At 2:46 Monday afternoon, Japan went quiet.
In memory of the lives lost two years ago in the earthquake that struck at that hour and the tsunamis that followed, a moment of silence was held across the country. From government buildings to small coffee shops, everyone paused -- the Emperor of Japan, politicians, national TV anchors, office workers. In Tokyo the busy subways were shut down briefly, and in some areas drivers pulled over to the side of the road.
At the same time on Twitter, an argument broke out.
At exactly 2:46 many users posted "Mokutou," Japanese for "silent prayers," followed immediately by angry responses along the lines of "You're not praying silently if you tweet about it," and a lengthy online back-and-forth ensued.
The 2011 earthquake and tsunami are forever linked with social media in Japan. In the chaotic days and weeks that followed, with the northeast coast in shambles and hundreds of thousands in shelters with no phone service, many turned to services like Twitter and Facebook to post personal news or keep in touch.
The surge in use drove such sites into the mainstream, where they have remained since. Japanese users that had long been unwilling to use their real names online, sticking to local anonymous networks like Mixi, were suddenly revealing the names of dead relatives and posting pictures of their ruined homes.
"People had lost their homes and families, but they wanted to keep track of what was happening," said Hatsue Toba, a 51-year-old who survived the tsunami in the coastal town of Rikuzentakata, much of which was flattened by a tsunami.
Many residents left the area, but Toba stayed in town and started a small vegetable shop to help local farmers recover.
"At first people didn't have computers, but they could use the Internet with their phones," she said.
Toba made a Twitter account in June and one on Facebook in December, and is still active on both today. Her daily "Good morning" posts are famous among former residents scattered across the country, and her vegetable store became a meeting place when they returned to visit.
Minako Miyamoto, a nurse who lives in the unaffected city of Kanazawa on the western coast of Japan, rushed east to volunteer when she learned how serious the local situation was, and eventually launched a nonprofit to help.
"Before the disaster, I used Mixi, Facebook, and Twitter. But on Mixi, many people are anonymous, while on Facebook people use their real names, so it is more trustworthy," she said. "Even now, I use Facebook to keep in touch with people I met in the shelters."
Statistics show that users of both services have surged since March 2011. In February of that year, Twitter was averaging about 130 million messages a day in Japan, a number that has since climbed to 400 million. The company declined to provide exact user numbers for the country, but Japanese users are among its most numerous and active.
"There was a seven or eight-fold increase in tweets overnight after the earthquake," said Twitter spokeswoman Kaori Saito in Tokyo. "Some people had trouble finding reliable information, so we've tried to make it easier to search for accounts run by local governments."
Last year Twitter created "lifeline" accounts operated by local Japanese towns and cities, which users can search for using their postal codes. The company has held "disaster drills" to help users tweet useful information during emergencies, and Japan's Fire and Disaster Management Agency is mulling allowing "911" calls to be placed through Twitter when phones go down.
The sheer number of Twitter messages sent out during and after a disaster can also serve as a source of data. Researchers at the University of Tokyo have said they can detect when earthquakes are occurring with 96 percent accuracy by filtering Twitter messages for certain keywords and frequency.
Google also became a trusted online source in the months after the quake. Its "Person Finder" site became the national database for information on those caught in the disaster and eventually swelled to over 600,000 entries. The site was repeatedly featured by national broadcaster NHK as a public resource and received data from the National Police Agency, local governments and newspapers. Google has since launched services such as "public alerts" that allow users to quickly find local info on earthquakes and other disasters.
The search giant, Twitter and other online companies have pledged to work more closely in future disasters. In September of last year Google helped organize a "big data workshop" to analyze information from the 2011 earthquake. Google provided data on search trends and Twitter supplied a week of Twitter messages from after the disaster. Honda supplied data such as car location information from its online navigation system.
Facebook is still not as popular in Japan as in other countries and has faded in recent months. But the number of accounts increased about six times since before the earthquake and is currently between 13 million and 14 million, according to an analysis published by Japan's Ceraja Technology and Socialbakers in the U.S.
Many of the government support agencies and nonprofit agencies that sprung up in the aftermath of the disaster say they use Facebook as their main portal to reach users.
"At the time [after the earthquake] Facebook was the way we kept in touch privately. People couldn't use their phones, and it was the easiest," said Takahiro Chiba, an official who organizes volunteers in the eastern seaside town of Kessenuma, where tsunamis washed huge ships ashore and caused massive oil fires.
"Now it's more for public groups, for posting notices and information about our activities. Volunteers are still coming, and this is how we reach them."
Some new social networks were born out of the disaster. Line, a Japanese chat app that launched in June of 2011, is now common in the country and hit 100 million users in January of this year, with another 3 million signing on each week.
"People were looking for a way to communicate and had trouble doing so with mobile calls and email," said Jun Masuda, the executive in charge of the service's strategy and marketing.
The disasters that hit Japan's northeast coast in 2011 were a human tragedy. The earthquake and tsunamis left over 17,000 dead or missing, with 310,000 still in temporary housing, many unable to return home because of radiation concerns related to meltdowns at the Fukushima Daiichi nuclear power plant.
In the aftermath, services like Facebook and Twitter surged in users and have become part of Japanese society. Even so, some have started to wonder if there are other, better kinds of social networks.
"I have 800 friends on Facebook, but I think that less than half of them see what I'm saying," said Miyamoto, the volunteer nurse. "Lately I've realized I need to create more events where people get together in the real world."