Chile's first elected right-wing president in 52 years won office promising to improve the economy, but says he will now be the "reconstruction president", urging citizens to "dry our tears and put our hands to work".
And leading by example, he met late into the night with his ministers after the day's ceremonies and touring of quake-hit regions, vowing to introduce his first proposals on relief and reconstruction to congress on Friday morning.
Moments before Pinera was sworn in on Thursday, three strong aftershocks hit the country, the strongest of which was 6.9 in magnitude, nearly matching the 7.0-magnitude quake that devastated Haiti on January 12.
In fact, the country was hit by more than a dozen significant aftershocks - three over magnitude-6 and six above magnitude-5 – on Thursday, demonstrating the challenges that face Pinera.
The inauguration ceremony went ahead despite some visiting dignitaries looking nervous, but lasted just 30 minutes.
The 60-year-old president and his ministers quickly took their oaths, and the audience of 2,000 headed for the exits and the hills, joining an evacuation called out of concern that the aftershocks would set off another tsunami.
The navy issued a tsunami alert along the coast and sirens sounded in Constitucion, one of the strongest-hit areas in the February 27 quake, while police ordered people away from beaches. The alert was later lifted.
Pinera left his guests soon after the inauguration to see for himself some of the areas most affected by the earthquake.
He flew to the inland city of Rancagua, which suffered additional damage during a strong aftershock on Thursday morning.
Lucia Newman, Al Jazeera's Latin America editor, said Pinera ordered troops in Rancagua to ensure there would be no repeat of scenes of looting that were seen in the city of Concepcion following the original earthquake.
Pinera said there were no reports of more deaths after Thursday's aftershocks, but the critical north-south highway suffered more damage in Rancagua, and violent waves hit at least two towns along the central coast, Pichilemu and Bucalemu, according to Rodrigo Hinzpeter, the new interior minister.
Returning to Santiago after his tour of the quake-hit areas, Pinera said: "Lots of people are still missing and I saw people in anguish today, as well as people with hope, who asked us not to abandon the search for those still missing.
|Pinera, in red, said he saw people 'in anguish' as he surveyed quake-hit Constitucion [EPA]
"Hundreds of thousands of Chileans have seen the earthquake or the tsunami destroy their dreams and livelihoods … everyone in Chile shares their distress and their loss."
Still he sounded an optimistic note, saying "tragedy and adversity, instead of getting us down, will fortify us".
"Tragedy and adversity never put down those who are strong, instead, it inspires them, allows them to confront their challenges, and allows them to find their destiny, their mission and their future," he said.
"For those who are suffering today … we will make the best possible efforts."
Thursday's handover of power from popular centre-leftist Michelle Bachelet was celebrated with relative austerity out of respect for those still mourning the dead.
Officials have identified 497 dead from the February 27 quake and tsunami, after revising down an earlier death toll of 802, which mistakenly included lists of the missing.
The fifth-strongest quake since 1900 also destroyed or heavily damaged at least 500,000 homes and broke apart highways and hospitals.