According to the United States Geological Survey (USGS) the cities experiencing the strongest shaking—VIII (Severe) on the Mercalli intensity scale (MM)—were Concepción, Arauco, and Coronel.

[citation needed] The segment of the fault zone which ruptured in this earthquake was estimated to be over 700 km (430 mi) long with a displacement of almost 10 meters, or 120 years of accumulated plate movement.

[23] A research collaborative of Ohio State and other institutions have found, using GPS, that the earthquake shifted Santiago 28 cm (11 in) to the west-southwest and moved Concepción at least 3 metres (10 ft) to the west.

However, according to the University of Chile's Seismological Service, the seismic event was located 134 km (83 mi) off the coast of Tirúa, measuring a magnitude 6.9 ML.

[57] A magnitude 6.2 Mw aftershock struck the coast of Biobío, Chile at a shallow depth of 15.1 km (9.4 mi) on 1 June 2011 at 08:55 local time (12:55 UTC).

Strong shaking registering at VI on the Mercalli intensity scale was felt in Lebu, just 7 km (4.3 mi) south of the epicenter, lasting for approximately one minute.

[61] The earthquake was followed by a moderate magnitude 5.1 Mw tremor that occurred about 52 minutes later to the northeast of the main shock epicenter at an estimated depth of 26.9 km (16.7 mi).

[63] Seismologists estimate that the earthquake was so powerful that it may have shortened the length of the day by 1.26 microseconds and moved the Earth's figure axis by 2.7 milliarcseconds (about 8 cm).

[69] The earthquake also caused seiches to occur in Lake Pontchartrain to the north of New Orleans, United States, located nearly 7,500 kilometres (4,700 mi) from the epicenter of the quake.

[citation needed] According to an Associated Press Television News cameraman, some buildings collapsed in Santiago and there were power outages in parts of the city.

[8] On Sunday, 28 February, Ricardo Ortega, head of the Chilean Air Force, said commercial airline services had been partially re-established and aircraft were being allowed to land in Santiago.

The outgoing president didn't want to remind people of the Dictatorship years by militarizing the streets, thus failed to provide assistance on time to the city.

[citation needed] When the situation became unsustainable and all sectors of the population were demanding actions, the government authorized the use of the military to control the affected cities.

Neighbourhood vigilante groups, including one led by a public works employee with a gun license, and the few police present allow such behavior as residents' siphoning fuel from tanks at a petrol station, but step in if someone starts to attack a cash machine.

[117] Four hours after the earthquake, when the death count was still low, President Bachelet gave a press conference in which she informed the population of the situation and stated that Chile did not yet need international aid.

[118] On 28 February, President Bachelet said that her government had reached an agreement with the major supermarkets which would allow them to give away basic foodstuffs in stock to people affected by the earthquake.

[123] On 10 March the National Commission for Agricultural emergencies (CNEA) assured that milk and wheat prices would not rise, despite fears of lack of fuel supply for transport and harvest of these products.

[137] In the Americas, the warning extended to Chile (including Easter Island), Colombia, Costa Rica, Ecuador, El Salvador, Guatemala, Mexico, and Panama.

[137] Tsunami warnings were also in effect as far away as East and Southeast Asia including Japan, Indonesia, Hong Kong,[138] the Philippines, Russia and Taiwan.

"[145] Some 30 minutes after the first shock, consecutive tsunamis hit coastal towns, among which Constitución suffered the hardest damage, with maximum wave heights of approximately 24.1 m (79 ft),[5] and around 350 people killed.

[152][153] On 27 February, defense minister Francisco Vidal said that the Chilean Navy had made a mistake by not immediately issuing a tsunami warning after the earthquake, a step that could have helped coastal villagers flee to higher ground sooner.

[154] Mariano Rojas Bustos, then head of Chile's oceanographic service SHOA, which is part of the country's navy, was later fired for the organization's failure to provide clear warnings about the tsunami.

[162] By mid afternoon (local time), Civil Defence had downgraded the tsunami warning to an alert, while still advising that sea levels could change quickly for up to 24 hours from the initial surge.

To prepare for a possible tsunami, station personnel removed all Zodiac boats from the water and moved any materials from low-lying areas that waves could have swept away.

While no noticeable tsunami occurred at Palmer, the station tide monitor displayed bumps of several centimeters, signifying that a small wave had indeed reached the shores of Anvers Island.

The organization warned of the possibility of dangerous waves, strong ocean currents and foreshore flooding to occur on the east coast of Australia for several hours on Sunday.

[165] As a result of the warnings, patrolled beaches in New South Wales and Queensland remained closed (red flags) and lifeguards ushered people to leave the water.

[169] Réseau France Outre-mer in Papeete reported that a wave measuring less than 1 m (3 ft 3 in) passed east of the Gambier Islands with no damage, according to Monique Richeton, the mayor of Rikitea.

[169] Lieutenant Governor Ipulasi Aitofele Sunia urged residents not to rush to A'oloau, a high elevation area on Tutuila, as it could cause traffic jams, putting safety at risk.

The state tourism authorities announced they would be sending a letter to the CNN news network to protest the "alarming" way in which it had forecast a tsunami for the major tourist destination of Acapulco.