USGS scientists field earthquake questions at Ofu-Olosenga town hall

Pago Pago, AMERICAN SAMOA — The US Geology Survey scientists currently in Manu’a are unclear as to how long the swarm of earthquakes will continue to occur around the Islands.

“Swarms like these can last hours to years, sometimes even longer,” said Dr Natalya Irma Deligne in response to questions during the town hall meeting for the Ofu and Olosega residents.

“It’s not nice news,” she said.

Adding that there are earthquake swarms in Hawaii that been happening since 2019 and the strength of the earthquakes vary.

During the meeting on Friday with residents of Ofu and Olosega, they were assured that the American Samoa Government is standing by on what other actions to take for the people of Manu’a over new information, whereas the Ofu-Olosega Islands volcano has been ruled out as the source of the ongoing Manuʻa Islands earthquake swarm.

Dr Deligne said data from seismometers installed in the Manuʻa Islands this week confirms that the ongoing earthquake activity is related to Taʻu Island volcano and not Ofu-Olosega.

“Accordingly, the USGS is lowering the volcano alert level to NORMAL and the aviation color code to GREEN for Ofu-Olosega. Taʻu Island remains at ADVISORY/ YELLOW.”

During the town hall meeting for Ofu and Olosega residents, Lt Governor Talauega Eleasalo Ale said the scientists are in Manu’a to try and get a better picture whether it’s a volcano, and if so how big and where exactly the volcano is.

“And if it’s just Fitiuta and Ta’u then it would be a less easy, but if in Olosega our efforts will focus here. This is one of the tasks by the Government but depending on data provided by the scientists as they have instruments that will determine the exact location and source of the earthquakes or volcano we are concerned about.

“Once that is determined then we will have a better picture and plan, but it does not stop efforts by the Government. At the moment we are working on evacuation roads to ensure [safety] when a disaster does occur.

Roads in Ofu will be resurfaced,” said Talauega.

Adding the main concerns in case of tsunami or a volcano is that people have somewhere to evacuate.

According to Talauega in any case if there is a need to evacuate the people of Ofu and Olosega then it will be done, and people need to be ready.

Educator Will Thompson, inquired about the opening of the new school year, given there is no definitive answer as the source of the quakes and also the students have been moved to Tutuila and he asked whether the Government has a plan to go back to remote learning?

“All the parents and community are affected by [what happens at] the school,” said Thompson.

The Lt Governor said at the moment, the plan is to proceed with opening of schools and operating in Manu’a, but it’s all subject to what happens and the results of the tests conducted by scientists.

“We have to be in limbo in these kinds of situations and be ready to adjust to change. I know that a lot of students here in Manu’a had moved to Tutuila and I don’t know if they are there for a long period or just for the summer.

“The expectation is that everyone will come back and then we’ll have schools as best as we can and we will continue to monitor any sudden changes in situations and will adjust accordingly.

“We are also looking as part of the evacuation plans on how to accommodate students in the event we have to have a mass evacuation, with schools in Tutuila and so forth, but for now, based on what I know here in Manu’a we’re hoping to have schools open,” said Talauega.

He said the work by the scientists will assist with their decisions as they cannot relocate people at the moment, because the Government plans are not finalized.

“If we learn new facts then there will definitely be changes. The top priority of our Government is the security and the well being of our people and if appears there is a risk we will act accordingly,” said Lemanu.

Dr Deligne gave an update and information about “what might happen with the current earthquakes that are being felt” in Manu’a. 

“It has been more than 4 weeks since the earthquakes started — our first report was on July 26. So these earthquakes are continuing as we feel them, we have been feeling them from the last couple of days.

“The earthquakes are definitely closer to the Manu’a islands than Vailu’ulu’u — so Vailuluu is completely out of the picture.”

She said the preliminary reports now also suggest that they’re closer to Tau island than to Ofu-Olosega.

“For the last few days since we had the instruments, they are detecting about 20 earthquakes in an hour not all these earthquakes were felt — most of them are much smaller, that’s about how many we’re picking up on our instruments.”

Adding that this is the work that the USGS along with the National Weather Service has done to date; and right now there are four USGS Hawaiian Volcano Observatory scientists in American Samoa.

“We all study volcanos, and two members are focused on earthquakes and myself and Drew are focused more on rocks and hazards as geologists. We have installed six very simple seismometers in American Samoa.

“We have four in the Manu’a Islands (Fitiuta, Olosega, Tau, Faleasao) and we also have two in Tutuila. “This week with the help of the National Weather Service, ASTCA, ASDHS, and many people we have installed three advanced seismometer in Tau village and Fitiuta and Ofu.”

Adding the advanced seismometer will allow USGS experts to determine where, how deep and how big the earthquakes are and experts will also look for signals that indicate whether these earthquakes are caused by volcanic processes.

“So that is the situation to date.”

According to Dr Deligne they will issue what it called a volcano activity notice.

“Right now we have issued the daily updates for the Manu’a islands and so that every day we have a new update which is just providing information of what’s happened in the last 24 hours and what our plans are.”

Dr Deligne said there are scenarios they see of what the future might hold.

“And we don’t know which path we’re on right now.

“The best-case scenario is the earthquakes go away. It does not mean that the experience and the journey we have been on goes away.

“There is a possibility that these earthquakes will become an eruption and the kind of eruption will depend on where it is.

“Another option is what we call a dry eruption on land so this would be an eruption up on the slope and a place with not too much ground water and it will be fairly collided in that area. You could see it from far away but the actual eruption will be fairly contained in a small area.

“The worst case scenario is a wet eruption which is a coastal eruption (near shore either on land or in the ocean) or a place with a lot of groundwater.”

The other scientist, Dr Jefferson Chang said right now they have a general idea that the earthquakes are closer to the east side of Tau.

“There are different steps that we’re taking and we know that some of them are repeating so when the earthquake happens it is because the rocks slipped.

“We found that some of these are happening at the same place, we don’t know where that same place is, but at least we know that they are not moving.

“So that is what we are looking at are movements either horizontal towards civilizations or vertical running out towards the air during the eruptions.”

Dr Delinge also explained the differences between eruption and explosion in response to questions at the town hall meeting.

In its latest update the USGS indicated that data from the seismometers installed this week allows seismologists (earthquake scientists) to estimate the number of earthquakes that people in the Manuʻa Islands might feel.

“In the past 24 hours, people may have felt approximately 34 earthquakes.

“The largest earthquake has a preliminary magnitude of 2.8, was strongly felt at 09:32:42 SST, and coincided with resident reports to the American Samoa Emergency Operations Center.

Including earthquakes that people would not feel, about 25 earthquakes per hour have occurred in the past day.

The satellite data check on August 27 showed no visible volcanic activity in the Taʻu Island area.

In the meantime, the Department of Public Works is clearing access roads for evacuation emergency exits in all of Manu’a.