Maitri

Info

• Open-Access
• Journal: The Leading Edge
• Source code: pinga-lab/nmo-tutorial
• doi: 10.1190/tle36020179.1

About

This is a part of The Leading Edge tutorials series. All tutorials are open-access and include open-source code examples.

The manuscript was written in Authorea. You can view and comment on the text online at Authorea and even edit it on the SEG Wiki. The final (pretty) PDF version is free to download from the publisher website (follow the doi link).

The Jupyter notebook that accompanies the tutorial (see the source code repository on Github) contains the full source code, along with documentation and tests. Both figures of the tutorial are produced by the code in the notebook.

The code and idea for this tutorial came from my Geofísica 2: Sismologia e sísmica course. I came across the problem of implementing NMO correction while preparing my lecture and practical exercises on this topic. This is a clear example of how learning happens both ways in a classroom.

Abstract

Open any text book about seismic data processing and you will inevitably find a section about the normal moveout (NMO) correction. When applied to a common midpoint (CMP) section, the correction is supposed to turn the hyperbola associated with a reflection into a straight horizontal line. What most text books won't tell you is how, exactly, do you apply this equation to the data?

That is what this tutorial will teach you (hopefully).

Citation

Uieda, L. (2017), Step-by-step NMO correction, The Leading Edge, 36(2), 179-180, doi:10.1190/tle36020179.1

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The latest version of the World Stress Map Project has been officially released this week. This is the 30^th anniversary of the project, and sees a big boost in data over the prior release in 2008. The latest version of the World Stress Map contains 42870 stress data records, which is approximately double that of the prior release, and about 10 times more than the first release over 25 years ago.

The 2016 Release of the World Stress Map

The World Stress Map Project started back in 1986, and was the brainchild of Professor Karl Fuchs and the International Lithosphere Programme, who asked Mary-Lou Zoback to head up a 5-year global effort to map out the state of tectonic stress in the Earth’s lithosphere. The initial results from over 30 researchers were published in an awesome 1992 issue of the Journal of Geophysical Research. Karl Fuchs and the WSM deputy leader, Dr Birgit Muller, then managed to get the project continued through the Heidelberg Academy of Sciences, with a research team based in Karlsruhe running the project until 2008. This phase of the project culminated in a 2010 special issue of Tectonophysics. Since 2008, the project has been based at the GeoForschungsZentrum in Potsdam, and led by Professor Oliver Heidbach, and is a part of the ICSU World Data System. The project remains a huge global collaborative effort, with contributions from dozens of researchers.

Where Disaster Strikes: Modern Space and the Visualization of Destruction, an exhibition of disaster maps, is taking place now until 19 April at Harvard’s Pusey Library.

Floods, fires, earthquakes, volcanoes, bombings, droughts, and even alien invasions: disaster can take many forms. And, although disasters are always felt dramatically, a disaster’s form and location impacts who records its effects and what forms those records take. “Where Disaster Strikes” investigates the intertwined categories of modern space and disaster through the Harvard Map Collection’s maps of large destructive events from the London Fire to the present.

Open to the public. The exhibition also has a substantial online presence.

As the holiday season has progressed I’ve spent a bunch of time in the car, traveling three hours at a crack to see friends and family in various parts of Midwestern USA. Much of that travel has been alone, my family having decided to ensconce themselves with my in-laws for the full duration of the […]

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Another book I missed at the time of its publication: Charles Drazen’s Mapping the Past: A Search for Five Brothers at the Edge of Empire (William Henemann, August 2016). It’s a family history: Drazin’s grandfather and brothers were military surveyors from rural Ireland “who travelled around the world as officers in the Royal Engineer Corps—surveying, exploring, mapmaking, fighting— in the twilight years of the British Empire.” [WMS]

Randall Munroe is a bad man who is back with another bad map projection to make our eyes bleed. (If he does this often enough he’ll have enough for a book. Heaven forfend.) This one is, like his other maps, fiendishly subtle: it stretches and compresses countries to fit where their time zones ought to be, longitudinally speaking.

I sent this to the governor of Colorado, John Hickenlooper today, after seeing the AP story about a Trump administration draft memo regarding mobilization of the National Guard to be used to round up undocumented immigrants. Yes, I am aware that we’re talking a draft, but I find it seriously horrifying that this is even being talked about as an option, however off-handedly or unseriously. This is not a thing you fucking joke about.

Anyway, that prompted me to write and send the following message today. I’m sharing it in the hope that others will feel encouraged to send similar messages.

#

Dear Governor Hickenlooper:

Per the Associated Press today, a draft memo from the Trump Administration showed they’re thinking about using the National Guard to round up undocumented immigrants. Considering the absolutely tragic and shameful history of our own state when it comes to the National Guard being mobilized against our citizens and residents (i.e.: the Ludlow Massacre), this calls on us all to speak firmly against this notion before it can gather steam.

Beyond that, undocumented immigrants are a vital part of Colorado society. It would be far better if they could have a path to legal citizenship or permanent residency, but lack of national will does not change the enormous contributions they make to Colorado daily. We should be respecting and protecting all of our residents, whether they have papers or not.

I urge you to speak out in strong support of undocumented Coloradans, and do everything in your power to keep their families from being torn apart by these unfair and racist policies we keep seeing from Washington DC. Make us a sanctuary state; while I know we can’t stop ICE, we can refuse to aide and abet the destruction of families and the victimization of innocent people who are integral to the fabric of Colorado.

With a lack of national will, it falls to us to step up and show our strength of spirit and compassion. I know Colorado is better than what our national government is currently trying to become.

Thank you.

A Houston Jewish community center became the latest target of slew of coordinated bomb threats across the country, which have come in waves on a regular basis since January. Around 10 a.m. Monday, the Evelyn Rubenstein Jewish Community Center received an anonymous call from a person threatening to blow up...

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Democracy is not a given. The Greeks experimented with it. Then it faded into oblivion, only to return many centuries later. Nowadays, democracy structures much of our modern world. But could it do a disappearing act again? If there’s enough complaceny and duplicity, you can’t rule it out.

All of this is to say, it’s a good time to think about democracy and its alternatives. And to do that, you can spend time with Yale University’s free course, Introduction to Political Philosophy. Taught by professor Steven B. Smith, the course covers the following ground:

This course is intended as an introduction to political philosophy as seen through an examination of some of the major texts and thinkers of the Western political tradition. Three broad themes that are central to understanding political life are focused upon: the polis experience (Plato, Aristotle), the sovereign state (Machiavelli, Hobbes), constitutional government (Locke), and democracy (Rousseau, Tocqueville). The way in which different political philosophies have given expression to various forms of political institutions and our ways of life are examined throughout the course.

You can watch the 24 lectures from the course above, or find them on YouTube and iTunes. To get more information on the course, including the syllabus, visit this Yale website.

The main texts used in this course include the following. You can find them in our collection of Free eBooks, or purchase copies online.

• Plato, Trial and Death of Socrates
• Plato, Republic
• Aristotle, Politics
• Machiavelli, The Prince
• Thomas Hobbes, Leviathan
• John Locke, Second Treatise of Government
• Jean-Jacques Rousseau, Political Writings
• Alexis de Tocqueville, Democracy in America

Introduction to Political Philosophy will be added to our collection, 1200 Free Online Courses from Top Universities. There you can find a specialized list of Free Online Philosophy Courses.

Follow Open Culture on Facebook, Twitter, Instagram, Google Plus, and Flipboard and share intelligent media with your friends. Or better yet, sign up for our daily email and get a daily dose of Open Culture in your inbox. And if you want to make sure that our posts definitely appear in your Facebook newsfeed, just follow these simple steps.

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Sometimes goal setting can lead to a narrow focus that may lead you to limit yourself and miss opportunities. Just ask cab drivers.

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Swastikas spray-painted on fences and signs in Sienna Plantation. Students saluting Adolf Hitler during Cypress-Ranch High School's senior class picture day. Racist and anti-Semitic  fliers distributed at universities and in neighborhoods across Harris, Fort Bend and Montgomery counties. All of that happened in just one week, leading the Anti-Defamation League's...

After watching Ava DuVernay’s 13th, a deep dive into America’s broken prison system and how it’s a new form of slavery, you should definitely check out the documentary I Am Not Your Negro. Narrated by Samuel L. Jackson, the film is based on activist James Baldwin’s unfinished book Remember This House, and it explores racism in America through his recollection of civil rights leaders Malcolm X, Medgar Evers and Martin Luther King, Jr.

The clip above, titled “Segregation,” perfectly explains how a white person who has black friends or is really nice to their black maid doesn’t automatically mean they’re not racist. As he recalls in the video, his friends would invite him other to their house but never came to his. They were segregated not just in school, but in life because that white friend doesn’t know his experience outside of their limited interactions. “I’m sure they have nothing against Negroes [but] that’s really not the question,” Baldwin says. “The question is really a kind of apathy and ignorance.”

Basically, just because one isn’t burning crosses on their black friend’s lawn doesn’t mean they can’t be racist. For those with a black friend who refuse to visit that person’s neighborhood or are uninterested in hearing about their experiences, the question to ask yourself is why.

(image via screencap)

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Excerpts from an article on Quanta Magazine, rearranged for clarity and space: Math conferences don't usually feature standing ovations, but Francis Su received one last month in Atlanta. In his talk he framed mathematics as a pursuit uniquely suited to the achievement of human flourishing, a concept the ancient Greeks called eudaimonia, or a life composed of all the highest goods. Su talked of five basic human desires that are met through the pursuit of mathematics: play, beauty, truth, justice and love. Su opened his talk with the story of Christopher, an inmate serving a long sentence for armed robbery who had begun to teach himself math from textbooks he had ordered. After seven years in prison, during which he studied algebra, trigonometry, geometry and calculus, he wrote to Su asking for advice on how to continue his work. After Su told this story, he asked the packed ballroom at the Marriott Marquis, his voice breaking: "When you think of who does mathematics, do you think of Christopher?" If mathematics is a medium for human flourishing, it stands to reason that everyone should have a chance to participate in it. But in his talk Su identified what he views as structural barriers in the mathematical community that dictate who gets the opportunity to succeed in the field -- from the requirements attached to graduate school admissions to implicit assumptions about who looks the part of a budding mathematician. When Su finished his talk, the audience rose to its feet and applauded, and many of his fellow mathematicians came up to him afterward to say he had made them cry. [...] Mathematics builds skills that allow people to do things they might otherwise not have been able to do or experience. If I learn mathematics and I become a better thinker, I develop perseverance, because I know what it's like to wrestle with a hard problem, and I develop hopefulness that I will actually solve these problems. And some people experience a kind of transcendent wonder that they're seeing something true about the universe. That's a source of joy and flourishing.

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The word “alternative” appears both in the fun new craze sweeping the government (“alternative facts”) and in a few science fiction staple ideas (“alternate history” and “alternate universe,” for example). Despite that superficial similarity, legendary scifi author Ursula K. Le Guin wants to make sure no one confuses…

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William Smith’s 19th-century geological maps of Britain are now available online via an interactive map interface. [Maps Mania]

The Harvey Wallbuilder

Vodka, orange juice, and Galliano L’Autentico, garnished with an IOU from Mexico.

Twittertini

140 ounces of all caps, exclamation points, and petty complaints. Best served at 3 AM with typos.

A Shot of Bannon

Mix pure evil, bad skin, rheumy eyes, and domestic abuse with white nationalism and fascism. Stir until you develop Cirrhosis of the Soul.

Muslims Go! Mojito

Create the most delicious, welcoming drink 200 years ago. Then decide in 2017 that it’s for Christians only. Sorry!

Gin and Panic

Gin consumed directly from bottle while sitting in a dark closet reading news alerts on iPhone.

Bloody Mary Bleeding Out of Her Wherever

Tomato juice and vodka, served with a jumbo tampon that was not procured at a local Planned Parenthood office.

Omarosa Mimosa

Bitter orange juice mixed with the only black liqueur the orange juice has ever tolerated.

Grab the Pussy on the Beach

A short-fingered pour.

Pre-existing Condition on the Rocks

Crushed Tylenol dropped into a large glass of whiskey. This is also now your Primary Care physician.

Alternate Factarita

Lime juice, with enough tequila to make you forget that you lost the popular vote and then declared yourself Bartender of the World.

St. Petersburg Ice Tea

Send email to your mother on a private server asking for recipe. Answer will be sent to you from a “Mrs. Nice Lady American Person Who Is Not Spy.”

The Kellyanne Cosmo

Vodka, Triple Sec, and not even a splash of compassion or morality. Prepare while wearing a garish red, white, and blue Teddy Bear costume.

White Russian Election Rigger

Coffee-flavored liquor and ice. Sip while simultaneously giving Putin his massage and Assange his foot rub.

The Really Really Old Fashioned

Bourbon on the rocks. Add a splash of Jeff Sessions bitters, then enjoy while the women are in the kitchen barefoot and pregnant.

Hot Toddy Planet

Whisky, honey, and enough hot water to melt all the glaciers that aren’t really melting because climate change is a myth, you liberal moron.

Nuclear Sunrise

Tell dancing fool/Secretary of Energy Rick Perry to put tequila, OJ, and grenadine syrup in a blender, then accidentally push the red button for the nuclear arsenal instead of the mix button. You’ll never know what hit you!

EA Sports' 'Madden' games have correctly predicted the Super Bowl's outcome nine out of 13 times. How? Data. The post How Madden Got So Silly Good at Predicting Super Bowl Winners appeared first on WIRED.

In a lengthy Rolling Stone feature, Depeche Mode announced its new album Spirit, which is coming March 17, and released the record’s first single “Where’s The Revolution?” In the interview Depeche Mode vocalist David Gahan says Spirit isn’t expressly political, but that theme seems to appear time and again. “I don’t listen to music in a political way,” said Gahan, “But it’s definitely about humanity, and our place in that.” Those humanist and quasi-social themes are evident on “Where’s The Revolution?,” a song that Gahan claims was written by the band’s chief songwriter Martin Gore in “a very sarcastic, English way.” That can be seen in the song’s chorus which reads, well, a little odd. Gahan sings, “Where’s the revolution? / Come on people, you’re letting me down” at a time when people in America are regularly organizing and activating, but ...

Elon Musk has long said that artificial intelligence will have to augment human abilities, rather than compete with them, in order to avoid a portentous future. He has been active in trying to find ways to evaluate and reduce potential risks posed by AI. From a report: On Monday, Musk tweeted out a set of principles for AI research and development created by a group of scientists at a recent conference for the Future of Life Institute (of which Musk is a board member). Musk said in response to a comment that ensuring AI augments human abilities is "critical to the future of humanity." Musk recently told a Twitter user that there may be an announcement "next month" regarding such as device, which Musk has called, in the past, a neural lace.

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"What is the precise moment, in the life of a country, when tyranny takes hold? It rarely happens in an instant; it arrives like twilight, and, at first, the eyes adjust."

The New Yorker's Evan Osnos, with one of the best essay openings of the year, examines the posthumous memoir of Xu Hongci, a Chinese revolutionary and true believer of Mao Zedong, later imprisoned.

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Kirby Ferguson, who created the remarkable Everything is a Remix series, has a new podcast hosted by the Recreate Coalition called Copy This and he hosted me on the debut episode (MP3) where we talked about copying, creativity, artists, and the future of the internet (as you might expect!). (more…)