granite that composes Half Dome in Yosemite National Park. But scientists remain uncertain as to when the world started to transition from the one that looked like Iceland to that which we know today. A new study published Thursday in Science suggests the shift transpired more than 3.5 billion years ago. Not only does the finding tell scientists the color of the world’s early beaches, it might help them understand when tectonic plates—the interlocking slabs of crust that fit together like puzzle pieces far beneath our feet—started to wake up and shuffle around. That is because the lighter-colored rocks, known as felsic rocks, are actually dark, or mafic, rocks “reincarnated.” In short, felsic rocks form when mafic ones are pushed deep inside Earth—possibly when one tectonic plate slips under another in a process called subduction. Given that light-colored felsic rocks were abundant billions of years ago, plate tectonics had likely already kicked into action…. https://www.scientificamerican.com/article/scientists-closing-in-on-the-dawn-of-plate-tectonics1/
2017-06-29. Homemade Lava Flows Fuse Science with Art on Video. By Lauren Lipuma and Derek Sollosi, Earth & Space Science News (EoS, AGU). Excerpt: …residents of upstate New York can see real-life lava flowing much as it does in Hawaii, Iceland, and Italy. The glowing molten rock spills from an outdoor furnace in the Syracuse, N.Y., where an artist and scientist at a local university have teamed up to recreate natural lava flows. Their scorching outpourings provide a better understanding of the mechanics of volcanic eruptions and solidify into replicas of volcanic discharges that the duo would like to display in museums or other unlikely settings for puddles of lava. …By documenting each experiment’s variables, such as lava temperature, gas content, and speed of flow, the Syracuse lava experimenters are illuminating the conditions under which volcanic features like lava pillows form…. https://eos.org/articles/homemade-lava-flows-fuse-science-with-art-on-video
2017-06-26. New Volcanic Island Unveils Explosive Past. By Shane J. Cronin, Marco Brenna, Ian E. M. Smith, Simon Barker, Manuela Tost, Murray Ford, Sisi Tonga’onevai, Taaniela Kula, and Rennie Vaiomounga, Earth & Space Science News (EoS, AGU) Excerpt: In late December 2014, an undersea volcano erupted between two small islands in the Tonga volcanic arc northeast of New Zealand, sending steam and dense ash plumes high into the air. By the time the eruption ended about 5 weeks later, a new island had formed, eventually bridging the gap between the original islands. Winds and ocean waves then began rapidly reshaping the newly emerged volcanic cone. Ten months after the eruption, we visited the new island, which we unofficially nicknamed Hunga Island. There, we attempted to characterize the volcanology of the eruption, begin tracking the rate of erosion on the new island, and assemble a history of volcanism in this region of the southwest Pacific. Our findings reveal a shallow submarine volcanic caldera adjacent to the new volcanic island, and they highlight how incomplete the volcanic record can be at remote oceanic volcanoes…. https://eos.org/project-updates/new-volcanic-island-unveils-explosive-past
2017-06-22. “Fingerprinting” Volcanic Tremors May Help Forecast Eruptions. By Lucas Joel, for Earth & Space Science News, EoS, AGU. Excerpt: Volcanic tremors can mean that an eruption is imminent—or maybe not. When it comes to linking tremors with impending eruptions, researchers are still very much in the dark. In a new study, however, one team of volcanologists revealed the existence of distinct tremor patterns, or tremor “fingerprints,” as they call them, shared among different kinds of volcanoes. Observations of such fingerprints may provide a small advance toward improved eruption forecasting. If, in the future, a volcano produces a fingerprint already found to have preceded or accompanied other eruptions, volcanologists might be better able to say whether an eruption will occur. The team behind the study discovered the fingerprints by looking at seismic signals produced by four volcanoes: Okmok, Redoubt, and Pavlof in Alaska and Kīlauea in Hawaii. Kīlauea and Okmok are shield volcanoes, which are generally broad, gently sloping volcanoes constructed by relatively fluid lava. Pavlof and Redoubt are stratovolcanoes, which are more conical volcanoes made from lava more viscous than that which creates shield volcanoes. Generally, higher viscosity of the molten rock yields more violent eruptions…. https://eos.org/wp-content/uploads/2017/05/June-17_magazine.pdf
2017-04-13. What Led to the Largest Volcanic Eruption in Human History? By Sarah Witman, Earth & Space Science News (AGU). Excerpt: A mineral-dating project at the Toba caldera in Indonesia sheds light on the science of supereruptions. In the northern part of the Indonesian island of Sumatra lies the Toba caldera, a massive crater formed by what scientists think is the largest volcanic eruption ever experienced by humanity. The eruption, called the Youngest Toba Tuff supereruption, took place about 74,000 years ago. By dating zircon, a diamond-like gemstone, and other minerals in the area such as quartz, Reid and Vazquez https://doi.org/10.1002/2016GC006641 have pieced together clues about the activity of magma below the surface prior to the supereruption. …Because zircon does not gain or lose uranium or lead even at magmatic temperatures, zircon typically contains high uranium and low lead levels, and scientists may use the ratio of these two elements in the zircon to determine the age of the sample. …The team’s findings are significant for modern-day humans, given that aerosols and ash that erupted from Youngest Toba Tuff are thought to have entered the atmosphere, causing global cooling and the near extinction of the human race. A supereruption of equal or greater magnitude today could therefore have similarly drastic consequences. By better understanding the conditions that led up to the Youngest Toba Tuff supereruption, scientists can help paint a clearer picture of the future. (…https://doi.org/10.1002/2016GC006641, 2017) https://eos.org/research-spotlights/what-led-to-the-largest-volcanic-eruption-in-human-history
2016-11-18. Fracking can prime faults for subsequent quakes. By Ian Randall, Science. Excerpt: Hydraulic fracturing in western Canada can prime faults for earthquakes that strike months after fracking ceases, reports a new study published this week in Science. Although it has long been known that the injection of wastewater into disposal wells can trigger earthquakes by increasing pore pressure and destabilizing fault lines, rarely has fracking itself been identified as the source of tremors. …Looking at seismic records near Fox Creek, in northwest Alberta, where there are six drilling sites, researchers found an intermittent set of induced earthquakes between December 2014 and March 2015, clustered around fracking operations. The majority of seismicity occurred during fracking as the elastic response of the rock caused mounting stress. However the largest quake, which had a magnitude of 3.9, struck on 23 January 2015—2 weeks after fracking had been completed. …In the future, they say, drillers should take account of such risks, especially when they fail to recover fracking fluids…. http://www.sciencemag.org/news/2016/11/fracking-can-prime-faults-subsequent-quakes
2016-11-09. An Ancient Tsunami That Ended a Civilization Gets Another Look. By Henry Fountain, The New York Times. Excerpt: In the 17th century B.C., Santorini was a small volcanic island in the Aegean Sea, home to Akrotiri, a Late Bronze Age outpost of Minoan civilization, which preceded ancient Greece. Then the volcano erupted, burying Akrotiri in ash and obliterating much of Santorini, turning it into a few smaller islands. The eruption was one of the world’s most powerful in the past 10,000 years, spewing some 20 cubic miles of rock into the skies and spawning a tsunami that struck the nearby island of Crete, which was the center of Minoan culture. Many archaeologists believe the tsunami was disruptive enough that the Minoans became easier prey for the outside invaders who conquered them a century and a half later and brought an end to one of the first European civilizations. But what caused the tsunami? Research published Tuesday, including seafloor surveys, suggests that it was likely caused by huge amounts of hot ash and lava spewing from the volcano — what volcanologists call pyroclastic flows — and pouring down its slopes into the water at high speed. The study contradicts earlier explanations that the tsunami must have been the result of a caldera collapse, which occurs when the crust above a volcano’s magma chamber slips swiftly downward as the chamber empties during an eruption…. http://www.nytimes.com/2016/11/10/science/santorini-akrotiri-tsunami.html
2016-10-20. This volcano stopped an earthquake in its tracks, scientists say. By Ian Randall, Science. Excerpt: Before they break a volcano’s heart, earthquakes must stop in the name of lava. That’s the conclusion of a new study, which reports that Japan’s 2016 Kumamoto earthquake may have been stopped in its tracks by the magma chamber underneath the active volcano Mount Aso. The study offers insight into the interplay between earthquakes and volcanoes—and it may also help explain Mount Aso’s explosive eruption this month…. http://www.sciencemag.org/news/2016/10/volcano-stopped-earthquake-its-tracks-scientists-say
2016-07-18. Spring tides trigger tremors deep on California’s San Andreas fault. By Eric Hand, Science. Excerpt: …Below the town of Parkfield, California, hundreds of thousands of slow microearthquakes called tremors go off routinely where Earth’s brittle crust gets weaker and softer. Now, scientists have shown that these tremors are triggered by the rhythmic pulsing of the tides: not just the twice-daily tides that occur as the moon revolves around Earth, but also the twice-monthly spring tides that occur when the sun and moon align and pull strongly on the planet. The finding gives scientists a new window into a deeper part of the San Andreas fault, and new insight into how stress builds up on small patches of the fault until they snap. …as seismometers got more sensitive and were laid down in more places, scientists started to identify tremors in the lower crust. In these deeper regions, faults are weaker, and that means that tides can play a more important role. In 2012, scientists spotted deep tremors on the San Andreas fault below Parkfield that were tidally triggered, at the twice-a-day tidal peaks associated with the lunar day. In the new study, Van der Elst and his team found that bursts of tremors were also triggered during waxing of the twice-monthly spring tides, when the moon is aligned with the sun. Using a catalog of 4 million tremors that occurred between 2008 and 2015, they pinpointed the location and timing of the tremors in relation to the tides, they report today in the Proceedings of the National Academy of Sciences. …The tremors can’t predict the next “big one,” but in the long term, they could help scientists understand how big ones are set off…. http://www.sciencemag.org/news/2016/07/spring-tides-trigger-tremors-deep-california-s-san-andreas-fault
2016-06-02. A New View of the Plate Dynamics Behind Earthquakes in Ecuador. By Sarah Stanley, EoS-Earth & Space Science News, AGU. Excerpt: On 16 April, a magnitude 7.8 earthquake struck coastal northern Ecuador, killing hundreds of people and injuring thousands more. The quake hit in the midst of ongoing efforts to update a map of seismic hazards throughout the earthquake-prone country. In a recent paper, Yepes et al. present a new interpretation of the mantle dynamics behind Ecuadorean tremors, and they identify 19 seismic zones that contribute to earthquake risk. Ecuador is no stranger to deadly quakes. It lies above a subduction zone where the Nazca Plate plunges beneath the South American Plate, giving rise to a long history of seismic activity. Complicating this subduction is how the Nazca plate itself seems split into two sections by the Grijalva rifted margin, which cuts southwest to northeast beneath central Ecuador. …A simplified picture models the subduction interface as dipping fault planes. However, Ecuador’s individual crustal faults and fault systems are complex. Despite their importance to hazard assessments, these systems are still poorly studied so Yepes’s team focused on defining seismic zones…. https://eos.org/research-spotlights/a-new-view-of-the-plate-dynamics-behind-earthquakes-in-ecuador
2016-05-17. Rumbling under the Volcanoes. By UC Berkeley Seismological Laboratory. Excerpt: First it was Mount St. Helens in Washington, now it is Mount Hood in Oregon. Recently, hundreds of small earthquakes have been detected under these two slumbering volcanoes. Is something ominous brewing in the Cascade Range this spring? Are we in for another catastrophic eruption similar to the one which obliterated a large part of Mount St. Helens exactly 36 years ago tomorrow? While no serious Earth scientist will ever rule out a surprise eruption completely, all experts dealing with volcanism in the Cascade Range do not see the recent earthquake swarms as a sign of imminent danger on either of the two fire mountains. In fact, monitoring seismicity is currently the most powerful tool in understanding the behavior of magma inside a volcanic edifice. …Over the years, seismologists have detected many kinds of such magmatically driven earthquakes, the most common being the so-called “volcano tectonic” or VT-events. A detailed observation of such quakes can even be used to predict imminent eruptions in a reliable fashion. …Luckily, none of the quakes in the current earthquakes swarms under the two Cascadian volcanoes were of that critical type…. http://seismo.berkeley.edu/blog/seismoblog.php/2016/05/17/rumbling-under-the-volcanoes
2016-05-16. Understanding Volcanic Eruptions Where Plates Meet. By Raffaele Azzaro and Rosanna De Rosa, EoS-Earth & Space Science News (AGU). Excerpt: A new project elucidates the relationships between tectonics and volcanic systems and how they influence hazards on Italy’s Mount Etna and Vulcano and Lipari islands…. https://eos.org/project-updates/understanding-volcanic-eruptions-where-plates-meet
2016-04-26. Crowdsourced Seismology. By Elizabeth Deatrick, EoS Earth and Space Science News (AGU). Excerpt: The seismologists of the world want to turn you into an earthquake detector. …At the Seismological Society of America (SSA) meeting last week, in a session on “Citizen Seismology,” researchers from around the globe presented their crowdsourced earthquake detection networks. From cell phone apps to sensors in basements, these projects recruit ordinary people to gather and report data on nearby earthquakes. They generate dense networks of sensors while also teaching their citizen volunteers about earthquakes. Made possible by the advent of the Internet and smartphones, this distributed way of gathering data can sometimes make up for shortfalls of traditional precision seismograph networks, seismologists said…. https://eos.org/articles/crowdsourced-seismology
2016-01-15. Quake or Bomb? Seismic Waves Speak Truth, Even If Nations Don’t. By Cody Sullivan, Earth & Space News (EoS; AGU). Excerpt: Last week, North Korea tested what it claimed to be a hydrogen bomb, or as the North Korean government declared in its official statement, an “H-Bomb of justice.” However, it’s not likely that North Korea has actually developed a hydrogen bomb and successfully tested it on 6 January local time (the evening of 5 January on the U.S. East Coast), as announced. The U.S. Geological Survey recorded the subsequent seismic event as having a 5.1 magnitude, which is much lower than would be expected from such a powerful weapon. But even if North Korea or anyone else conducting a clandestine nuclear test makes no announcement, seismologists can still figure out if an underground bomb test or an earthquake took place by analyzing how energy propagates from the seismic event in question…. https://eos.org/articles/quake-bomb-seismic-waves-speak-truth-even-nations-dont
2016-01-12. The 40,000-Mile Volcano. By William J. Broad, The New York Times. Excerpt: …Recently, Dr. Tolstoy of Columbia University drew on such acoustic data from nine seabed eruptions over nearly two decades to paint a group portrait full of surprises. It turned out that all of those eruptions, from the Pacific, Atlantic and Arctic Oceans, took place from January to June. …The cause, she proposed, is Earth’s slightly elliptical orbit around the sun. That changes the strength of the sun’s gravitational pull on Earth during the year and, as a result, the magnitude of the tides that squeeze the planet. She said the eruptions coincided with the annual letup of the squeeze. More boldly, Dr. Tolstoy suggested that such mechanisms might help explain how the planet’s regular ice ages end so abruptly — long a mystery. Ocean levels fall sharply in such bitterly cold periods as water is tied up in massive continental ice sheets. In a paper, she proposed that the reduced pressure on the ridges might let them erupt far more frequently. As a result, more carbon dioxide would spew into the ocean and, eventually, into the atmosphere, trapping more heat and warming the planet…. http://www.nytimes.com/2016/01/12/science/midocean-ridges-volcano-underwater.html
2016-01-04. Pinpointing the Trigger Behind Yellowstone’s Last Supereruption. By Aylin Woodward, EoS – Earth & Space Science News, AGU. Excerpt: Yellowstone National Park is renowned for more than just its hot springs and Old Faithful. The area is famous in the volcanology community for being the site of three explosive supereruptions, the last of which was 631,000 years ago. Map of known ashfall boundaries for major eruptions from Yellowstone, with Long Valley and Mount St. Helens for comparison. During that eruption, approximately 1000 cubic kilometers of rock, dust, and volcanic ash blasted into the sky. Debris rained across the continental United States, spanning a rough triangle that stretches from today’s Canadian border down to California and over to Louisiana. In places, ash reached more than a meter thick. “If something like this happened today, it would be catastrophic,” said Hannah Shamloo, a geologist at Arizona State University’s School of Earth and Space Exploration in Tempe. “We want to understand what triggers these eruptions, so we can set up warning systems. That’s the big-picture goal.” Now, Shamloo and her coauthor think they’ve found a clue. By examining trace elements in crystals that they found in the volcanic leftovers of Yellowstone’s last supereruption, they might be able to pinpoint what triggered it…. https://eos.org/articles/pinpointing-the-trigger-behind-yellowstones-last-supereruption
2015-11-12. Better Forecasting for the Next Volcanic Eruption. By Valerio Acocella and Giovanni Chiodini. EoS Earth & Space Science News, AGU. Excerpt: The Eruptive Precursors project in Campi Flegrei, Italy, seeks to understand conditions leading to caldera eruptions…. https://eos.org/project-updates/better-forecasting-for-the-next-volcanic-eruption
2015-08-24. How a Volcanic Eruption in 1815 Darkened the World but Colored the Arts. By William J. Broad, The New York Times. Excerpt: In April 1815, the most powerful volcanic blast in recorded history shook the planet in a catastrophe so vast that 200 years later, investigators are still struggling to grasp its repercussions. It played a role, they now understand, in icy weather, agricultural collapse and global pandemics…. …Around the lush isles of the Dutch East Indies — modern-day Indonesia — the eruption of Mount Tambora killed tens of thousands of people. …More surprising, investigators have found that the giant cloud of minuscule particles spread around the globe, blocked sunlight and produced three years of planetary cooling. In June 1816, a blizzard pummeled upstate New York. …A recent history of the disaster, “Tambora: The Eruption that Changed the World,” by Gillen D’Arcy Wood, shows planetary effects so extreme that many nations and communities sustained waves of famine, disease, civil unrest and economic decline. Crops failed globally…. Thomas Jefferson…Jefferson expressed concern about the possible ruin of his Monticello farm “if the seasons should, against the course of nature hitherto observed, continue constantly hostile to our agriculture.” The countless victims and occasional beneficiaries of Tambora’s fury were oblivious to the volcanic roots of their circumstances, Dr. Wood noted, making the challenge of writing about it formidable and “occasionally mind-bending.”… http://www.nytimes.com/2015/08/25/science/mount-tambora-volcano-eruption-1815.html
2015-05-01. Nepal disaster presages a coming megaquake. By Eric Hand and Priyanka Pulla, Science. Excerpt: …As rescuers searched for survivors of a devastating earthquake in Nepal on 25 April, geophysicists made a disturbing discovery. An initial assessment suggests that the underground rupture responsible for the magnitude-7.8 quake extended deep below the Himalayas, into a region that many scientists had deemed impervious to tearing. The unexpected extent of the rupture suggests that, as awful as the present disaster is, future earthquakes in the Himalayas could end up being mightier—and more calamitous—than modelers assumed. The discovery “is going to radically change how we predict and interpret future and historic earthquakes,” says Roger Bilham, a geologist at the University of Colorado, Boulder. …The ultimate driver of Himalayan earthquakes is the slow-motion collision of the Indian subcontinent with mainland Asia, which is also pushing the mountains skyward. Some 15 kilometers below the surface, a nearly horizontal thrust fault marks the plane where the Indian plate is plunging beneath southern Tibet at a rate of about 18 millimeters per year. Microearthquakes—most of them too small to feel at the surface—cluster along a line that trends east to west across this plane. Most of the region’s substantial earthquakes have occurred south of the line, where the plates are locked together and strain builds up. North of this “lock line,” however, the Indian plate dives downward and the character of the rock slab changes. Under higher temperatures and rising pressures, the brittle rocks become more plastic, and they creep past the Tibetan crust without rupturing. Or so researchers had thought. The 25 April earthquake followed an ominous new rupture path. …the temblor ruptured crust well north of the lock line, suggesting the potential for future quakes with a far larger rupture area than seismologists had thought possible. …The Nepal disaster “could have been much worse had engineers not sprung into action to retrofit critical facilities in Kathmandu,” says Bilham, who has long sounded an alarm over the Himalayan earthquake hazard. But with an even greater threat looming, Nepal and its neighbors will have to take a hard look at their earthquake preparedness… http://www.sciencemag.org/content/348/6234/484.summary
2015-04-23. Two huge magma chambers spied beneath Yellowstone National Park. By Eric Hand, Science (AAAS). Excerpt: Underneath the bubbling geysers and hot springs of Yellowstone National Park in Wyoming sits a volcanic hot spot that has driven some of the largest eruptions on Earth. Geoscientists have now completely imaged the subterranean plumbing system and have found not just one, but two magma chambers underneath the giant volcano. “The main new thing is we unveil a deeper and bigger magma reservoir in the lower crust,” says study author Hsin-Hua Huang, a seismologist at the University of Utah in Salt Lake City. Scientists had already known about a plume, which brings molten rock up from deep in the mantle to a region about 60 kilometers below the surface. And they had also imaged a shallow magma chamber about 10 kilometers below the surface, containing about 10,000 cubic kilometers of molten material. But now they have found a deeper one, 4.5 times larger, that sits between 20 and 50 kilometers below the surface. …The last major eruption was 640,000 years ago, and today the threat of earthquakes is far more likely. But the deeper chamber does mean that the shallow chamber can be replenished again and again. “Knowing that you have this additional reservoir tells you you could have a much bigger volume erupt over a relatively short time scale,” says co-author Victor Tsai, a geophysicist at the California Institute of Technology in Pasadena. …Huang says that with rough dimensions now in hand for all the major magma bodies, modelers can try to understand how magma moved around in past eruptions—and why the chambers sit where they are…. http://news.sciencemag.org/earth/2015/04/two-huge-magma-chambers-spied-beneath-yellowstone-national-park
2015-04-23. Oil and gas operations could trigger large earthquakes. By Eric Hand, Science (AAAS). Excerpt: The U.S. Geological Survey (USGS) has taken its first stab at quantifying the hazard from earthquakes associated with oil and gas development. The assessment, released in a preliminary report today, identifies 17 areas in eight states with elevated seismic hazard. And geologists now say that such induced earthquakes could potentially be large, up to magnitude 7, which is big enough to cause buildings to collapse and widespread damage. The new bull’s-eyes on the map, regions such as central Oklahoma, have short-term hazards that are comparable to the those in traditional earthquake states, like California, says Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project in Golden, Colorado. “These earthquakes are occurring at a higher rate than ever before and pose a much greater threat to people living nearby,” he says. …Geoscientists have known for decades that the injection of fluid can increase pressures within the pores of deep rock formations, pushing faults that are already critically stressed by forces in Earth’s crust past the snapping point. But the phenomenon has been brought to the fore by an extraordinary rise in small earthquakes across parts of the central United States. That surge has coincided in time and place with the boom in unconventional oil and gas extraction such as hydraulic fracturing, or “fracking,” in which high-pressure fluid is injected into the ground to break up the underlying rock and release trapped gas or oil. In most cases, the earthquakes are not due to fracking itself, which is usually completed in hours or days. Rather, the culprit is typically wastewater disposal, where high volumes of water extracted in oil and gas operations is reinjected into deep basement rocks, where the bigger and more dangerous faults lie…. http://news.sciencemag.org/earth/2015/04/oil-and-gas-operations-could-trigger-large-earthquakes
See also http://www.nytimes.com/2015/04/24/us/us-maps-areas-of-increased-earthquakes-from-human-activity.html
2015-03-23. No Need to Run in Hawaii: The Lava Is Coming, but Very Slowly. By Diane Cardwell, The New York Times. Excerpt: PAHOA, Hawaii — If a disaster movie played out in slow motion, it might look a bit like the Puna District on the Big Island of Hawaii. As a mass of smoldering black lava has inched since June toward the town of Pahoa, the commercial center of this isolated stretch of Puna, there has been no need for residents to run screaming from a flaming river rumbling down the mountain. …“We’ve kind of been living day by day,” said Jeff Hunt, 55, a surfboard shaper with a shop along the main drag. “You just really don’t know how to act.” The Kilauea volcano is 35 miles away, and its magma has emerged routinely since 1983. Most of the time, when the lava exits the earth with enough force to creep far downhill, it heads south toward the ocean, following a course that is largely no longer inhabited. Starting last June 27, however, new fissures pushed the molten rock northeast, straight for this town of about 950. …“The good news is that you have plenty of time to evacuate, so you’re not going to die,” [Mark Kimura, a researcher affiliated with the University of Hawaii at Hilo] said. The bad news? No one can predict when or if the lava will hit the town, he said. “The worst is, even geologists don’t know the answer.”… http://www.nytimes.com/2015/03/24/us/as-volcano-erupts-around-them-hawaiians-pledge-to-gamely-go-with-the-flow.html.
2013-03-20. Scientists Discover Layer of Liquified Molten Rock in Earth’s Mantle | NSF Press Release 13-045. Relevant to GSS Energy Flow chapter 2. Excerpt: Scientists have discovered a layer of liquified molten rock in Earth’s mantle that may be responsible for the sliding motions of the planet’s massive tectonic plates. The finding may carry far-reaching implications, from understanding basic geologic functions of the planet to new insights into volcanism and earthquakes. …The scientists discovered the magma layer at the Middle America trench off Nicaragua’s shores. Using advanced seafloor electromagnetic imaging technology pioneered at SIO [Scripps Institution of Oceanography], the scientists imaged a 25-kilometer- (15.5-mile-) thick layer of partially melted mantle rock below the edge of the Cocos plate where it moves beneath Central America. …For decades scientists have debated the forces that allow the planet’s tectonic plates to slide across the Earth’s mantle. …”One of the longer-term implications of our results is that we are going to understand more about the plate boundary, which could lead to a better understanding of earthquakes,” said Key. The researchers are now trying to find the source that supplies the magma in the newly discovered layer. See full article at http://www.nsf.gov/news/news_summ.jsp?cntn_id=127315&WT.mc_id=USNSF_51&WT.mc_ev=click.
2012 Oct 22. Italy Orders Jail Terms for 7 Who Didn’t Warn of Deadly Earthquake. By Elisabetta Povoledo and Henry Fountain, The NY Times. Excerpt: ROME — Seven prominent Italian earthquake experts were convicted of manslaughter on Monday and sentenced to six years in prison for failing to give adequate warning to the residents of a seismically active area in the months preceding an earthquake that killed more than 300 people…The verdicts jolted the international scientific community, which feared they might open the way to an onslaught of legal actions against scientists who evaluate the risks of natural hazards….
2012 Feb 13. Growth Spurt at a Bolivian Volcano Is Fertile Ground For Study. By Jean Friedman-Rudovsky, The NY Times. Excerpt: …the 43-mile-long stretch of rocky soil is now an object of international scientific fascination. Satellite measurements show that the hill has been rising more than half an inch a year for almost 20 years, suggesting that the volcano, which last erupted more than 300,000 years ago, is steadily inflating….
…Taken together with other new research … the inflation means “we could be witnessing the development of a new supervolcano,” [said Oregon State University geologist Shanaka de Silva].
Such a volcano could produce an eruption of ash, rock and pumice 1,000 times the strength of the 1980 eruption of Mount St. Helens in Washington State, the worst volcanic event in modern American history, and 10,000 times that of the Icelandic eruptions in 2010 that paralyzed global air traffic for weeks.
Luckily, while the planet has 30 to 40 supervolcanoes — 10 of them potentially active — supereruptions occur only every 100,000 years or so….
2011 Dec. Insights from the great 2011 Japan earthquake. By Thorne Lay and Hiroo Kanamori, Physics Today, page 33. On 11 March 2011, the nation of Japan and geophysicists around the world received a terrible surprise: A huge earthquake, significantly stronger than people had anticipated or prepared for in the region, struck off the northeastern shore of Honshu. Shear sliding on the fault where the Pacific Plate thrusts below Japan lasted for 150 anxiety-filled seconds, shifted the coast of Japan up to 5 m eastward, and lifted the sea floor by as much as 5 m over 15,000 km^2, an area comparable to the state of Connecticut. Displacements as large as 60 to 80 m—the largest ever measured for an earthquake—occurred near the subduction trench, and a total strain energy equivalent to a 100-megaton explosion was released during the sliding. This was the great 2011 Tohoku-oki earthquake, so-named for the region it struck. …The sudden sea-floor displacement generated a massive tsunami that swept onto hundreds of kilometers of coastline along the islands of Honshu and Hokkaidō. Tsunami waves 3–15 m high overtopped harbor-protecting tsunami walls and coastal margins and penetrated as far as 10 km inland along the coastal plain. The flood destroyed many small towns and villages, killed some 20,000 people, and initially displaced nearly half a million; six months later, tens of thousands were still living in high school gymnasiums and other temporary quarters (see PHYSICS TODAY, November 2011, page 20). …Researchers estimate its moment magnitude Mw at 9.0….
2011 Dec 5. NASA RELEASE 11-405: NASA Finds ‘Merging Tsunami’ Doubled Japan Destruction. Excerpt: NASA and Ohio State University researchers have discovered the major tsunami generated by the March 2011 Tohoku-Oki quake centered off northeastern Japan was a long-hypothesized “merging tsunami.”…
Data from NASA and European radar satellites captured at least two wave fronts that day. The fronts merged to form a single, double-high wave far out at sea. This wave was capable of traveling long distances without losing power. Ocean ridges and undersea mountain chains pushed the waves together along certain directions from the tsunami’s origin.
The discovery helps explain how tsunamis can cross ocean basins to cause massive destruction at some locations while leaving others unscathed. The data raise hope that scientists may be able to improve tsunami forecasts….
2011 June 17. From Devastation in Japan, Vital Data. By Sindya N. Bhanoo, The NY Times. Excerpt: The earthquake in Japan earlier this year was massive and devastating, but it also provided researchers with an unprecedented amount of data, thanks to Japanese investment in earthquake-monitoring technology.
Writing in the journal Nature, Japanese scientists from the Geospatial Information Authority of Japan used the data to determine that the earthquake’s slip was unusually large in comparison with its rupture area, estimated to be 150,000 by 400,000 yards….
2011 March 12. Quake Moves Japan Closer to the U.S. and Alters Earth’s Spin. By Kenneth Chang, The NY Times. Excerpt: The magnitude-8.9 earthquake that struck northern Japan on Friday not only violently shook the ground and generated a devastating tsunami, it also moved the coastline and changed the balance of the planet.
Global positioning stations closest to the epicenter jumped eastward by up to 13 feet.
…Meanwhile, NASA scientists calculated that the redistribution of mass by the earthquake might have shortened the day by a couple of millionths of a second and tilted the Earth’s axis slightly…
2010 October 18. In Studying Haiti, a New Angle on an Earthquake’s Intensity. By Henry Fountain, The New York Times. Excerpt: …A new study finds that in addition to the underlying geology, the geometry of local surface features contributed to the earthquake’s intensity as well. Susan E. Hough, a seismologist with the United States Geological Survey, and her colleagues found evidence that the shaking was amplified along a narrow ridge of hard rock south of the central city. The ridge was home to a popular hotel and other relatively well-built structures that were destroyed…
2010 June 23. NASA RADAR IMAGES SHOW HOW MEXICO QUAKE DEFORMED EARTH. NASA News. NASA has released the first-ever airborne radar images of the deformation in Earth’s surface caused by a major earthquake — the magnitude 7.2 temblor that rocked Mexico’s state of Baja California and parts of the American Southwest on April 4. The data reveal that in the area studied, the quake moved the Calexico, Calif., region in a downward and southerly direction up to 80 centimeters (31 inches). The maps can be seen here.
2010 June 16. Volcanic Eruptions in North America Were More Explosive in Ancient Past. By Cheryl Dybas, National Science Foundation. Excerpt: …The researchers found the remains–deposited in layers of rocks–of eruptions of volcanoes located on North America’s northern high plains that spewed massive amounts of sulfate aerosols into the atmosphere 40 million years ago. The scientists conducted their research at Scotts Bluff National Monument, Neb., and in surrounding areas.
…Volcanic eruptions may have significant impacts on the environment, Bao says, citing the 1991 Mt. Pinatubo and more recent Iceland volcanic eruptions.
…In the Nature paper, he and colleagues show that past sulfate aerosol formed in a different way than it does today, indicating a change from atmospheric conditions then to now.
…A similar volcanic event to the long-ago past likely will happen again, Bao says: in the next Yellowstone eruption.
…The closest analog, Bao believes, is the 1783 Laki, Iceland, eruption and the subsequent “dry fogs” in continental Europe.
…That event devastated Iceland’s cattle population. People with lung problems suffered the worst, he says.
…In North America, the very next year’s winter, that of 1784, was the longest and one of the coldest on record. The Mississippi River froze as far south as New Orleans. The French Revolution in 1789 may have been triggered by the poverty and famine caused by the eruption, scientists believe.
2010 April 29. Quake analysis rewrites history books. By Richard A. Lovett, Nature. Excerpt: A series of earthquakes that hit the North American heartland nearly 200 years ago were considerably smaller than reported in the history books, according to research presented at a meeting this week.
The quakes struck the New Madrid fault zone 200 kilometres south of St Louis, Missouri, in 1811 and 1812, long before modern seismometers allowed accurate measurements of their intensity. In the 1980s, however, some scientists estimated that the magnitudes of these quakes were over 8.0, says Susan Hough, a seismologist at the US Geological Survey’s Pasadena office in California.
…To determine the most likely magnitude of the earthquake, Hough assembled historic accounts of the shaking, and asked experts in Canada, Italy, the United States and India to estimate the magnitude of the earthquake that produced them. “There were 300, maybe 400 accounts that had to be gone through carefully,” she says.
…”The older the account and the more fragmentary, the easier it is to exaggerate,” she says. “You have an account that says people were frightened and ran outside and chimneys came down. It’s all breathless, but the bottom line may be that it was just a couple of chimneys.”
Her experts fairly consistently estimated the magnitude of the New Madrid temblors at about 7.0….
…Still, a magnitude-7 earthquake isn’t to be sneered at. “Haiti was a magnitude 7, and it’s clear what that did in a region that wasn’t prepared,” says Hough….
2010 Mar 23. Quake-Catcher Network – Laptop Computers as Earth Quake Detectors.
2009 December 23, 2009. Sun, moon tug at San Andreas fault. John Wildermuth, SF Chronicle. Excerpt: Parts of the San Andreas fault are so sensitive to stress that the faint gravitational tug of the sun and the moon may be enough to cause tiny tremors 15 miles underground, a team of UC Berkeley seismologists has found. Water under extremely high pressure apparently acts as a lubricant for the rock, allowing even the smallest stresses to cause a measurable slippage. “For the first time we’re getting a picture of what’s going on beneath where earthquakes are happening,” said Robert Nadeau of the Berkeley Seismological Laboratory, one of the authors of a report appearing Thursday in the journal Nature.
“… Unlike earthquakes, which can be large and generally short-lived jolts, the non-volcanic tremors deep underground may last for many tens of minutes at the level of a magnitude one earthquake, making them detectable only with sensitive instruments.
…Using years of readings from Parkfield and other sites, Nadeau, along with Roland Bürgmann, a UC Berkeley professor of earth and planetary science, and Amanda Thomas, a UC Berkeley graduate student, found that tremor activity varied with the effects of the sun, the moon and the ocean tides, which are driven by the moon.
…Since the strongest effects were seen when the pull of the moon and the sun was aligned with the direction of the fault’s break (Los Angeles toward San Francisco in the case of the San Andreas Fault), the researchers reasoned that water trapped deep underground was the likely explanation for the tremors, lubricating the rock to make it move easier. The tremors so far have only been found in a relatively small number of fault zones, suggesting that underground water isn’t found everywhere.
2009 April 13. Earthquakes’ Many Mysteries Stymie Efforts to Predict Them. By Kenneth Chang, The NY Times. Excerpt: Almost all earthquakes are small. A small segment of a fault, miles underground, jerks a little, the rumble imperceptible at the surface. But with a few quakes, the fault continues breaking, the ground jumps several feet and the world shakes in cataclysm.
“How does a rupture go from an inch a year to 3,000 miles per hour in a few seconds?” asked Ross S. Stein, a geophysicist at the United States Geological Survey.
No one knows.
This gap in knowledge makes earthquake prediction a frustrating and chancy exercise, and complicates the effort to calculate the risk that a human construction like a water reservoir or a geothermal power plant could inadvertently set off a deadly quake.
Last month, Giampaolo Giuliani, a technician who works on a neutrino experiment at the Gran Sasso National Laboratory in Italy, issued an urgent warning that a large earthquake was about to strike the Abruzzo region. The prediction was based on measurements he had made of high levels of radon gas, presumably released from rocks that were being ground up by the stresses of an incipient quake.
On April 6, a magnitude 6.3 earthquake hit L’Aquila in central Italy, killing almost 300 people. Mr. Giuliani claimed vindication for his prediction, which had been discounted by officials.
But earthquake experts like Dr. Stein are skeptical. Scientists studied radon as a possible earthquake warning signal as far back as the 1970s, and while they found convincing cases of radon releases before some earthquakes, …the correlations were not strong enough or clear enough for useful predictions.
…“You can’t hang your hat on it unless it’s a reliable precursor and it happens before most earthquakes and it doesn’t happen at other times,” said Susan Hough, a seismologist at the geological survey.
To complicate matters, Mr. Giuliani’s prediction was off in time and place. He had predicted that the quake would hit a week earlier in a town 30 miles away….
2009 March 19. Underwater volcano erupts off Tongan coast. The Guardian. Video: Smoke fills the sky as an undersea volcano erupts off the coast of Ha’apai in Tonga.
2009 January 16. Heads Up for Earthquakes. ScienceMatters@Berkeley, Volume 6, Issue 40. Excerpt: …Unlike hurricanes or volcanic eruptions, earthquakes can’t be forecast days or weeks in advance. The next best solution, says seismologist Richard Allen, is an earthquake early warning system. “If there was an earthquake now, we’d want to know how much it’s going to shake here, and how much time we have,” says Allen, a Berkeley professor of earth and planetary sciences.
Allen is in the process of implementing an earthquake early warning system in temblor-prone California. Called ElarmS, the system is designed to detect the imminent arrival of a strong earthquake and then warn a vulnerable public.
…the ElarmS system operates much like a spider’s silken web. An existing network of seismographs around the state continuously transmits earth movements to several central processing hubs. Just as a spider uses vibrations to judge the size and location of trapped insects, modeling programs at the centers use this ground shaking data to calculate how serious any tremor is likely to be. If the quake looks to be a whopper, the models will generate a map of the most serious shaking areas. Civil safety systems can then alert the public to the danger.
…As is, ElarmS has already proved its mettle. On October 30, 2007, just 20 days after ElarmS went online for testing in Northern California, the magnitude 5.4 Alum Rock earthquake rippled across urban San Jose. ElarmS accurately estimated the magnitude and the extent of ground shaking for San Francisco two seconds before the temblor reached city limits. Being in test mode slowed the system’s responses. If ElarmS had been running normally, the warning time would have been closer to ten seconds-long enough for most people to reach safer ground….
2008 January 17. NASA Tsunami Research Makes Waves in Science Community. Excerpt: PASADENA, Calif. – A wave of new NASA research on tsunamis has yielded an innovative method to improve existing tsunami warning systems, and a potentially roundbreaking new theory on the source of the December 2004 Indian Ocean tsunami. In one study, published last fall in Geophysical Research Letters, researcher Y. Tony Song of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., demonstrated that real-time data from NASA’s network of global positioning system (GPS) stations can detect ground motions preceding tsunamis and reliably estimate a tsunami’s destructive potential within minutes, well before it reaches coastal areas. The method could lead to development of more reliable global tsunami warning systems, saving lives and reducing false alarms. …”Tsunamis can travel as fast as jet planes, so rapid assessment following quakes is vital to mitigate their hazard,” said Ichiro Fukumori, a JPL oceanographer not involved in the study. “Song and his colleagues have demonstrated that GPS technology can help improve both the speed and accuracy of such analyses.”
…Scientists have long believed tsunamis form from vertical deformation of seafloor during undersea earthquakes. However, seismograph and GPS data show such deformation from the 2004 Sumatra earthquake was too small to generate the powerful tsunami that ensued. Song’s team found horizontal forces were responsible for two-thirds of the tsunami’s height, as observed by three
Alfred Wegener proposed the theory of continental drift – long before the idea was commonly accepted.