The first wave of terror struck shortly before 3 p.m. on a Friday.
"The ground, the thing that doesn't move, was moving," recalled Tomoko Sudo, who was at work when the magnitude-9.0 earthquake hit Japan last year. "It felt like it was a living creature."
Then the second shock hit: She couldn't reach family members for days in some of the hardest-hit regions in the disaster that caused some 16,000 deaths. So Sudo, 28, turned to Google's Person Finder, which the company's engineers had up and running within two hours after the shaking stopped.
The service, created after the 2010 Haiti earthquake, is a tool to help track down the missing after a disaster.
When the earth convulsed that March day, the Internet was for millions of Japanese the only link to critical information and to one another. Google, Twitter, Cisco Systems and other technology companies were thrust into the role of technological first responders, underscoring a new dimension to the services offered by Silicon Valley tech companies as the Internet becomes ubiquitous and is often more reliable than other communications systems.
One by one, Sudo tracked down loved ones, including a cousin whose house was swept away by the tsunami. She said she was "shivering" with joy as she got word that they were all right.
This help, said Gisli Olafsson, emergency response director at NetHope, a nonprofit that promotes collaboration between major tech companies and global aid organizations, is worth much more than corporate cash donations.
"You have really smart people working on really difficult problems," Olafsson said. "That becomes extremely valuable."
Google employees, themselves shaken up by the quake and their inability to reach family members, immediately set about deploying services for a traumatized nation from the company's Tokyo high-rise headquarters. Some worked on their laptops throughout the night.
"It was all about the crisis, all about finding people," said Hiroya Isa, a marketing manager at Google Japan.
In addition to revving up Person Finder, engineers worked to publish data on traffic problems, road damage and train delays on Google Maps.
"Tens of thousands of people were walking along the streets," recalled Ryan Falor, a Mountain View, Calif.-based engineer who worked around the clock after the quake hit to assist his colleagues in Japan. "We did not know why roads were blocked but we knew cars were not moving."
While Google Maps helped Japanese navigate through the disaster zone, Twitter became the de facto communication tool for many. Unable to make phone calls, Japanese sent tweets to each other because Internet networks - while at times slow - were up and running.
Masahiko Inami, a professor of media design at Keio University in Tokyo, relied on Twitter and Google Maps to make his way home by foot, finally arriving at 3 a.m. "Social media is very robust in dangerous situations," he said.
U.S. Ambassador John Roos used Twitter to communicate with Americans in Japan during the disaster and, upon learning of about 80 people trapped in a hospital, alerted authorities, who assisted them. "It was incredibly effective," he said of Twitter.
Cisco Systems, meanwhile, sent in networking gear and other equipment that was deployed in and around the worst-hit areas, establishing instant service for emergency personnel.
The efforts of these companies did not go unnoticed. Google and Twitter, for example, have made significant market gains in Japan since the disaster.
Google's market share spiked from 49.2 percent in March 2011 to 54.6 percent in August 2012, according to Internet analytics company ComScore. The number of monthly visitors to Twitter Japan jumped from 19.5 million in March 2011 to 21.8 million in August 2012, even as its closest competitor in the country, Mixi, dropped from 18.3 million visitors to 12.5 million during the same time span.
Since the earthquake, Google has been embraced by the Japanese business community and is seen as more than a global technology behemoth, said Mak Arima, Google's Japan managing director. "(Japanese) have told me, 'Now, we can see your face more clearly than before.' "
The Japanese government is considering standardizing Twitter's use for emergency communications.
Japan was probably the first industrialized nation to be hit with a catastrophic disaster in which social media played a major role because most people are equipped with Internet-enabled mobile devices, said James Kondo, who heads up Twitter's Japan operations. But lessons learned here will be valuable elsewhere, he said. "This is not a Japan solution, but a global solution."
The ubiquity of the services made them an instant lifeline in Japan.
Person Finder became an instant sensation as Japanese frantically searched for loved ones. The service allows those desperately looking for loved ones to create entries about them in a searchable database. The entries can be accessed and updated by others as information about family members and friends comes to light. So even if those looking for loved ones could not contact them directly, many were able to get information on the well-being and whereabouts of family and friends from Person Finder updates, sometimes supplied by strangers.
Shortly after launching Person Finder, Google asked people to take pictures of handwritten posters at evacuation centers and upload them on Google's Picasa online photo-sharing service. Google employees, who transcribed the names from the photos onto Person Finder, were quickly overwhelmed.
"It was almost out of control," recalled Google engineering manager Hideto Kazawa.
Within weeks, 10,000 photos were uploaded onto Picasa and some 5,000 volunteers from around the world pitched in to transcribe the names onto Person Finder. In the end, more than 140,000 names were entered into Person Finder, which was accessed by more than 600,000 users.
Satoru Kikuta, a Tokyo computer engineer, used Person Finder to search for 40 friends and family in his home city of Kesennuma along the northeastern coast of Japan, where the tsunami left bodies strewed on streets and boats perched precariously in the center of town.
Kikuta, who passed along information to family members about loved ones as he gleaned it from Person Finder, called Google's emergency service "indispensable." Not all the news he received was good, though: A friend was swept away by the tsunami.
"If you can't get information about your loved ones, you spend all your time searching. You cannot do anything else," said Kikuta, who at one point during the disaster passed out from exhaustion. "I am very grateful to Google."
THE INTERNET IN A DISASTER:
During last year's massive earthquake in Japan, millions of Japanese were unable to make phone calls. But they could send tweets and emails and check sites like Google Maps to help them navigate the disaster.
Why does the Internet seems more robust than phone networks?
"Phone networks are only designed for a certain number of users at any one time," said Rakesh Bharania, a member of Cisco Systems' emergency response operations. So in a crisis, when significantly more people than usual make phone calls simultaneously, the network becomes overloaded, Bharania said.
While data networks also see a surge in traffic, Bharania said, "what most people send on those networks are text - Web pages, tweets and so on." And text data uses a relatively smaller portion of bandwidth than voice data does, he said.
Explore further: YouTube helping with search for missing in Japan