The governor's declaration which covers the entire territory is effective as of August 10, when the Emergency Operation Centers were activated by local authorities and follows Lemanu's site visit to Manu'a this week.
"The facts and evidence that have been gathered so far have supported a compelling reason to prioritise the protection of life and property," he said.
"By signing this Executive Order, I want to ensure that all local resources are made available to respond efficiently and effectively in case these eruptions worsen.
"I want to recognise and commend the first responders that are on the ground and have been standing by in Manu'a."
The quakes have been reported in Manu'a since July 26 and are still being felt.
The U.S Geological Survey has attributed the quakes to the Ta'u island volcano.
On his visit to the islands Lemanu was told the government needed to act.
Scientists says the seismographic activities are not primarily caused by the Vailulu'u seamount, American Samoa's most active submarine volcano.
However, they do not rule out that the cause of these tremors are due to other volcanic activity in the vicinity of the Manu'a islands.
During Lemanu's meeting with a village council on Ta'u island, there was a call for the government to provide a plan of action.
Ta'u chief, Sao Nua, said residents are in fear and they want to know what is the government's plan for displaced residents of Ta'u island.
Nua said residents hear the loud booms and tremors throughout the night "and feel our lives are in great danger."
Other residents suggested the government share its evacuation plans with residents as soon as possible.
The village of Faleasao told the governor they would need a consistent water supply on the mountainside, where there is currently none, to support evacuating further inland.
For residents on Ofu and Olosega islands their main concern was improving escape routes to higher ground, making them accessible by vehicles.
In response, Lemanu told residents - during the separate meetings - that the government will respond quickly to the immediate actions needed to ensure a swift and safe evacuation from coastal villages, villages with only one main road, and villages that need a good water source at evacuation sites.
He explained that more off-island resources, Federal personnel, scientists, and equipment are on the way to assist in gathering more information on locating the source of the seismicity and further examining whether these occurrences are linked to pre-eruption activity.
Lemanu also pointed out that local resources have been mobilised to assist throughout the Manu'a islands.
Photo Wiki Commons Caption: Manu'a island