A combination of natural disasters — an earthquake, then a tsunami — proved in many parts of this country too powerful for any preparation.

Many in earthquake-prone Japan had spent years practicing the safety checklist for those inevitable situations when the ground trembled and curled. But for those in the northeastern coastal areas, hit hardest by Friday’s 8.9-magnitude quake and resulting tsunami, this was a day — for many — where the only safe ground was too far away.

Japan on Saturday morning was still trying to tabulate the damage, the lives lost. But video, witness accounts and minute-by-minute Twitter updates have already given a picture of the mayhem. For those in Tokyo, the earthquake rattled buildings, shook offices. Computers spilled, lights gyrated and workers ducked under desks.

But in Sendai, the capital of Miyagi Prefecture, the tsunami turned a city into a confetti of shrapnel and wood — car scraps, engine parts, bricks. Eventually the wall of water that crashed ashore left behind a dark sludge that coated surrounding farm areas.

The earthquake struck off Japan’s northeastern coast at 2:46 p.m. local time. Just over an hour later, a wave — estimated to be taller than 20 feet — came roaring toward the shore. A video camera positioned atop Sendai’s airport showed how the tarmac was swallowed by rapids. Employees and travelers headed for the rooftops.

At the airport, fire soon burned from a small building positioned between the terminals. Cars and propeller airplanes were discarded by the waves, left among splintered wood, and aerial photos made them appear much like toys left out on the floor.

Towns in Miyagi Prefecture, Iwate Prefecture and Fukushima Prefecture were among the hardest-hit.

Video of those areas minutes after the tsunami made landfall gave an initial sense of the ferocity, if not the scope, of the disaster. One sport-utility vehicle was seen wedged between electric poles, pinned down as waves crashed over it. An area that once had been land looked like water. As waves partially submerged the vehicle, a house with a green roof came rushing by, surfing a crest of water.

In Natori city, houses were sliced in half — roofs here, living rooms there.

A Reuters photographer in Sendai snapped a photo at a library during either the initial quake or one of the aftershocks. The photo showed two boys, perhaps teenagers, clutching each other as small pieces of the ceiling rained down.

Throughout the country, particularly on the east coast, mobile networks were either downed or overloaded. But many people still found ways to access the Internet — and prayers, appeals for help and calls for the missing spread quickly by Twitter.

One Sendai resident, for instance, sent dozens of tweets in the hours after the tsunami — first telling of people who were safe and later asking for information about others.

“Phones are still dead,” one Twitter user in Sendai wrote. “I’m trying to call my brother, no connection yet.”

News stations spent much of the day showing a carousel of video from witnesses. One shot at a grocery store in Tokyo showed bottles crashing to the floor and some employees positioning themselves in front of the metal shelves to prevent further merchandise from tumbling.