HVO reported that an earthquake swarm around Ta’u, in the Manu'a Islands of American Samoa, continued during 30 August-6 September. Less than 30 earthquakes per day were large enough to be felt by residents and many more earthquakes undetectable by humans were also recorded; no earthquakes were reportedly felt during 5-6 September. The data suggested that the earthquakes were consistently occurring in an area about 5-15 km off the N shore of the island, at depths of 10-15 km below the surface. There was no change in the frequency or size of earthquakes and the position of the swarm remained unchanged. USGS staff installed GPS equipment during 4-6 September. The Volcano Alert Level remained at Advisory and the Aviation Color Code remained at Yellow.

Geological Summary. The 10-km-wide Ta'u Island, located at the E end of the Samoan islands, is ringed by sea cliffs. It is the emergent portion of the large Lata shield volcano. A major flank collapse event around 22 ka resulted in the steep scarps on the southern side of the island. Two smaller shields were constructed along rift zones at the NW and NE tips of the island. The NW corner of the island has a tuff-cone complex that ejected large dunite xenoliths and coral blocks. Numerous Holocene post-caldera cones occur at the summit and on the flanks.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)