first_img Learning to find ‘quiet’ earthquakes Seismic noise — the low-level vibrations caused by everything from subway trains to waves crashing on the beach — is most often something seismologists work to avoid. They factor it out of models and create algorithms aimed at eliminating it so they can identify the signals of earthquakes.But Tim Clements thinks it might be a tool to monitor one of the most precious resources in the world — water.A graduate student working in the lab of Assistant Professor of Earth and Planetary Sciences Marine Denolle, Clements is the lead author of a recent study that used seismic noise to measure the size and water levels in underground aquifers in California. The technique could even be used to track whether and how aquifers recharge following precipitation, and understand geological changes that might occur as water is pumped out. The study is described in a published paper in Geophysical Research Letters.“The way this would commonly be done today would be to take a measurement at a groundwater well,” Clements said. “And if you have a network of those wells, you can develop a model where you assume a number of hydrological parameters … and that allows you to measure the health of the aquifer.“But what we showed is we can just directly measure these waves that are traveling through the entire aquifer. So we don’t have to make those assumptions,” he said.,Using seismic noise, researchers were able to measure the water level change of the San Gabriel Valley aquifer, just outside Los Angeles, to within a centimeter.A massive drought over the past five year was one reason researchers chose to focus on the San Gabriel Valley.“We estimated [the water-level change] at about half a cubic kilometer,” Clements said. “And that’s exactly what the San Gabriel water master said they pumped out during the drought to meet demand. “There are over 1 million people who live in this relatively small area outside Los Angeles who depend on the groundwater for all their water-use needs. So our goal was to understand if we can use seismic waves to understand what’s happening with the aquifer.” — Tim Clements While the study wasn’t the first to hit upon the idea of using seismic noise to study groundwater, Denolle said earlier efforts were hampered because they relied on a signal that was relatively weak in comparison to environmental factors like temperature and pressure.“This was a large signal we looked at,” she said. “The aquifer oscillated with 20 meters of water-height changes in a couple years, so it’s a bigger signal than any environmental influence.”The system could also be a useful tool for anyone involved in water resource management, Clements said, because it can give them a moment-to-moment view of precisely what is happening underground.“In this study, we looked at about 17 years of data, from 2000 to 2017, but going forward this could be used in a water-management application, so you could get a picture of what’s happening with the aquifer on a daily basis,” Clements said.Aside from providing groundwater measurements, the technique can be used to monitor the health of an aquifer over time.“If we had the data, we may be able to use this technology to look back at what aquifers looked like in the past and study the long-term evolution of an aquifer,” Denolle said. “One of the challenges for people who manage water resources is whether aquifers still respond elastically, meaning can we recharge it with the same storage capacity or is it losing capacity over time as we pump water out? Using seismic waves, we can potentially find out whether these aquifers are elastic or not.”Going forward, Clements said he plans to pursue ways to improve the resolution of the system at both the micro and macro levels.Working in collaboration with faculty at Tufts University, he installed wells and seismometers on campus to track changes as groundwater is pumped to the surface to irrigate sports fields. Other efforts are focused on using the existing seismometer network in California to improve ways to measure the overall size of aquifers.This research was supported with funding from Harvard University. “There are over 1 million people who live in this relatively small area outside Los Angeles who depend on the groundwater for all their water-use needs,” Clements said. “So our goal was to understand if we can use seismic waves to understand what’s happening with the aquifer.”center_img Researchers create algorithm that can separate small disturbances from seismic noise Relatedlast_img read more

first_imgTwo DOF ASA subsidiaries have been awarded contracts for the Skandi Commander vessel and one ROV.DOF said on Friday that the deal for the Skandi Commander, awarded to DOF Subsea Brazil and Norskan Offshore, had a duration of 150 days.According to the company, the work under the contract will start in April 2018.The Skandi Commander is an MT 6009 Design RSV vessel built in 2007, reflagged to a Brazilian flag in 2017. The vessel joined the DOF fleet as a platform supply vessel but has since been refitted to feature construction support capabilities and is now in Brazilian waters.It is worth mentioning that DOF ASA and DOF Subsea have already won two separate sets of deals this week.DOF announced on Thursday that it had won deals for the Skandi Foula, Skandi Rona, Skandi Feistein, and Skandi Saigon vessels as well as a deal with Nexen for the support of the COSLPioneer rig hook-up operations.Furthermore, DOF Subsea won contracts in the Atlantic region for the Skandi Neptune, Geosund, and Skandi Constructor vessels as well as a four-year global frame agreement for the provision of survey and positioning services on third-party vessels.Offshore Energy Today Stafflast_img read more

first_imgNZ Herald 22 July 2015At first glance, the profiles seem innocent enough. There’s Lucy, 31, from Rochester, who enjoys cooking, theatre and books, and Jack, 46, from Hampshire, who describes himself as a “laid-back character who travels a lot with work and loves music and sport”.Some of the requests even sound rather sweet. Matthew, a 59-year-old Londoner, hopes to meet a woman to “chat about life in general, politics, faith and social justice”, while Sally, 43, from Hertfordshire, wants “someone to keep me on my toes and make my pulse race”.They could all be hopefuls on an ordinary dating website – one of the many that have sprung up in recent years to help single men and women find love through the internet.But these profiles are far more sinister than that. For the people behind them are all, in fact, married. They are signed up to Ashley Madison, a controversial website that promotes and caters for extra-marital affairs.One can only imagine the huge wave of terror felt by them yesterday when a group of hackers threatened to reveal the identities of Ashley Madison’s members.One of the site’s many opponents, a secretive group calling themselves The Impact Team, claim to have hacked into the online database and stolen the details and private messages. They warn that unless the site is shut down with immediate effect, they will expose its 37 million cheating users worldwide by publishing their names, addresses and explicit images online. read more

first_imgThe highly-touted young Kiwi can play back row or centre and showed off his silky ball skills in a tight 16-12 loss to the Dragons last Saturday with a lovely pass to create Michael Chee Kam’s maiden NRL try – and set up a grandstand finale with the fast-finishing Tigers falling just short of knocking off the third-placed Dragons.Speaking to after the game, Marsters said while he’s been playing 80 minutes as a centre in reserve grade he’ll take whatever chance coach Ivan Cleary affords him in the top squad.”As a kid you always want to make your NRL debut. That was one of my goals. I really enjoyed it out there and just want to build on the performance,” Marsters said.After Cleary pulled him aside at training last Wednesday to inform him of his impending debut, Marsters said he rang around whatever family he could to get together so he could tell them at the same time. Some flew over from New Zealand to watch his debut.”I rang all my family members to tell them to come home, got them in a bunch and let them know and they were all pretty excited for me,” he said.”I had some family fly over from New Zealand to come watch me play; that was pretty important for me.”It was pretty tough, it was pretty fast out there but the boys stuck with me, they were talking to me on the edge and I sort of found my rhythm.”Hopefully if I get the chance to play next week I take it with two hands.”An early hamstring injury to veteran back-rower Chris Lawrence meant Marsters was called on to play more minutes than he would have expected, eventually finishing with 13 tackles, 88 running metres and a try assist in 43 minutes on field.”I want to build my minutes, I want to be able to play 80,” Marsters said.”Chris Lawrence, it’s a sad thing for him to go down like that but I want to knuckle down and get better as a player.”I’ve been playing centre in [the Intrust Super Premiership], I haven’t played back row for a while but I’ll play anywhere Ivan wants me to play. There’s an opportunity there for me to play back row so I want to take it with both hands and see where it goes.”I don’t mind, either way, Ivan knows what’s going on, I just want to perform for him.”And the magic ball to Chee Kam?”He was calling for it, I should have gone open but I heard him calling so I gave him the ball and he scored a pretty good try,” Marsters smiled.Photo by:  Robb Cox. Copyright: NRL Photos. (Wests Tigers rookie Esan Marsters impressed on debut against the Dragons).last_img read more