"Youthquake” (also spelled “youth quake") was defined in the September 1965 Ebony magazine:
“They champion what is known as ‘Youthquake,’ which means super, boss, and a gas. It reflects the tempo of the times in music, dress and dance, and serves as the password for today’s turned-on generation.”
“Youthquake 1965” appeared in the January 1965 issue of Vogue magazine, and editor-in-chief Diana Vreeland is often given credit for coining the word. British fashion designer Mary Quant—who popularized the miniskirt and hot pants—is also frequently given credit for coining “youthquake.”
The term “youthquake” is associated with the 1960s, but was repopularized in the 2010s. Teen singing star Justin Bieber was said to have caused “youthquakes.” Revolutions by Muslim youth in the Middle East and North Africa in 2011 caused Time magazine in its February 17, 2011 issue to publish a story titled “Inside the Arab Youth Quake.”
Wikipedia: Youthquake (movement)
Youthquake was a 1960s fashion, musical and cultural movement. The term was coined by Vogue‘s editor-in-chief Diana Vreeland in 1963. London was the center of this movement. Teenagers dominated the fashion and music scene. The fashion of youthquake was fun, spirited and youthful – miniskirts and jumpsuits. Poster girls of the youthquakers such as Jean Shrimpton, Twiggy, Penelope Tree, Veruschka, and Edie Sedgwick were often on the cover of fashion magazines such as Vogue.
Mary Quant and Betsey Johnson were named as some of the fashion designers at the helm of the youthquake movement. Andy Warhol and his muses were also seen as part of the youthquake movement. Electronic artist, Alphabet Pony, makes reference to Edie Sedgwick, in his 2009 release, ‘Youthquake’.
(Oxford English Dictionary)
Etymology: < youth n. after earthquake n.
The series of radical political and cultural upheavals occurring among students and young people in the 1960s.
1967 Punch 8 Nov. 708/2 Mary Quant opened her first Bazaar shop‥simultaneously with the first tremors of the youthquake.
1970 R. Neville Play Power 18 A unique feature of today’s Youthquake—as Vogue once dubbed it—is its intense, spontaneous internationalism.
1976 Sunday Mail (Brisbane) 5 Sept. 19/3 He’s built an empire based on the youthquake.
Conde Nast Archive Blog
A New Era in Vogue Fashion: Youthquake 1965
September 21, 2009 10:54 pm
“There is a marvelous moment that starts at thirteen and wastes no time. No longer waits to grow up, but makes its own way, its own look by the end of the week. The dreams, still there, break into action: writing, singing acting, designing. Youth, warm and gay as a kitten yet self-sufficient as James Bond, is surprising countries east and west with a sense of assurance serene beyond all years.
First hit by the surprise-wave, England and France already accept the new jump-off age as one of the exhilarating realities of life today. The same exuberant tremor is now coursing through America – which practically invented this century’s youth in the first place.
The year’s in its youth, the youth in its year. Under 24 and over 90,000,000 strong in the U.S. alone. More dreamers. More doers. Here. Now. Youthquake 1965.”
 Vogue January 1, 1965. 112
8 May 1965, Delaware County Daily Times (Chester, PA), TV listings, pg. 8A, col. 3:
TV 10 Reports—“Youthquake”
4 June 1965, New York (NY) Times, “College Girls Are Paraded and Feted While Magazines Pick Their Brains” by Angela Taylor, pg. 24, photo caption:
Glamour magazine threw its annual party Wednesday night at Roseland for the 10 Best-Dressed College Girls who will appear in the August issue. A crowd of more than 2,000 paid $15 each for charity and to see a wild “Youth Quake” show.
22 August 1965, New York (NY) Times, pg. SMA16 ad:
Why did they choose it for this “Youthquake” dress? Because nothing stays as new as Durene.
September 1965, Ebony, pg. 158:
‘Youthquake’ Creation To Highlight Big Show
Most of these designers have chosen to stay with the conventional, but some, like Mary Quant, have sounded the countdown, and are already off in space. They champion what is known as “Youthquake,” which means super, boss, and a gas. It reflects the tempo of the times in music, dress and dance, and serves as the password for today’s turned-on generation.
2 September 1965, New York (NY) Times, “Models Go-Go—and So Do Fashions” by Virginia Lee Warren, pg. 35:
Yesterday it was Best’s turn to present what was called a Youthquake—live rock ‘n’ roll, along with whirling, capering models in clothes by Mary Quant, who started the whole mod movement in London eight years ago, and by Tuffin & Foale, younger both in years and experience.
21 October 1965, New York (NY) Times, pg. 16 ad:
For Puritan is a giant of fashion, with many divisions creating lovely things for you. Newest...and newsiest...is Puritan’s “Daphne”, stirring up a Youth-quake wherever it appears.
(Puritan Fashions Corp.—ed.)
Justin Bieber: Never say never
February 11th, 2011 10:03 am ET
I am not a fan of Justin Bieber but I do recommend this movie. Now I know why there is such a ‘youthquake’ with this kid.
Thursday, Feb. 17, 2011
Rage, Rap and Revolution: Inside the Arab Youth Quake
By Bobby Ghosh
New York City • Government/Law/Politics/Military • (2) Comments • Wednesday, March 09, 2011 • Permalink
i am justin bieber’s fan! this movie is fabulous!i watched twice already.lol
i like it! thanks!justin bieber is cute!